Java example source code file (loopnode.cpp)
The loopnode.cpp Java example source code
/*
* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
#include "precompiled.hpp"
#include "ci/ciMethodData.hpp"
#include "compiler/compileLog.hpp"
#include "libadt/vectset.hpp"
#include "memory/allocation.inline.hpp"
#include "opto/addnode.hpp"
#include "opto/callnode.hpp"
#include "opto/connode.hpp"
#include "opto/divnode.hpp"
#include "opto/idealGraphPrinter.hpp"
#include "opto/loopnode.hpp"
#include "opto/mulnode.hpp"
#include "opto/rootnode.hpp"
#include "opto/superword.hpp"
//=============================================================================
//------------------------------is_loop_iv-------------------------------------
// Determine if a node is Counted loop induction variable.
// The method is declared in node.hpp.
const Node* Node::is_loop_iv() const {
if (this->is_Phi() && !this->as_Phi()->is_copy() &&
this->as_Phi()->region()->is_CountedLoop() &&
this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
return this;
} else {
return NULL;
}
}
//=============================================================================
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void LoopNode::dump_spec(outputStream *st) const {
if (is_inner_loop()) st->print( "inner " );
if (is_partial_peel_loop()) st->print( "partial_peel " );
if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
}
#endif
//------------------------------is_valid_counted_loop-------------------------
bool LoopNode::is_valid_counted_loop() const {
if (is_CountedLoop()) {
CountedLoopNode* l = as_CountedLoop();
CountedLoopEndNode* le = l->loopexit();
if (le != NULL &&
le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
Node* phi = l->phi();
Node* exit = le->proj_out(0 /* false */);
if (exit != NULL && exit->Opcode() == Op_IfFalse &&
phi != NULL && phi->is_Phi() &&
phi->in(LoopNode::LoopBackControl) == l->incr() &&
le->loopnode() == l && le->stride_is_con()) {
return true;
}
}
}
return false;
}
//------------------------------get_early_ctrl---------------------------------
// Compute earliest legal control
Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
uint i;
Node *early;
if (n->in(0) && !n->is_expensive()) {
early = n->in(0);
if (!early->is_CFG()) // Might be a non-CFG multi-def
early = get_ctrl(early); // So treat input as a straight data input
i = 1;
} else {
early = get_ctrl(n->in(1));
i = 2;
}
uint e_d = dom_depth(early);
assert( early, "" );
for (; i < n->req(); i++) {
Node *cin = get_ctrl(n->in(i));
assert( cin, "" );
// Keep deepest dominator depth
uint c_d = dom_depth(cin);
if (c_d > e_d) { // Deeper guy?
early = cin; // Keep deepest found so far
e_d = c_d;
} else if (c_d == e_d && // Same depth?
early != cin) { // If not equal, must use slower algorithm
// If same depth but not equal, one _must_ dominate the other
// and we want the deeper (i.e., dominated) guy.
Node *n1 = early;
Node *n2 = cin;
while (1) {
n1 = idom(n1); // Walk up until break cycle
n2 = idom(n2);
if (n1 == cin || // Walked early up to cin
dom_depth(n2) < c_d)
break; // early is deeper; keep him
if (n2 == early || // Walked cin up to early
dom_depth(n1) < c_d) {
early = cin; // cin is deeper; keep him
break;
}
}
e_d = dom_depth(early); // Reset depth register cache
}
}
// Return earliest legal location
assert(early == find_non_split_ctrl(early), "unexpected early control");
if (n->is_expensive()) {
assert(n->in(0), "should have control input");
early = get_early_ctrl_for_expensive(n, early);
}
return early;
}
//------------------------------get_early_ctrl_for_expensive---------------------------------
// Move node up the dominator tree as high as legal while still beneficial
Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
assert(OptimizeExpensiveOps, "optimization off?");
Node* ctl = n->in(0);
assert(ctl->is_CFG(), "expensive input 0 must be cfg");
uint min_dom_depth = dom_depth(earliest);
#ifdef ASSERT
if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
}
#endif
if (dom_depth(ctl) < min_dom_depth) {
return earliest;
}
while (1) {
Node *next = ctl;
// Moving the node out of a loop on the projection of a If
// confuses loop predication. So once we hit a Loop in a If branch
// that doesn't branch to an UNC, we stop. The code that process
// expensive nodes will notice the loop and skip over it to try to
// move the node further up.
if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
break;
}
next = idom(ctl->in(1)->in(0));
} else if (ctl->is_Proj()) {
// We only move it up along a projection if the projection is
// the single control projection for its parent: same code path,
// if it's a If with UNC or fallthrough of a call.
Node* parent_ctl = ctl->in(0);
if (parent_ctl == NULL) {
break;
} else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
} else if (parent_ctl->is_If()) {
if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
break;
}
assert(idom(ctl) == parent_ctl, "strange");
next = idom(parent_ctl);
} else if (ctl->is_CatchProj()) {
if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
break;
}
assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
next = parent_ctl->in(0)->in(0)->in(0);
} else {
// Check if parent control has a single projection (this
// control is the only possible successor of the parent
// control). If so, we can try to move the node above the
// parent control.
int nb_ctl_proj = 0;
for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
Node *p = parent_ctl->fast_out(i);
if (p->is_Proj() && p->is_CFG()) {
nb_ctl_proj++;
if (nb_ctl_proj > 1) {
break;
}
}
}
if (nb_ctl_proj > 1) {
break;
}
assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
assert(idom(ctl) == parent_ctl, "strange");
next = idom(parent_ctl);
}
} else {
next = idom(ctl);
}
if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
break;
}
ctl = next;
}
if (ctl != n->in(0)) {
_igvn.hash_delete(n);
n->set_req(0, ctl);
_igvn.hash_insert(n);
}
return ctl;
}
//------------------------------set_early_ctrl---------------------------------
// Set earliest legal control
void PhaseIdealLoop::set_early_ctrl( Node *n ) {
Node *early = get_early_ctrl(n);
// Record earliest legal location
set_ctrl(n, early);
}
//------------------------------set_subtree_ctrl-------------------------------
// set missing _ctrl entries on new nodes
void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
// Already set? Get out.
if( _nodes[n->_idx] ) return;
// Recursively set _nodes array to indicate where the Node goes
uint i;
for( i = 0; i < n->req(); ++i ) {
Node *m = n->in(i);
if( m && m != C->root() )
set_subtree_ctrl( m );
}
// Fixup self
set_early_ctrl( n );
}
//------------------------------is_counted_loop--------------------------------
bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
PhaseGVN *gvn = &_igvn;
// Counted loop head must be a good RegionNode with only 3 not NULL
// control input edges: Self, Entry, LoopBack.
if (x->in(LoopNode::Self) == NULL || x->req() != 3)
return false;
Node *init_control = x->in(LoopNode::EntryControl);
Node *back_control = x->in(LoopNode::LoopBackControl);
if (init_control == NULL || back_control == NULL) // Partially dead
return false;
// Must also check for TOP when looking for a dead loop
if (init_control->is_top() || back_control->is_top())
return false;
// Allow funny placement of Safepoint
if (back_control->Opcode() == Op_SafePoint)
back_control = back_control->in(TypeFunc::Control);
// Controlling test for loop
Node *iftrue = back_control;
uint iftrue_op = iftrue->Opcode();
if (iftrue_op != Op_IfTrue &&
iftrue_op != Op_IfFalse)
// I have a weird back-control. Probably the loop-exit test is in
// the middle of the loop and I am looking at some trailing control-flow
// merge point. To fix this I would have to partially peel the loop.
return false; // Obscure back-control
// Get boolean guarding loop-back test
Node *iff = iftrue->in(0);
if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
return false;
BoolNode *test = iff->in(1)->as_Bool();
BoolTest::mask bt = test->_test._test;
float cl_prob = iff->as_If()->_prob;
if (iftrue_op == Op_IfFalse) {
bt = BoolTest(bt).negate();
cl_prob = 1.0 - cl_prob;
}
// Get backedge compare
Node *cmp = test->in(1);
int cmp_op = cmp->Opcode();
if (cmp_op != Op_CmpI)
return false; // Avoid pointer & float compares
// Find the trip-counter increment & limit. Limit must be loop invariant.
Node *incr = cmp->in(1);
Node *limit = cmp->in(2);
// ---------
// need 'loop()' test to tell if limit is loop invariant
// ---------
if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
Node *tmp = incr; // Then reverse order into the CmpI
incr = limit;
limit = tmp;
bt = BoolTest(bt).commute(); // And commute the exit test
}
if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
return false;
if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
return false;
Node* phi_incr = NULL;
// Trip-counter increment must be commutative & associative.
if (incr->is_Phi()) {
if (incr->as_Phi()->region() != x || incr->req() != 3)
return false; // Not simple trip counter expression
phi_incr = incr;
incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
return false;
}
Node* trunc1 = NULL;
Node* trunc2 = NULL;
const TypeInt* iv_trunc_t = NULL;
if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
return false; // Funny increment opcode
}
assert(incr->Opcode() == Op_AddI, "wrong increment code");
// Get merge point
Node *xphi = incr->in(1);
Node *stride = incr->in(2);
if (!stride->is_Con()) { // Oops, swap these
if (!xphi->is_Con()) // Is the other guy a constant?
return false; // Nope, unknown stride, bail out
Node *tmp = xphi; // 'incr' is commutative, so ok to swap
xphi = stride;
stride = tmp;
}
// Stride must be constant
int stride_con = stride->get_int();
if (stride_con == 0)
return false; // missed some peephole opt
if (!xphi->is_Phi())
return false; // Too much math on the trip counter
if (phi_incr != NULL && phi_incr != xphi)
return false;
PhiNode *phi = xphi->as_Phi();
// Phi must be of loop header; backedge must wrap to increment
if (phi->region() != x)
return false;
if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) {
return false;
}
Node *init_trip = phi->in(LoopNode::EntryControl);
// If iv trunc type is smaller than int, check for possible wrap.
if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
assert(trunc1 != NULL, "must have found some truncation");
// Get a better type for the phi (filtered thru if's)
const TypeInt* phi_ft = filtered_type(phi);
// Can iv take on a value that will wrap?
//
// Ensure iv's limit is not within "stride" of the wrap value.
//
// Example for "short" type
// Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
// If the stride is +10, then the last value of the induction
// variable before the increment (phi_ft->_hi) must be
// <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
// ensure no truncation occurs after the increment.
if (stride_con > 0) {
if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
iv_trunc_t->_lo > phi_ft->_lo) {
return false; // truncation may occur
}
} else if (stride_con < 0) {
if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
iv_trunc_t->_hi < phi_ft->_hi) {
return false; // truncation may occur
}
}
// No possibility of wrap so truncation can be discarded
// Promote iv type to Int
} else {
assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
}
// If the condition is inverted and we will be rolling
// through MININT to MAXINT, then bail out.
if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
// Odd stride
bt == BoolTest::ne && stride_con != 1 && stride_con != -1 ||
// Count down loop rolls through MAXINT
(bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 ||
// Count up loop rolls through MININT
(bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) {
return false; // Bail out
}
const TypeInt* init_t = gvn->type(init_trip)->is_int();
const TypeInt* limit_t = gvn->type(limit)->is_int();
if (stride_con > 0) {
jlong init_p = (jlong)init_t->_lo + stride_con;
if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
return false; // cyclic loop or this loop trips only once
} else {
jlong init_p = (jlong)init_t->_hi + stride_con;
if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
return false; // cyclic loop or this loop trips only once
}
// =================================================
// ---- SUCCESS! Found A Trip-Counted Loop! -----
//
assert(x->Opcode() == Op_Loop, "regular loops only");
C->print_method(PHASE_BEFORE_CLOOPS, 3);
Node *hook = new (C) Node(6);
if (LoopLimitCheck) {
// ===================================================
// Generate loop limit check to avoid integer overflow
// in cases like next (cyclic loops):
//
// for (i=0; i <= max_jint; i++) {}
// for (i=0; i < max_jint; i+=2) {}
//
//
// Limit check predicate depends on the loop test:
//
// for(;i != limit; i++) --> limit <= (max_jint)
// for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1)
// for(;i <= limit; i+=stride) --> limit <= (max_jint - stride )
//
// Check if limit is excluded to do more precise int overflow check.
bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
// If compare points directly to the phi we need to adjust
// the compare so that it points to the incr. Limit have
// to be adjusted to keep trip count the same and the
// adjusted limit should be checked for int overflow.
if (phi_incr != NULL) {
stride_m += stride_con;
}
if (limit->is_Con()) {
int limit_con = limit->get_int();
if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
(stride_con < 0 && limit_con < (min_jint - stride_m))) {
// Bailout: it could be integer overflow.
return false;
}
} else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
(stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
// Limit's type may satisfy the condition, for example,
// when it is an array length.
} else {
// Generate loop's limit check.
// Loop limit check predicate should be near the loop.
ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
if (!limit_check_proj) {
// The limit check predicate is not generated if this method trapped here before.
#ifdef ASSERT
if (TraceLoopLimitCheck) {
tty->print("missing loop limit check:");
loop->dump_head();
x->dump(1);
}
#endif
return false;
}
IfNode* check_iff = limit_check_proj->in(0)->as_If();
Node* cmp_limit;
Node* bol;
if (stride_con > 0) {
cmp_limit = new (C) CmpINode(limit, _igvn.intcon(max_jint - stride_m));
bol = new (C) BoolNode(cmp_limit, BoolTest::le);
} else {
cmp_limit = new (C) CmpINode(limit, _igvn.intcon(min_jint - stride_m));
bol = new (C) BoolNode(cmp_limit, BoolTest::ge);
}
cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
bol = _igvn.register_new_node_with_optimizer(bol);
set_subtree_ctrl(bol);
// Replace condition in original predicate but preserve Opaque node
// so that previous predicates could be found.
assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
Node* opq = check_iff->in(1)->in(1);
_igvn.hash_delete(opq);
opq->set_req(1, bol);
// Update ctrl.
set_ctrl(opq, check_iff->in(0));
set_ctrl(check_iff->in(1), check_iff->in(0));
#ifndef PRODUCT
// report that the loop predication has been actually performed
// for this loop
if (TraceLoopLimitCheck) {
tty->print_cr("Counted Loop Limit Check generated:");
debug_only( bol->dump(2); )
}
#endif
}
if (phi_incr != NULL) {
// If compare points directly to the phi we need to adjust
// the compare so that it points to the incr. Limit have
// to be adjusted to keep trip count the same and we
// should avoid int overflow.
//
// i = init; do {} while(i++ < limit);
// is converted to
// i = init; do {} while(++i < limit+1);
//
limit = gvn->transform(new (C) AddINode(limit, stride));
}
// Now we need to canonicalize loop condition.
if (bt == BoolTest::ne) {
assert(stride_con == 1 || stride_con == -1, "simple increment only");
// 'ne' can be replaced with 'lt' only when init < limit.
if (stride_con > 0 && init_t->_hi < limit_t->_lo)
bt = BoolTest::lt;
// 'ne' can be replaced with 'gt' only when init > limit.
if (stride_con < 0 && init_t->_lo > limit_t->_hi)
bt = BoolTest::gt;
}
if (incl_limit) {
// The limit check guaranties that 'limit <= (max_jint - stride)' so
// we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
//
Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
limit = gvn->transform(new (C) AddINode(limit, one));
if (bt == BoolTest::le)
bt = BoolTest::lt;
else if (bt == BoolTest::ge)
bt = BoolTest::gt;
else
ShouldNotReachHere();
}
set_subtree_ctrl( limit );
} else { // LoopLimitCheck
// If compare points to incr, we are ok. Otherwise the compare
// can directly point to the phi; in this case adjust the compare so that
// it points to the incr by adjusting the limit.
if (cmp->in(1) == phi || cmp->in(2) == phi)
limit = gvn->transform(new (C) AddINode(limit,stride));
// trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
// Final value for iterator should be: trip_count * stride + init_trip.
Node *one_p = gvn->intcon( 1);
Node *one_m = gvn->intcon(-1);
Node *trip_count = NULL;
switch( bt ) {
case BoolTest::eq:
ShouldNotReachHere();
case BoolTest::ne: // Ahh, the case we desire
if (stride_con == 1)
trip_count = gvn->transform(new (C) SubINode(limit,init_trip));
else if (stride_con == -1)
trip_count = gvn->transform(new (C) SubINode(init_trip,limit));
else
ShouldNotReachHere();
set_subtree_ctrl(trip_count);
//_loop.map(trip_count->_idx,loop(limit));
break;
case BoolTest::le: // Maybe convert to '<' case
limit = gvn->transform(new (C) AddINode(limit,one_p));
set_subtree_ctrl( limit );
hook->init_req(4, limit);
bt = BoolTest::lt;
// Make the new limit be in the same loop nest as the old limit
//_loop.map(limit->_idx,limit_loop);
// Fall into next case
case BoolTest::lt: { // Maybe convert to '!=' case
if (stride_con < 0) // Count down loop rolls through MAXINT
ShouldNotReachHere();
Node *range = gvn->transform(new (C) SubINode(limit,init_trip));
set_subtree_ctrl( range );
hook->init_req(0, range);
Node *bias = gvn->transform(new (C) AddINode(range,stride));
set_subtree_ctrl( bias );
hook->init_req(1, bias);
Node *bias1 = gvn->transform(new (C) AddINode(bias,one_m));
set_subtree_ctrl( bias1 );
hook->init_req(2, bias1);
trip_count = gvn->transform(new (C) DivINode(0,bias1,stride));
set_subtree_ctrl( trip_count );
hook->init_req(3, trip_count);
break;
}
case BoolTest::ge: // Maybe convert to '>' case
limit = gvn->transform(new (C) AddINode(limit,one_m));
set_subtree_ctrl( limit );
hook->init_req(4 ,limit);
bt = BoolTest::gt;
// Make the new limit be in the same loop nest as the old limit
//_loop.map(limit->_idx,limit_loop);
// Fall into next case
case BoolTest::gt: { // Maybe convert to '!=' case
if (stride_con > 0) // count up loop rolls through MININT
ShouldNotReachHere();
Node *range = gvn->transform(new (C) SubINode(limit,init_trip));
set_subtree_ctrl( range );
hook->init_req(0, range);
Node *bias = gvn->transform(new (C) AddINode(range,stride));
set_subtree_ctrl( bias );
hook->init_req(1, bias);
Node *bias1 = gvn->transform(new (C) AddINode(bias,one_p));
set_subtree_ctrl( bias1 );
hook->init_req(2, bias1);
trip_count = gvn->transform(new (C) DivINode(0,bias1,stride));
set_subtree_ctrl( trip_count );
hook->init_req(3, trip_count);
break;
}
} // switch( bt )
Node *span = gvn->transform(new (C) MulINode(trip_count,stride));
set_subtree_ctrl( span );
hook->init_req(5, span);
limit = gvn->transform(new (C) AddINode(span,init_trip));
set_subtree_ctrl( limit );
} // LoopLimitCheck
// Check for SafePoint on backedge and remove
Node *sfpt = x->in(LoopNode::LoopBackControl);
if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
lazy_replace( sfpt, iftrue );
if (loop->_safepts != NULL) {
loop->_safepts->yank(sfpt);
}
loop->_tail = iftrue;
}
// Build a canonical trip test.
// Clone code, as old values may be in use.
incr = incr->clone();
incr->set_req(1,phi);
incr->set_req(2,stride);
incr = _igvn.register_new_node_with_optimizer(incr);
set_early_ctrl( incr );
_igvn.hash_delete(phi);
phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
// If phi type is more restrictive than Int, raise to
// Int to prevent (almost) infinite recursion in igvn
// which can only handle integer types for constants or minint..maxint.
if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
nphi = _igvn.register_new_node_with_optimizer(nphi);
set_ctrl(nphi, get_ctrl(phi));
_igvn.replace_node(phi, nphi);
phi = nphi->as_Phi();
}
cmp = cmp->clone();
cmp->set_req(1,incr);
cmp->set_req(2,limit);
cmp = _igvn.register_new_node_with_optimizer(cmp);
set_ctrl(cmp, iff->in(0));
test = test->clone()->as_Bool();
(*(BoolTest*)&test->_test)._test = bt;
test->set_req(1,cmp);
_igvn.register_new_node_with_optimizer(test);
set_ctrl(test, iff->in(0));
// Replace the old IfNode with a new LoopEndNode
Node *lex = _igvn.register_new_node_with_optimizer(new (C) CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
IfNode *le = lex->as_If();
uint dd = dom_depth(iff);
set_idom(le, le->in(0), dd); // Update dominance for loop exit
set_loop(le, loop);
// Get the loop-exit control
Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
// Need to swap loop-exit and loop-back control?
if (iftrue_op == Op_IfFalse) {
Node *ift2=_igvn.register_new_node_with_optimizer(new (C) IfTrueNode (le));
Node *iff2=_igvn.register_new_node_with_optimizer(new (C) IfFalseNode(le));
loop->_tail = back_control = ift2;
set_loop(ift2, loop);
set_loop(iff2, get_loop(iffalse));
// Lazy update of 'get_ctrl' mechanism.
lazy_replace_proj( iffalse, iff2 );
lazy_replace_proj( iftrue, ift2 );
// Swap names
iffalse = iff2;
iftrue = ift2;
} else {
_igvn.hash_delete(iffalse);
_igvn.hash_delete(iftrue);
iffalse->set_req_X( 0, le, &_igvn );
iftrue ->set_req_X( 0, le, &_igvn );
}
set_idom(iftrue, le, dd+1);
set_idom(iffalse, le, dd+1);
assert(iff->outcnt() == 0, "should be dead now");
lazy_replace( iff, le ); // fix 'get_ctrl'
// Now setup a new CountedLoopNode to replace the existing LoopNode
CountedLoopNode *l = new (C) CountedLoopNode(init_control, back_control);
l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
// The following assert is approximately true, and defines the intention
// of can_be_counted_loop. It fails, however, because phase->type
// is not yet initialized for this loop and its parts.
//assert(l->can_be_counted_loop(this), "sanity");
_igvn.register_new_node_with_optimizer(l);
set_loop(l, loop);
loop->_head = l;
// Fix all data nodes placed at the old loop head.
// Uses the lazy-update mechanism of 'get_ctrl'.
lazy_replace( x, l );
set_idom(l, init_control, dom_depth(x));
// Check for immediately preceding SafePoint and remove
Node *sfpt2 = le->in(0);
if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) {
lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
if (loop->_safepts != NULL) {
loop->_safepts->yank(sfpt2);
}
}
// Free up intermediate goo
_igvn.remove_dead_node(hook);
#ifdef ASSERT
assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
#endif
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Counted ");
loop->dump_head();
}
#endif
C->print_method(PHASE_AFTER_CLOOPS, 3);
return true;
}
//----------------------exact_limit-------------------------------------------
Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
assert(loop->_head->is_CountedLoop(), "");
CountedLoopNode *cl = loop->_head->as_CountedLoop();
assert(cl->is_valid_counted_loop(), "");
if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
cl->limit()->Opcode() == Op_LoopLimit) {
// Old code has exact limit (it could be incorrect in case of int overflow).
// Loop limit is exact with stride == 1. And loop may already have exact limit.
return cl->limit();
}
Node *limit = NULL;
#ifdef ASSERT
BoolTest::mask bt = cl->loopexit()->test_trip();
assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
#endif
if (cl->has_exact_trip_count()) {
// Simple case: loop has constant boundaries.
// Use jlongs to avoid integer overflow.
int stride_con = cl->stride_con();
jlong init_con = cl->init_trip()->get_int();
jlong limit_con = cl->limit()->get_int();
julong trip_cnt = cl->trip_count();
jlong final_con = init_con + trip_cnt*stride_con;
int final_int = (int)final_con;
// The final value should be in integer range since the loop
// is counted and the limit was checked for overflow.
assert(final_con == (jlong)final_int, "final value should be integer");
limit = _igvn.intcon(final_int);
} else {
// Create new LoopLimit node to get exact limit (final iv value).
limit = new (C) LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
register_new_node(limit, cl->in(LoopNode::EntryControl));
}
assert(limit != NULL, "sanity");
return limit;
}
//------------------------------Ideal------------------------------------------
// Return a node which is more "ideal" than the current node.
// Attempt to convert into a counted-loop.
Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (!can_be_counted_loop(phase)) {
phase->C->set_major_progress();
}
return RegionNode::Ideal(phase, can_reshape);
}
//=============================================================================
//------------------------------Ideal------------------------------------------
// Return a node which is more "ideal" than the current node.
// Attempt to convert into a counted-loop.
Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
return RegionNode::Ideal(phase, can_reshape);
}
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void CountedLoopNode::dump_spec(outputStream *st) const {
LoopNode::dump_spec(st);
if (stride_is_con()) {
st->print("stride: %d ",stride_con());
}
if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
if (is_main_loop()) st->print("main of N%d", _idx);
if (is_post_loop()) st->print("post of N%d", _main_idx);
}
#endif
//=============================================================================
int CountedLoopEndNode::stride_con() const {
return stride()->bottom_type()->is_int()->get_con();
}
//=============================================================================
//------------------------------Value-----------------------------------------
const Type *LoopLimitNode::Value( PhaseTransform *phase ) const {
const Type* init_t = phase->type(in(Init));
const Type* limit_t = phase->type(in(Limit));
const Type* stride_t = phase->type(in(Stride));
// Either input is TOP ==> the result is TOP
if (init_t == Type::TOP) return Type::TOP;
if (limit_t == Type::TOP) return Type::TOP;
if (stride_t == Type::TOP) return Type::TOP;
int stride_con = stride_t->is_int()->get_con();
if (stride_con == 1)
return NULL; // Identity
if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
// Use jlongs to avoid integer overflow.
jlong init_con = init_t->is_int()->get_con();
jlong limit_con = limit_t->is_int()->get_con();
int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
jlong final_con = init_con + stride_con*trip_count;
int final_int = (int)final_con;
// The final value should be in integer range since the loop
// is counted and the limit was checked for overflow.
assert(final_con == (jlong)final_int, "final value should be integer");
return TypeInt::make(final_int);
}
return bottom_type(); // TypeInt::INT
}
//------------------------------Ideal------------------------------------------
// Return a node which is more "ideal" than the current node.
Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (phase->type(in(Init)) == Type::TOP ||
phase->type(in(Limit)) == Type::TOP ||
phase->type(in(Stride)) == Type::TOP)
return NULL; // Dead
int stride_con = phase->type(in(Stride))->is_int()->get_con();
if (stride_con == 1)
return NULL; // Identity
if (in(Init)->is_Con() && in(Limit)->is_Con())
return NULL; // Value
// Delay following optimizations until all loop optimizations
// done to keep Ideal graph simple.
if (!can_reshape || phase->C->major_progress())
return NULL;
const TypeInt* init_t = phase->type(in(Init) )->is_int();
const TypeInt* limit_t = phase->type(in(Limit))->is_int();
int stride_p;
jlong lim, ini;
julong max;
if (stride_con > 0) {
stride_p = stride_con;
lim = limit_t->_hi;
ini = init_t->_lo;
max = (julong)max_jint;
} else {
stride_p = -stride_con;
lim = init_t->_hi;
ini = limit_t->_lo;
max = (julong)min_jint;
}
julong range = lim - ini + stride_p;
if (range <= max) {
// Convert to integer expression if it is not overflow.
Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
Node *range = phase->transform(new (phase->C) SubINode(in(Limit), in(Init)));
Node *bias = phase->transform(new (phase->C) AddINode(range, stride_m));
Node *trip = phase->transform(new (phase->C) DivINode(0, bias, in(Stride)));
Node *span = phase->transform(new (phase->C) MulINode(trip, in(Stride)));
return new (phase->C) AddINode(span, in(Init)); // exact limit
}
if (is_power_of_2(stride_p) || // divisor is 2^n
!Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
// Convert to long expression to avoid integer overflow
// and let igvn optimizer convert this division.
//
Node* init = phase->transform( new (phase->C) ConvI2LNode(in(Init)));
Node* limit = phase->transform( new (phase->C) ConvI2LNode(in(Limit)));
Node* stride = phase->longcon(stride_con);
Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
Node *range = phase->transform(new (phase->C) SubLNode(limit, init));
Node *bias = phase->transform(new (phase->C) AddLNode(range, stride_m));
Node *span;
if (stride_con > 0 && is_power_of_2(stride_p)) {
// bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
// and avoid generating rounding for division. Zero trip guard should
// guarantee that init < limit but sometimes the guard is missing and
// we can get situation when init > limit. Note, for the empty loop
// optimization zero trip guard is generated explicitly which leaves
// only RCE predicate where exact limit is used and the predicate
// will simply fail forcing recompilation.
Node* neg_stride = phase->longcon(-stride_con);
span = phase->transform(new (phase->C) AndLNode(bias, neg_stride));
} else {
Node *trip = phase->transform(new (phase->C) DivLNode(0, bias, stride));
span = phase->transform(new (phase->C) MulLNode(trip, stride));
}
// Convert back to int
Node *span_int = phase->transform(new (phase->C) ConvL2INode(span));
return new (phase->C) AddINode(span_int, in(Init)); // exact limit
}
return NULL; // No progress
}
//------------------------------Identity---------------------------------------
// If stride == 1 return limit node.
Node *LoopLimitNode::Identity( PhaseTransform *phase ) {
int stride_con = phase->type(in(Stride))->is_int()->get_con();
if (stride_con == 1 || stride_con == -1)
return in(Limit);
return this;
}
//=============================================================================
//----------------------match_incr_with_optional_truncation--------------------
// Match increment with optional truncation:
// CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
// Return NULL for failure. Success returns the increment node.
Node* CountedLoopNode::match_incr_with_optional_truncation(
Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
// Quick cutouts:
if (expr == NULL || expr->req() != 3) return NULL;
Node *t1 = NULL;
Node *t2 = NULL;
const TypeInt* trunc_t = TypeInt::INT;
Node* n1 = expr;
int n1op = n1->Opcode();
// Try to strip (n1 & M) or (n1 << N >> N) from n1.
if (n1op == Op_AndI &&
n1->in(2)->is_Con() &&
n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
// %%% This check should match any mask of 2**K-1.
t1 = n1;
n1 = t1->in(1);
n1op = n1->Opcode();
trunc_t = TypeInt::CHAR;
} else if (n1op == Op_RShiftI &&
n1->in(1) != NULL &&
n1->in(1)->Opcode() == Op_LShiftI &&
n1->in(2) == n1->in(1)->in(2) &&
n1->in(2)->is_Con()) {
jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
// %%% This check should match any shift in [1..31].
if (shift == 16 || shift == 8) {
t1 = n1;
t2 = t1->in(1);
n1 = t2->in(1);
n1op = n1->Opcode();
if (shift == 16) {
trunc_t = TypeInt::SHORT;
} else if (shift == 8) {
trunc_t = TypeInt::BYTE;
}
}
}
// If (maybe after stripping) it is an AddI, we won:
if (n1op == Op_AddI) {
*trunc1 = t1;
*trunc2 = t2;
*trunc_type = trunc_t;
return n1;
}
// failed
return NULL;
}
//------------------------------filtered_type--------------------------------
// Return a type based on condition control flow
// A successful return will be a type that is restricted due
// to a series of dominating if-tests, such as:
// if (i < 10) {
// if (i > 0) {
// here: "i" type is [1..10)
// }
// }
// or a control flow merge
// if (i < 10) {
// do {
// phi( , ) -- at top of loop type is [min_int..10)
// i = ?
// } while ( i < 10)
//
const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
assert(n && n->bottom_type()->is_int(), "must be int");
const TypeInt* filtered_t = NULL;
if (!n->is_Phi()) {
assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
filtered_t = filtered_type_from_dominators(n, n_ctrl);
} else {
Node* phi = n->as_Phi();
Node* region = phi->in(0);
assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
if (region && region != C->top()) {
for (uint i = 1; i < phi->req(); i++) {
Node* val = phi->in(i);
Node* use_c = region->in(i);
const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
if (val_t != NULL) {
if (filtered_t == NULL) {
filtered_t = val_t;
} else {
filtered_t = filtered_t->meet(val_t)->is_int();
}
}
}
}
}
const TypeInt* n_t = _igvn.type(n)->is_int();
if (filtered_t != NULL) {
n_t = n_t->join(filtered_t)->is_int();
}
return n_t;
}
//------------------------------filtered_type_from_dominators--------------------------------
// Return a possibly more restrictive type for val based on condition control flow of dominators
const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
if (val->is_Con()) {
return val->bottom_type()->is_int();
}
uint if_limit = 10; // Max number of dominating if's visited
const TypeInt* rtn_t = NULL;
if (use_ctrl && use_ctrl != C->top()) {
Node* val_ctrl = get_ctrl(val);
uint val_dom_depth = dom_depth(val_ctrl);
Node* pred = use_ctrl;
uint if_cnt = 0;
while (if_cnt < if_limit) {
if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
if_cnt++;
const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
if (if_t != NULL) {
if (rtn_t == NULL) {
rtn_t = if_t;
} else {
rtn_t = rtn_t->join(if_t)->is_int();
}
}
}
pred = idom(pred);
if (pred == NULL || pred == C->top()) {
break;
}
// Stop if going beyond definition block of val
if (dom_depth(pred) < val_dom_depth) {
break;
}
}
}
return rtn_t;
}
//------------------------------dump_spec--------------------------------------
// Dump special per-node info
#ifndef PRODUCT
void CountedLoopEndNode::dump_spec(outputStream *st) const {
if( in(TestValue)->is_Bool() ) {
BoolTest bt( test_trip()); // Added this for g++.
st->print("[");
bt.dump_on(st);
st->print("]");
}
st->print(" ");
IfNode::dump_spec(st);
}
#endif
//=============================================================================
//------------------------------is_member--------------------------------------
// Is 'l' a member of 'this'?
int IdealLoopTree::is_member( const IdealLoopTree *l ) const {
while( l->_nest > _nest ) l = l->_parent;
return l == this;
}
//------------------------------set_nest---------------------------------------
// Set loop tree nesting depth. Accumulate _has_call bits.
int IdealLoopTree::set_nest( uint depth ) {
_nest = depth;
int bits = _has_call;
if( _child ) bits |= _child->set_nest(depth+1);
if( bits ) _has_call = 1;
if( _next ) bits |= _next ->set_nest(depth );
return bits;
}
//------------------------------split_fall_in----------------------------------
// Split out multiple fall-in edges from the loop header. Move them to a
// private RegionNode before the loop. This becomes the loop landing pad.
void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
PhaseIterGVN &igvn = phase->_igvn;
uint i;
// Make a new RegionNode to be the landing pad.
Node *landing_pad = new (phase->C) RegionNode( fall_in_cnt+1 );
phase->set_loop(landing_pad,_parent);
// Gather all the fall-in control paths into the landing pad
uint icnt = fall_in_cnt;
uint oreq = _head->req();
for( i = oreq-1; i>0; i-- )
if( !phase->is_member( this, _head->in(i) ) )
landing_pad->set_req(icnt--,_head->in(i));
// Peel off PhiNode edges as well
for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
Node *oj = _head->fast_out(j);
if( oj->is_Phi() ) {
PhiNode* old_phi = oj->as_Phi();
assert( old_phi->region() == _head, "" );
igvn.hash_delete(old_phi); // Yank from hash before hacking edges
Node *p = PhiNode::make_blank(landing_pad, old_phi);
uint icnt = fall_in_cnt;
for( i = oreq-1; i>0; i-- ) {
if( !phase->is_member( this, _head->in(i) ) ) {
p->init_req(icnt--, old_phi->in(i));
// Go ahead and clean out old edges from old phi
old_phi->del_req(i);
}
}
// Search for CSE's here, because ZKM.jar does a lot of
// loop hackery and we need to be a little incremental
// with the CSE to avoid O(N^2) node blow-up.
Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
if( p2 ) { // Found CSE
p->destruct(); // Recover useless new node
p = p2; // Use old node
} else {
igvn.register_new_node_with_optimizer(p, old_phi);
}
// Make old Phi refer to new Phi.
old_phi->add_req(p);
// Check for the special case of making the old phi useless and
// disappear it. In JavaGrande I have a case where this useless
// Phi is the loop limit and prevents recognizing a CountedLoop
// which in turn prevents removing an empty loop.
Node *id_old_phi = old_phi->Identity( &igvn );
if( id_old_phi != old_phi ) { // Found a simple identity?
// Note that I cannot call 'replace_node' here, because
// that will yank the edge from old_phi to the Region and
// I'm mid-iteration over the Region's uses.
for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
Node* use = old_phi->last_out(i);
igvn.rehash_node_delayed(use);
uint uses_found = 0;
for (uint j = 0; j < use->len(); j++) {
if (use->in(j) == old_phi) {
if (j < use->req()) use->set_req (j, id_old_phi);
else use->set_prec(j, id_old_phi);
uses_found++;
}
}
i -= uses_found; // we deleted 1 or more copies of this edge
}
}
igvn._worklist.push(old_phi);
}
}
// Finally clean out the fall-in edges from the RegionNode
for( i = oreq-1; i>0; i-- ) {
if( !phase->is_member( this, _head->in(i) ) ) {
_head->del_req(i);
}
}
// Transform landing pad
igvn.register_new_node_with_optimizer(landing_pad, _head);
// Insert landing pad into the header
_head->add_req(landing_pad);
}
//------------------------------split_outer_loop-------------------------------
// Split out the outermost loop from this shared header.
void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
PhaseIterGVN &igvn = phase->_igvn;
// Find index of outermost loop; it should also be my tail.
uint outer_idx = 1;
while( _head->in(outer_idx) != _tail ) outer_idx++;
// Make a LoopNode for the outermost loop.
Node *ctl = _head->in(LoopNode::EntryControl);
Node *outer = new (phase->C) LoopNode( ctl, _head->in(outer_idx) );
outer = igvn.register_new_node_with_optimizer(outer, _head);
phase->set_created_loop_node();
// Outermost loop falls into '_head' loop
_head->set_req(LoopNode::EntryControl, outer);
_head->del_req(outer_idx);
// Split all the Phis up between '_head' loop and 'outer' loop.
for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
Node *out = _head->fast_out(j);
if( out->is_Phi() ) {
PhiNode *old_phi = out->as_Phi();
assert( old_phi->region() == _head, "" );
Node *phi = PhiNode::make_blank(outer, old_phi);
phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl));
phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
phi = igvn.register_new_node_with_optimizer(phi, old_phi);
// Make old Phi point to new Phi on the fall-in path
igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
old_phi->del_req(outer_idx);
}
}
// Use the new loop head instead of the old shared one
_head = outer;
phase->set_loop(_head, this);
}
//------------------------------fix_parent-------------------------------------
static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
loop->_parent = parent;
if( loop->_child ) fix_parent( loop->_child, loop );
if( loop->_next ) fix_parent( loop->_next , parent );
}
//------------------------------estimate_path_freq-----------------------------
static float estimate_path_freq( Node *n ) {
// Try to extract some path frequency info
IfNode *iff;
for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
uint nop = n->Opcode();
if( nop == Op_SafePoint ) { // Skip any safepoint
n = n->in(0);
continue;
}
if( nop == Op_CatchProj ) { // Get count from a prior call
// Assume call does not always throw exceptions: means the call-site
// count is also the frequency of the fall-through path.
assert( n->is_CatchProj(), "" );
if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
return 0.0f; // Assume call exception path is rare
Node *call = n->in(0)->in(0)->in(0);
assert( call->is_Call(), "expect a call here" );
const JVMState *jvms = ((CallNode*)call)->jvms();
ciMethodData* methodData = jvms->method()->method_data();
if (!methodData->is_mature()) return 0.0f; // No call-site data
ciProfileData* data = methodData->bci_to_data(jvms->bci());
if ((data == NULL) || !data->is_CounterData()) {
// no call profile available, try call's control input
n = n->in(0);
continue;
}
return data->as_CounterData()->count()/FreqCountInvocations;
}
// See if there's a gating IF test
Node *n_c = n->in(0);
if( !n_c->is_If() ) break; // No estimate available
iff = n_c->as_If();
if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count?
// Compute how much count comes on this path
return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
// Have no count info. Skip dull uncommon-trap like branches.
if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) ||
(nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
break;
// Skip through never-taken branch; look for a real loop exit.
n = iff->in(0);
}
return 0.0f; // No estimate available
}
//------------------------------merge_many_backedges---------------------------
// Merge all the backedges from the shared header into a private Region.
// Feed that region as the one backedge to this loop.
void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
uint i;
// Scan for the top 2 hottest backedges
float hotcnt = 0.0f;
float warmcnt = 0.0f;
uint hot_idx = 0;
// Loop starts at 2 because slot 1 is the fall-in path
for( i = 2; i < _head->req(); i++ ) {
float cnt = estimate_path_freq(_head->in(i));
if( cnt > hotcnt ) { // Grab hottest path
warmcnt = hotcnt;
hotcnt = cnt;
hot_idx = i;
} else if( cnt > warmcnt ) { // And 2nd hottest path
warmcnt = cnt;
}
}
// See if the hottest backedge is worthy of being an inner loop
// by being much hotter than the next hottest backedge.
if( hotcnt <= 0.0001 ||
hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
// Peel out the backedges into a private merge point; peel
// them all except optionally hot_idx.
PhaseIterGVN &igvn = phase->_igvn;
Node *hot_tail = NULL;
// Make a Region for the merge point
Node *r = new (phase->C) RegionNode(1);
for( i = 2; i < _head->req(); i++ ) {
if( i != hot_idx )
r->add_req( _head->in(i) );
else hot_tail = _head->in(i);
}
igvn.register_new_node_with_optimizer(r, _head);
// Plug region into end of loop _head, followed by hot_tail
while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
_head->set_req(2, r);
if( hot_idx ) _head->add_req(hot_tail);
// Split all the Phis up between '_head' loop and the Region 'r'
for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
Node *out = _head->fast_out(j);
if( out->is_Phi() ) {
PhiNode* n = out->as_Phi();
igvn.hash_delete(n); // Delete from hash before hacking edges
Node *hot_phi = NULL;
Node *phi = new (phase->C) PhiNode(r, n->type(), n->adr_type());
// Check all inputs for the ones to peel out
uint j = 1;
for( uint i = 2; i < n->req(); i++ ) {
if( i != hot_idx )
phi->set_req( j++, n->in(i) );
else hot_phi = n->in(i);
}
// Register the phi but do not transform until whole place transforms
igvn.register_new_node_with_optimizer(phi, n);
// Add the merge phi to the old Phi
while( n->req() > 3 ) n->del_req( n->req()-1 );
n->set_req(2, phi);
if( hot_idx ) n->add_req(hot_phi);
}
}
// Insert a new IdealLoopTree inserted below me. Turn it into a clone
// of self loop tree. Turn self into a loop headed by _head and with
// tail being the new merge point.
IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
phase->set_loop(_tail,ilt); // Adjust tail
_tail = r; // Self's tail is new merge point
phase->set_loop(r,this);
ilt->_child = _child; // New guy has my children
_child = ilt; // Self has new guy as only child
ilt->_parent = this; // new guy has self for parent
ilt->_nest = _nest; // Same nesting depth (for now)
// Starting with 'ilt', look for child loop trees using the same shared
// header. Flatten these out; they will no longer be loops in the end.
IdealLoopTree **pilt = &_child;
while( ilt ) {
if( ilt->_head == _head ) {
uint i;
for( i = 2; i < _head->req(); i++ )
if( _head->in(i) == ilt->_tail )
break; // Still a loop
if( i == _head->req() ) { // No longer a loop
// Flatten ilt. Hang ilt's "_next" list from the end of
// ilt's '_child' list. Move the ilt's _child up to replace ilt.
IdealLoopTree **cp = &ilt->_child;
while( *cp ) cp = &(*cp)->_next; // Find end of child list
*cp = ilt->_next; // Hang next list at end of child list
*pilt = ilt->_child; // Move child up to replace ilt
ilt->_head = NULL; // Flag as a loop UNIONED into parent
ilt = ilt->_child; // Repeat using new ilt
continue; // do not advance over ilt->_child
}
assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
phase->set_loop(_head,ilt);
}
pilt = &ilt->_child; // Advance to next
ilt = *pilt;
}
if( _child ) fix_parent( _child, this );
}
//------------------------------beautify_loops---------------------------------
// Split shared headers and insert loop landing pads.
// Insert a LoopNode to replace the RegionNode.
// Return TRUE if loop tree is structurally changed.
bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
bool result = false;
// Cache parts in locals for easy
PhaseIterGVN &igvn = phase->_igvn;
igvn.hash_delete(_head); // Yank from hash before hacking edges
// Check for multiple fall-in paths. Peel off a landing pad if need be.
int fall_in_cnt = 0;
for( uint i = 1; i < _head->req(); i++ )
if( !phase->is_member( this, _head->in(i) ) )
fall_in_cnt++;
assert( fall_in_cnt, "at least 1 fall-in path" );
if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins
split_fall_in( phase, fall_in_cnt );
// Swap inputs to the _head and all Phis to move the fall-in edge to
// the left.
fall_in_cnt = 1;
while( phase->is_member( this, _head->in(fall_in_cnt) ) )
fall_in_cnt++;
if( fall_in_cnt > 1 ) {
// Since I am just swapping inputs I do not need to update def-use info
Node *tmp = _head->in(1);
_head->set_req( 1, _head->in(fall_in_cnt) );
_head->set_req( fall_in_cnt, tmp );
// Swap also all Phis
for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
Node* phi = _head->fast_out(i);
if( phi->is_Phi() ) {
igvn.hash_delete(phi); // Yank from hash before hacking edges
tmp = phi->in(1);
phi->set_req( 1, phi->in(fall_in_cnt) );
phi->set_req( fall_in_cnt, tmp );
}
}
}
assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
assert( phase->is_member( this, _head->in(2) ), "right edge is loop" );
// If I am a shared header (multiple backedges), peel off the many
// backedges into a private merge point and use the merge point as
// the one true backedge.
if( _head->req() > 3 ) {
// Merge the many backedges into a single backedge but leave
// the hottest backedge as separate edge for the following peel.
merge_many_backedges( phase );
result = true;
}
// If I have one hot backedge, peel off myself loop.
// I better be the outermost loop.
if( _head->req() > 3 ) {
split_outer_loop( phase );
result = true;
} else if( !_head->is_Loop() && !_irreducible ) {
// Make a new LoopNode to replace the old loop head
Node *l = new (phase->C) LoopNode( _head->in(1), _head->in(2) );
l = igvn.register_new_node_with_optimizer(l, _head);
phase->set_created_loop_node();
// Go ahead and replace _head
phase->_igvn.replace_node( _head, l );
_head = l;
phase->set_loop(_head, this);
}
// Now recursively beautify nested loops
if( _child ) result |= _child->beautify_loops( phase );
if( _next ) result |= _next ->beautify_loops( phase );
return result;
}
//------------------------------allpaths_check_safepts----------------------------
// Allpaths backwards scan from loop tail, terminating each path at first safepoint
// encountered. Helper for check_safepts.
void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
assert(stack.size() == 0, "empty stack");
stack.push(_tail);
visited.Clear();
visited.set(_tail->_idx);
while (stack.size() > 0) {
Node* n = stack.pop();
if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
// Terminate this path
} else if (n->Opcode() == Op_SafePoint) {
if (_phase->get_loop(n) != this) {
if (_required_safept == NULL) _required_safept = new Node_List();
_required_safept->push(n); // save the one closest to the tail
}
// Terminate this path
} else {
uint start = n->is_Region() ? 1 : 0;
uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
for (uint i = start; i < end; i++) {
Node* in = n->in(i);
assert(in->is_CFG(), "must be");
if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
stack.push(in);
}
}
}
}
}
//------------------------------check_safepts----------------------------
// Given dominators, try to find loops with calls that must always be
// executed (call dominates loop tail). These loops do not need non-call
// safepoints (ncsfpt).
//
// A complication is that a safepoint in a inner loop may be needed
// by an outer loop. In the following, the inner loop sees it has a
// call (block 3) on every path from the head (block 2) to the
// backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint)
// in block 2, _but_ this leaves the outer loop without a safepoint.
//
// entry 0
// |
// v
// outer 1,2 +->1
// | |
// | v
// | 2<---+ ncsfpt in 2
// |_/|\ |
// | v |
// inner 2,3 / 3 | call in 3
// / | |
// v +--+
// exit 4
//
//
// This method creates a list (_required_safept) of ncsfpt nodes that must
// be protected is created for each loop. When a ncsfpt maybe deleted, it
// is first looked for in the lists for the outer loops of the current loop.
//
// The insights into the problem:
// A) counted loops are okay
// B) innermost loops are okay (only an inner loop can delete
// a ncsfpt needed by an outer loop)
// C) a loop is immune from an inner loop deleting a safepoint
// if the loop has a call on the idom-path
// D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
// idom-path that is not in a nested loop
// E) otherwise, an ncsfpt on the idom-path that is nested in an inner
// loop needs to be prevented from deletion by an inner loop
//
// There are two analyses:
// 1) The first, and cheaper one, scans the loop body from
// tail to head following the idom (immediate dominator)
// chain, looking for the cases (C,D,E) above.
// Since inner loops are scanned before outer loops, there is summary
// information about inner loops. Inner loops can be skipped over
// when the tail of an inner loop is encountered.
//
// 2) The second, invoked if the first fails to find a call or ncsfpt on
// the idom path (which is rare), scans all predecessor control paths
// from the tail to the head, terminating a path when a call or sfpt
// is encountered, to find the ncsfpt's that are closest to the tail.
//
void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
// Bottom up traversal
IdealLoopTree* ch = _child;
if (_child) _child->check_safepts(visited, stack);
if (_next) _next ->check_safepts(visited, stack);
if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
bool has_call = false; // call on dom-path
bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth
// Scan the dom-path nodes from tail to head
for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
has_call = true;
_has_sfpt = 1; // Then no need for a safept!
break;
} else if (n->Opcode() == Op_SafePoint) {
if (_phase->get_loop(n) == this) {
has_local_ncsfpt = true;
break;
}
if (nonlocal_ncsfpt == NULL) {
nonlocal_ncsfpt = n; // save the one closest to the tail
}
} else {
IdealLoopTree* nlpt = _phase->get_loop(n);
if (this != nlpt) {
// If at an inner loop tail, see if the inner loop has already
// recorded seeing a call on the dom-path (and stop.) If not,
// jump to the head of the inner loop.
assert(is_member(nlpt), "nested loop");
Node* tail = nlpt->_tail;
if (tail->in(0)->is_If()) tail = tail->in(0);
if (n == tail) {
// If inner loop has call on dom-path, so does outer loop
if (nlpt->_has_sfpt) {
has_call = true;
_has_sfpt = 1;
break;
}
// Skip to head of inner loop
assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
n = nlpt->_head;
}
}
}
}
// Record safept's that this loop needs preserved when an
// inner loop attempts to delete it's safepoints.
if (_child != NULL && !has_call && !has_local_ncsfpt) {
if (nonlocal_ncsfpt != NULL) {
if (_required_safept == NULL) _required_safept = new Node_List();
_required_safept->push(nonlocal_ncsfpt);
} else {
// Failed to find a suitable safept on the dom-path. Now use
// an all paths walk from tail to head, looking for safepoints to preserve.
allpaths_check_safepts(visited, stack);
}
}
}
}
//---------------------------is_deleteable_safept----------------------------
// Is safept not required by an outer loop?
bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
assert(sfpt->Opcode() == Op_SafePoint, "");
IdealLoopTree* lp = get_loop(sfpt)->_parent;
while (lp != NULL) {
Node_List* sfpts = lp->_required_safept;
if (sfpts != NULL) {
for (uint i = 0; i < sfpts->size(); i++) {
if (sfpt == sfpts->at(i))
return false;
}
}
lp = lp->_parent;
}
return true;
}
//---------------------------replace_parallel_iv-------------------------------
// Replace parallel induction variable (parallel to trip counter)
void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
assert(loop->_head->is_CountedLoop(), "");
CountedLoopNode *cl = loop->_head->as_CountedLoop();
if (!cl->is_valid_counted_loop())
return; // skip malformed counted loop
Node *incr = cl->incr();
if (incr == NULL)
return; // Dead loop?
Node *init = cl->init_trip();
Node *phi = cl->phi();
int stride_con = cl->stride_con();
// Visit all children, looking for Phis
for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
Node *out = cl->out(i);
// Look for other phis (secondary IVs). Skip dead ones
if (!out->is_Phi() || out == phi || !has_node(out))
continue;
PhiNode* phi2 = out->as_Phi();
Node *incr2 = phi2->in( LoopNode::LoopBackControl );
// Look for induction variables of the form: X += constant
if (phi2->region() != loop->_head ||
incr2->req() != 3 ||
incr2->in(1) != phi2 ||
incr2 == incr ||
incr2->Opcode() != Op_AddI ||
!incr2->in(2)->is_Con())
continue;
// Check for parallel induction variable (parallel to trip counter)
// via an affine function. In particular, count-down loops with
// count-up array indices are common. We only RCE references off
// the trip-counter, so we need to convert all these to trip-counter
// expressions.
Node *init2 = phi2->in( LoopNode::EntryControl );
int stride_con2 = incr2->in(2)->get_int();
// The general case here gets a little tricky. We want to find the
// GCD of all possible parallel IV's and make a new IV using this
// GCD for the loop. Then all possible IVs are simple multiples of
// the GCD. In practice, this will cover very few extra loops.
// Instead we require 'stride_con2' to be a multiple of 'stride_con',
// where +/-1 is the common case, but other integer multiples are
// also easy to handle.
int ratio_con = stride_con2/stride_con;
if ((ratio_con * stride_con) == stride_con2) { // Check for exact
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print("Parallel IV: %d ", phi2->_idx);
loop->dump_head();
}
#endif
// Convert to using the trip counter. The parallel induction
// variable differs from the trip counter by a loop-invariant
// amount, the difference between their respective initial values.
// It is scaled by the 'ratio_con'.
Node* ratio = _igvn.intcon(ratio_con);
set_ctrl(ratio, C->root());
Node* ratio_init = new (C) MulINode(init, ratio);
_igvn.register_new_node_with_optimizer(ratio_init, init);
set_early_ctrl(ratio_init);
Node* diff = new (C) SubINode(init2, ratio_init);
_igvn.register_new_node_with_optimizer(diff, init2);
set_early_ctrl(diff);
Node* ratio_idx = new (C) MulINode(phi, ratio);
_igvn.register_new_node_with_optimizer(ratio_idx, phi);
set_ctrl(ratio_idx, cl);
Node* add = new (C) AddINode(ratio_idx, diff);
_igvn.register_new_node_with_optimizer(add);
set_ctrl(add, cl);
_igvn.replace_node( phi2, add );
// Sometimes an induction variable is unused
if (add->outcnt() == 0) {
_igvn.remove_dead_node(add);
}
--i; // deleted this phi; rescan starting with next position
continue;
}
}
}
//------------------------------counted_loop-----------------------------------
// Convert to counted loops where possible
void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
// For grins, set the inner-loop flag here
if (!_child) {
if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
}
if (_head->is_CountedLoop() ||
phase->is_counted_loop(_head, this)) {
_has_sfpt = 1; // Indicate we do not need a safepoint here
// Look for safepoints to remove.
Node_List* sfpts = _safepts;
if (sfpts != NULL) {
for (uint i = 0; i < sfpts->size(); i++) {
Node* n = sfpts->at(i);
assert(phase->get_loop(n) == this, "");
if (phase->is_deleteable_safept(n)) {
phase->lazy_replace(n, n->in(TypeFunc::Control));
}
}
}
// Look for induction variables
phase->replace_parallel_iv(this);
} else if (_parent != NULL && !_irreducible) {
// Not a counted loop.
// Look for a safepoint on the idom-path.
Node* sfpt = tail();
for (; sfpt != _head; sfpt = phase->idom(sfpt)) {
if (sfpt->Opcode() == Op_SafePoint && phase->get_loop(sfpt) == this)
break; // Found one
}
// Delete other safepoints in this loop.
Node_List* sfpts = _safepts;
if (sfpts != NULL && sfpt != _head && sfpt->Opcode() == Op_SafePoint) {
for (uint i = 0; i < sfpts->size(); i++) {
Node* n = sfpts->at(i);
assert(phase->get_loop(n) == this, "");
if (n != sfpt && phase->is_deleteable_safept(n)) {
phase->lazy_replace(n, n->in(TypeFunc::Control));
}
}
}
}
// Recursively
if (_child) _child->counted_loop( phase );
if (_next) _next ->counted_loop( phase );
}
#ifndef PRODUCT
//------------------------------dump_head--------------------------------------
// Dump 1 liner for loop header info
void IdealLoopTree::dump_head( ) const {
for (uint i=0; i<_nest; i++)
tty->print(" ");
tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
if (_irreducible) tty->print(" IRREDUCIBLE");
Node* entry = _head->in(LoopNode::EntryControl);
if (LoopLimitCheck) {
Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
if (predicate != NULL ) {
tty->print(" limit_check");
entry = entry->in(0)->in(0);
}
}
if (UseLoopPredicate) {
entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
if (entry != NULL) {
tty->print(" predicated");
}
}
if (_head->is_CountedLoop()) {
CountedLoopNode *cl = _head->as_CountedLoop();
tty->print(" counted");
Node* init_n = cl->init_trip();
if (init_n != NULL && init_n->is_Con())
tty->print(" [%d,", cl->init_trip()->get_int());
else
tty->print(" [int,");
Node* limit_n = cl->limit();
if (limit_n != NULL && limit_n->is_Con())
tty->print("%d),", cl->limit()->get_int());
else
tty->print("int),");
int stride_con = cl->stride_con();
if (stride_con > 0) tty->print("+");
tty->print("%d", stride_con);
tty->print(" (%d iters) ", (int)cl->profile_trip_cnt());
if (cl->is_pre_loop ()) tty->print(" pre" );
if (cl->is_main_loop()) tty->print(" main");
if (cl->is_post_loop()) tty->print(" post");
}
tty->cr();
}
//------------------------------dump-------------------------------------------
// Dump loops by loop tree
void IdealLoopTree::dump( ) const {
dump_head();
if (_child) _child->dump();
if (_next) _next ->dump();
}
#endif
static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
if (loop == root) {
if (loop->_child != NULL) {
log->begin_head("loop_tree");
log->end_head();
if( loop->_child ) log_loop_tree(root, loop->_child, log);
log->tail("loop_tree");
assert(loop->_next == NULL, "what?");
}
} else {
Node* head = loop->_head;
log->begin_head("loop");
log->print(" idx='%d' ", head->_idx);
if (loop->_irreducible) log->print("irreducible='1' ");
if (head->is_Loop()) {
if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
}
if (head->is_CountedLoop()) {
CountedLoopNode* cl = head->as_CountedLoop();
if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx());
if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
}
log->end_head();
if( loop->_child ) log_loop_tree(root, loop->_child, log);
log->tail("loop");
if( loop->_next ) log_loop_tree(root, loop->_next, log);
}
}
//---------------------collect_potentially_useful_predicates-----------------------
// Helper function to collect potentially useful predicates to prevent them from
// being eliminated by PhaseIdealLoop::eliminate_useless_predicates
void PhaseIdealLoop::collect_potentially_useful_predicates(
IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
if (loop->_child) { // child
collect_potentially_useful_predicates(loop->_child, useful_predicates);
}
// self (only loops that we can apply loop predication may use their predicates)
if (loop->_head->is_Loop() &&
!loop->_irreducible &&
!loop->tail()->is_top()) {
LoopNode* lpn = loop->_head->as_Loop();
Node* entry = lpn->in(LoopNode::EntryControl);
Node* predicate_proj = find_predicate(entry); // loop_limit_check first
if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
entry = entry->in(0)->in(0);
}
predicate_proj = find_predicate(entry); // Predicate
if (predicate_proj != NULL ) {
useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
}
}
if (loop->_next) { // sibling
collect_potentially_useful_predicates(loop->_next, useful_predicates);
}
}
//------------------------eliminate_useless_predicates-----------------------------
// Eliminate all inserted predicates if they could not be used by loop predication.
// Note: it will also eliminates loop limits check predicate since it also uses
// Opaque1 node (see Parse::add_predicate()).
void PhaseIdealLoop::eliminate_useless_predicates() {
if (C->predicate_count() == 0)
return; // no predicate left
Unique_Node_List useful_predicates; // to store useful predicates
if (C->has_loops()) {
collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
}
for (int i = C->predicate_count(); i > 0; i--) {
Node * n = C->predicate_opaque1_node(i-1);
assert(n->Opcode() == Op_Opaque1, "must be");
if (!useful_predicates.member(n)) { // not in the useful list
_igvn.replace_node(n, n->in(1));
}
}
}
//------------------------process_expensive_nodes-----------------------------
// Expensive nodes have their control input set to prevent the GVN
// from commoning them and as a result forcing the resulting node to
// be in a more frequent path. Use CFG information here, to change the
// control inputs so that some expensive nodes can be commoned while
// not executed more frequently.
bool PhaseIdealLoop::process_expensive_nodes() {
assert(OptimizeExpensiveOps, "optimization off?");
// Sort nodes to bring similar nodes together
C->sort_expensive_nodes();
bool progress = false;
for (int i = 0; i < C->expensive_count(); ) {
Node* n = C->expensive_node(i);
int start = i;
// Find nodes similar to n
i++;
for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
int end = i;
// And compare them two by two
for (int j = start; j < end; j++) {
Node* n1 = C->expensive_node(j);
if (is_node_unreachable(n1)) {
continue;
}
for (int k = j+1; k < end; k++) {
Node* n2 = C->expensive_node(k);
if (is_node_unreachable(n2)) {
continue;
}
assert(n1 != n2, "should be pair of nodes");
Node* c1 = n1->in(0);
Node* c2 = n2->in(0);
Node* parent_c1 = c1;
Node* parent_c2 = c2;
// The call to get_early_ctrl_for_expensive() moves the
// expensive nodes up but stops at loops that are in a if
// branch. See whether we can exit the loop and move above the
// If.
if (c1->is_Loop()) {
parent_c1 = c1->in(1);
}
if (c2->is_Loop()) {
parent_c2 = c2->in(1);
}
if (parent_c1 == parent_c2) {
_igvn._worklist.push(n1);
_igvn._worklist.push(n2);
continue;
}
// Look for identical expensive node up the dominator chain.
if (is_dominator(c1, c2)) {
c2 = c1;
} else if (is_dominator(c2, c1)) {
c1 = c2;
} else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
// Both branches have the same expensive node so move it up
// before the if.
c1 = c2 = idom(parent_c1->in(0));
}
// Do the actual moves
if (n1->in(0) != c1) {
_igvn.hash_delete(n1);
n1->set_req(0, c1);
_igvn.hash_insert(n1);
_igvn._worklist.push(n1);
progress = true;
}
if (n2->in(0) != c2) {
_igvn.hash_delete(n2);
n2->set_req(0, c2);
_igvn.hash_insert(n2);
_igvn._worklist.push(n2);
progress = true;
}
}
}
}
return progress;
}
//=============================================================================
//----------------------------build_and_optimize-------------------------------
// Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to
// its corresponding LoopNode. If 'optimize' is true, do some loop cleanups.
void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool skip_loop_opts) {
ResourceMark rm;
int old_progress = C->major_progress();
uint orig_worklist_size = _igvn._worklist.size();
// Reset major-progress flag for the driver's heuristics
C->clear_major_progress();
#ifndef PRODUCT
// Capture for later assert
uint unique = C->unique();
_loop_invokes++;
_loop_work += unique;
#endif
// True if the method has at least 1 irreducible loop
_has_irreducible_loops = false;
_created_loop_node = false;
Arena *a = Thread::current()->resource_area();
VectorSet visited(a);
// Pre-grow the mapping from Nodes to IdealLoopTrees.
_nodes.map(C->unique(), NULL);
memset(_nodes.adr(), 0, wordSize * C->unique());
// Pre-build the top-level outermost loop tree entry
_ltree_root = new IdealLoopTree( this, C->root(), C->root() );
// Do not need a safepoint at the top level
_ltree_root->_has_sfpt = 1;
// Initialize Dominators.
// Checked in clone_loop_predicate() during beautify_loops().
_idom_size = 0;
_idom = NULL;
_dom_depth = NULL;
_dom_stk = NULL;
// Empty pre-order array
allocate_preorders();
// Build a loop tree on the fly. Build a mapping from CFG nodes to
// IdealLoopTree entries. Data nodes are NOT walked.
build_loop_tree();
// Check for bailout, and return
if (C->failing()) {
return;
}
// No loops after all
if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
// There should always be an outer loop containing the Root and Return nodes.
// If not, we have a degenerate empty program. Bail out in this case.
if (!has_node(C->root())) {
if (!_verify_only) {
C->clear_major_progress();
C->record_method_not_compilable("empty program detected during loop optimization");
}
return;
}
// Nothing to do, so get out
bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only;
bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
if (stop_early && !do_expensive_nodes) {
_igvn.optimize(); // Cleanup NeverBranches
return;
}
// Set loop nesting depth
_ltree_root->set_nest( 0 );
// Split shared headers and insert loop landing pads.
// Do not bother doing this on the Root loop of course.
if( !_verify_me && !_verify_only && _ltree_root->_child ) {
C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
if( _ltree_root->_child->beautify_loops( this ) ) {
// Re-build loop tree!
_ltree_root->_child = NULL;
_nodes.clear();
reallocate_preorders();
build_loop_tree();
// Check for bailout, and return
if (C->failing()) {
return;
}
// Reset loop nesting depth
_ltree_root->set_nest( 0 );
C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
}
}
// Build Dominators for elision of NULL checks & loop finding.
// Since nodes do not have a slot for immediate dominator, make
// a persistent side array for that info indexed on node->_idx.
_idom_size = C->unique();
_idom = NEW_RESOURCE_ARRAY( Node*, _idom_size );
_dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size );
_dom_stk = NULL; // Allocated on demand in recompute_dom_depth
memset( _dom_depth, 0, _idom_size * sizeof(uint) );
Dominators();
if (!_verify_only) {
// As a side effect, Dominators removed any unreachable CFG paths
// into RegionNodes. It doesn't do this test against Root, so
// we do it here.
for( uint i = 1; i < C->root()->req(); i++ ) {
if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root?
_igvn.delete_input_of(C->root(), i);
i--; // Rerun same iteration on compressed edges
}
}
// Given dominators, try to find inner loops with calls that must
// always be executed (call dominates loop tail). These loops do
// not need a separate safepoint.
Node_List cisstack(a);
_ltree_root->check_safepts(visited, cisstack);
}
// Walk the DATA nodes and place into loops. Find earliest control
// node. For CFG nodes, the _nodes array starts out and remains
// holding the associated IdealLoopTree pointer. For DATA nodes, the
// _nodes array holds the earliest legal controlling CFG node.
// Allocate stack with enough space to avoid frequent realloc
int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats
Node_Stack nstack( a, stack_size );
visited.Clear();
Node_List worklist(a);
// Don't need C->root() on worklist since
// it will be processed among C->top() inputs
worklist.push( C->top() );
visited.set( C->top()->_idx ); // Set C->top() as visited now
build_loop_early( visited, worklist, nstack );
// Given early legal placement, try finding counted loops. This placement
// is good enough to discover most loop invariants.
if( !_verify_me && !_verify_only )
_ltree_root->counted_loop( this );
// Find latest loop placement. Find ideal loop placement.
visited.Clear();
init_dom_lca_tags();
// Need C->root() on worklist when processing outs
worklist.push( C->root() );
NOT_PRODUCT( C->verify_graph_edges(); )
worklist.push( C->top() );
build_loop_late( visited, worklist, nstack );
if (_verify_only) {
// restore major progress flag
for (int i = 0; i < old_progress; i++)
C->set_major_progress();
assert(C->unique() == unique, "verification mode made Nodes? ? ?");
assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
return;
}
// clear out the dead code after build_loop_late
while (_deadlist.size()) {
_igvn.remove_globally_dead_node(_deadlist.pop());
}
if (stop_early) {
assert(do_expensive_nodes, "why are we here?");
if (process_expensive_nodes()) {
// If we made some progress when processing expensive nodes then
// the IGVN may modify the graph in a way that will allow us to
// make some more progress: we need to try processing expensive
// nodes again.
C->set_major_progress();
}
_igvn.optimize();
return;
}
// Some parser-inserted loop predicates could never be used by loop
// predication or they were moved away from loop during some optimizations.
// For example, peeling. Eliminate them before next loop optimizations.
if (UseLoopPredicate || LoopLimitCheck) {
eliminate_useless_predicates();
}
#ifndef PRODUCT
C->verify_graph_edges();
if (_verify_me) { // Nested verify pass?
// Check to see if the verify mode is broken
assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
return;
}
if(VerifyLoopOptimizations) verify();
if(TraceLoopOpts && C->has_loops()) {
_ltree_root->dump();
}
#endif
if (skip_loop_opts) {
// Cleanup any modified bits
_igvn.optimize();
if (C->log() != NULL) {
log_loop_tree(_ltree_root, _ltree_root, C->log());
}
return;
}
if (ReassociateInvariants) {
// Reassociate invariants and prep for split_thru_phi
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (!lpt->is_counted() || !lpt->is_inner()) continue;
lpt->reassociate_invariants(this);
// Because RCE opportunities can be masked by split_thru_phi,
// look for RCE candidates and inhibit split_thru_phi
// on just their loop-phi's for this pass of loop opts
if (SplitIfBlocks && do_split_ifs) {
if (lpt->policy_range_check(this)) {
lpt->_rce_candidate = 1; // = true
}
}
}
}
// Check for aggressive application of split-if and other transforms
// that require basic-block info (like cloning through Phi's)
if( SplitIfBlocks && do_split_ifs ) {
visited.Clear();
split_if_with_blocks( visited, nstack );
NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
}
if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
C->set_major_progress();
}
// Perform loop predication before iteration splitting
if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
_ltree_root->_child->loop_predication(this);
}
if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
if (do_intrinsify_fill()) {
C->set_major_progress();
}
}
// Perform iteration-splitting on inner loops. Split iterations to avoid
// range checks or one-shot null checks.
// If split-if's didn't hack the graph too bad (no CFG changes)
// then do loop opts.
if (C->has_loops() && !C->major_progress()) {
memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
_ltree_root->_child->iteration_split( this, worklist );
// No verify after peeling! GCM has hoisted code out of the loop.
// After peeling, the hoisted code could sink inside the peeled area.
// The peeling code does not try to recompute the best location for
// all the code before the peeled area, so the verify pass will always
// complain about it.
}
// Do verify graph edges in any case
NOT_PRODUCT( C->verify_graph_edges(); );
if (!do_split_ifs) {
// We saw major progress in Split-If to get here. We forced a
// pass with unrolling and not split-if, however more split-if's
// might make progress. If the unrolling didn't make progress
// then the major-progress flag got cleared and we won't try
// another round of Split-If. In particular the ever-common
// instance-of/check-cast pattern requires at least 2 rounds of
// Split-If to clear out.
C->set_major_progress();
}
// Repeat loop optimizations if new loops were seen
if (created_loop_node()) {
C->set_major_progress();
}
// Keep loop predicates and perform optimizations with them
// until no more loop optimizations could be done.
// After that switch predicates off and do more loop optimizations.
if (!C->major_progress() && (C->predicate_count() > 0)) {
C->cleanup_loop_predicates(_igvn);
#ifndef PRODUCT
if (TraceLoopOpts) {
tty->print_cr("PredicatesOff");
}
#endif
C->set_major_progress();
}
// Convert scalar to superword operations at the end of all loop opts.
if (UseSuperWord && C->has_loops() && !C->major_progress()) {
// SuperWord transform
SuperWord sw(this);
for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
IdealLoopTree* lpt = iter.current();
if (lpt->is_counted()) {
sw.transform_loop(lpt);
}
}
}
// Cleanup any modified bits
_igvn.optimize();
// disable assert until issue with split_flow_path is resolved (6742111)
// assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
// "shouldn't introduce irreducible loops");
if (C->log() != NULL) {
log_loop_tree(_ltree_root, _ltree_root, C->log());
}
}
#ifndef PRODUCT
//------------------------------print_statistics-------------------------------
int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
void PhaseIdealLoop::print_statistics() {
tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
}
//------------------------------verify-----------------------------------------
// Build a verify-only PhaseIdealLoop, and see that it agrees with me.
static int fail; // debug only, so its multi-thread dont care
void PhaseIdealLoop::verify() const {
int old_progress = C->major_progress();
ResourceMark rm;
PhaseIdealLoop loop_verify( _igvn, this );
VectorSet visited(Thread::current()->resource_area());
fail = 0;
verify_compare( C->root(), &loop_verify, visited );
assert( fail == 0, "verify loops failed" );
// Verify loop structure is the same
_ltree_root->verify_tree(loop_verify._ltree_root, NULL);
// Reset major-progress. It was cleared by creating a verify version of
// PhaseIdealLoop.
for( int i=0; i<old_progress; i++ )
C->set_major_progress();
}
//------------------------------verify_compare---------------------------------
// Make sure me and the given PhaseIdealLoop agree on key data structures
void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
if( !n ) return;
if( visited.test_set( n->_idx ) ) return;
if( !_nodes[n->_idx] ) { // Unreachable
assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
return;
}
uint i;
for( i = 0; i < n->req(); i++ )
verify_compare( n->in(i), loop_verify, visited );
// Check the '_nodes' block/loop structure
i = n->_idx;
if( has_ctrl(n) ) { // We have control; verify has loop or ctrl
if( _nodes[i] != loop_verify->_nodes[i] &&
get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
tty->print("Mismatched control setting for: ");
n->dump();
if( fail++ > 10 ) return;
Node *c = get_ctrl_no_update(n);
tty->print("We have it as: ");
if( c->in(0) ) c->dump();
else tty->print_cr("N%d",c->_idx);
tty->print("Verify thinks: ");
if( loop_verify->has_ctrl(n) )
loop_verify->get_ctrl_no_update(n)->dump();
else
loop_verify->get_loop_idx(n)->dump();
tty->cr();
}
} else { // We have a loop
IdealLoopTree *us = get_loop_idx(n);
if( loop_verify->has_ctrl(n) ) {
tty->print("Mismatched loop setting for: ");
n->dump();
if( fail++ > 10 ) return;
tty->print("We have it as: ");
us->dump();
tty->print("Verify thinks: ");
loop_verify->get_ctrl_no_update(n)->dump();
tty->cr();
} else if (!C->major_progress()) {
// Loop selection can be messed up if we did a major progress
// operation, like split-if. Do not verify in that case.
IdealLoopTree *them = loop_verify->get_loop_idx(n);
if( us->_head != them->_head || us->_tail != them->_tail ) {
tty->print("Unequals loops for: ");
n->dump();
if( fail++ > 10 ) return;
tty->print("We have it as: ");
us->dump();
tty->print("Verify thinks: ");
them->dump();
tty->cr();
}
}
}
// Check for immediate dominators being equal
if( i >= _idom_size ) {
if( !n->is_CFG() ) return;
tty->print("CFG Node with no idom: ");
n->dump();
return;
}
if( !n->is_CFG() ) return;
if( n == C->root() ) return; // No IDOM here
assert(n->_idx == i, "sanity");
Node *id = idom_no_update(n);
if( id != loop_verify->idom_no_update(n) ) {
tty->print("Unequals idoms for: ");
n->dump();
if( fail++ > 10 ) return;
tty->print("We have it as: ");
id->dump();
tty->print("Verify thinks: ");
loop_verify->idom_no_update(n)->dump();
tty->cr();
}
}
//------------------------------verify_tree------------------------------------
// Verify that tree structures match. Because the CFG can change, siblings
// within the loop tree can be reordered. We attempt to deal with that by
// reordering the verify's loop tree if possible.
void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
assert( _parent == parent, "Badly formed loop tree" );
// Siblings not in same order? Attempt to re-order.
if( _head != loop->_head ) {
// Find _next pointer to update
IdealLoopTree **pp = &loop->_parent->_child;
while( *pp != loop )
pp = &((*pp)->_next);
// Find proper sibling to be next
IdealLoopTree **nn = &loop->_next;
while( (*nn) && (*nn)->_head != _head )
nn = &((*nn)->_next);
// Check for no match.
if( !(*nn) ) {
// Annoyingly, irreducible loops can pick different headers
// after a major_progress operation, so the rest of the loop
// tree cannot be matched.
if (_irreducible && Compile::current()->major_progress()) return;
assert( 0, "failed to match loop tree" );
}
// Move (*nn) to (*pp)
IdealLoopTree *hit = *nn;
*nn = hit->_next;
hit->_next = loop;
*pp = loop;
loop = hit;
// Now try again to verify
}
assert( _head == loop->_head , "mismatched loop head" );
Node *tail = _tail; // Inline a non-updating version of
while( !tail->in(0) ) // the 'tail()' call.
tail = tail->in(1);
assert( tail == loop->_tail, "mismatched loop tail" );
// Counted loops that are guarded should be able to find their guards
if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
CountedLoopNode *cl = _head->as_CountedLoop();
Node *init = cl->init_trip();
Node *ctrl = cl->in(LoopNode::EntryControl);
assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
Node *iff = ctrl->in(0);
assert( iff->Opcode() == Op_If, "" );
Node *bol = iff->in(1);
assert( bol->Opcode() == Op_Bool, "" );
Node *cmp = bol->in(1);
assert( cmp->Opcode() == Op_CmpI, "" );
Node *add = cmp->in(1);
Node *opaq;
if( add->Opcode() == Op_Opaque1 ) {
opaq = add;
} else {
assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
assert( add == init, "" );
opaq = cmp->in(2);
}
assert( opaq->Opcode() == Op_Opaque1, "" );
}
if (_child != NULL) _child->verify_tree(loop->_child, this);
if (_next != NULL) _next ->verify_tree(loop->_next, parent);
// Innermost loops need to verify loop bodies,
// but only if no 'major_progress'
int fail = 0;
if (!Compile::current()->major_progress() && _child == NULL) {
for( uint i = 0; i < _body.size(); i++ ) {
Node *n = _body.at(i);
if (n->outcnt() == 0) continue; // Ignore dead
uint j;
for( j = 0; j < loop->_body.size(); j++ )
if( loop->_body.at(j) == n )
break;
if( j == loop->_body.size() ) { // Not found in loop body
// Last ditch effort to avoid assertion: Its possible that we
// have some users (so outcnt not zero) but are still dead.
// Try to find from root.
if (Compile::current()->root()->find(n->_idx)) {
fail++;
tty->print("We have that verify does not: ");
n->dump();
}
}
}
for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
Node *n = loop->_body.at(i2);
if (n->outcnt() == 0) continue; // Ignore dead
uint j;
for( j = 0; j < _body.size(); j++ )
if( _body.at(j) == n )
break;
if( j == _body.size() ) { // Not found in loop body
// Last ditch effort to avoid assertion: Its possible that we
// have some users (so outcnt not zero) but are still dead.
// Try to find from root.
if (Compile::current()->root()->find(n->_idx)) {
fail++;
tty->print("Verify has that we do not: ");
n->dump();
}
}
}
assert( !fail, "loop body mismatch" );
}
}
#endif
//------------------------------set_idom---------------------------------------
void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
uint idx = d->_idx;
if (idx >= _idom_size) {
uint newsize = _idom_size<<1;
while( idx >= newsize ) {
newsize <<= 1;
}
_idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize);
_dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
_idom_size = newsize;
}
_idom[idx] = n;
_dom_depth[idx] = dom_depth;
}
//------------------------------recompute_dom_depth---------------------------------------
// The dominator tree is constructed with only parent pointers.
// This recomputes the depth in the tree by first tagging all
// nodes as "no depth yet" marker. The next pass then runs up
// the dom tree from each node marked "no depth yet", and computes
// the depth on the way back down.
void PhaseIdealLoop::recompute_dom_depth() {
uint no_depth_marker = C->unique();
uint i;
// Initialize depth to "no depth yet"
for (i = 0; i < _idom_size; i++) {
if (_dom_depth[i] > 0 && _idom[i] != NULL) {
_dom_depth[i] = no_depth_marker;
}
}
if (_dom_stk == NULL) {
uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size.
if (init_size < 10) init_size = 10;
_dom_stk = new GrowableArray<uint>(init_size);
}
// Compute new depth for each node.
for (i = 0; i < _idom_size; i++) {
uint j = i;
// Run up the dom tree to find a node with a depth
while (_dom_depth[j] == no_depth_marker) {
_dom_stk->push(j);
j = _idom[j]->_idx;
}
// Compute the depth on the way back down this tree branch
uint dd = _dom_depth[j] + 1;
while (_dom_stk->length() > 0) {
uint j = _dom_stk->pop();
_dom_depth[j] = dd;
dd++;
}
}
}
//------------------------------sort-------------------------------------------
// Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the
// loop tree, not the root.
IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
if( !innermost ) return loop; // New innermost loop
int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
assert( loop_preorder, "not yet post-walked loop" );
IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer
IdealLoopTree *l = *pp; // Do I go before or after 'l'?
// Insert at start of list
while( l ) { // Insertion sort based on pre-order
if( l == loop ) return innermost; // Already on list!
int l_preorder = get_preorder(l->_head); // Cache pre-order number
assert( l_preorder, "not yet post-walked l" );
// Check header pre-order number to figure proper nesting
if( loop_preorder > l_preorder )
break; // End of insertion
// If headers tie (e.g., shared headers) check tail pre-order numbers.
// Since I split shared headers, you'd think this could not happen.
// BUT: I must first do the preorder numbering before I can discover I
// have shared headers, so the split headers all get the same preorder
// number as the RegionNode they split from.
if( loop_preorder == l_preorder &&
get_preorder(loop->_tail) < get_preorder(l->_tail) )
break; // Also check for shared headers (same pre#)
pp = &l->_parent; // Chain up list
l = *pp;
}
// Link into list
// Point predecessor to me
*pp = loop;
// Point me to successor
IdealLoopTree *p = loop->_parent;
loop->_parent = l; // Point me to successor
if( p ) sort( p, innermost ); // Insert my parents into list as well
return innermost;
}
//------------------------------build_loop_tree--------------------------------
// I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit
// bits. The _nodes[] array is mapped by Node index and holds a NULL for
// not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
// tightest enclosing IdealLoopTree for post-walked.
//
// During my forward walk I do a short 1-layer lookahead to see if I can find
// a loop backedge with that doesn't have any work on the backedge. This
// helps me construct nested loops with shared headers better.
//
// Once I've done the forward recursion, I do the post-work. For each child
// I check to see if there is a backedge. Backedges define a loop! I
// insert an IdealLoopTree at the target of the backedge.
//
// During the post-work I also check to see if I have several children
// belonging to different loops. If so, then this Node is a decision point
// where control flow can choose to change loop nests. It is at this
// decision point where I can figure out how loops are nested. At this
// time I can properly order the different loop nests from my children.
// Note that there may not be any backedges at the decision point!
//
// Since the decision point can be far removed from the backedges, I can't
// order my loops at the time I discover them. Thus at the decision point
// I need to inspect loop header pre-order numbers to properly nest my
// loops. This means I need to sort my childrens' loops by pre-order.
// The sort is of size number-of-control-children, which generally limits
// it to size 2 (i.e., I just choose between my 2 target loops).
void PhaseIdealLoop::build_loop_tree() {
// Allocate stack of size C->unique()/2 to avoid frequent realloc
GrowableArray <Node *> bltstack(C->unique() >> 1);
Node *n = C->root();
bltstack.push(n);
int pre_order = 1;
int stack_size;
while ( ( stack_size = bltstack.length() ) != 0 ) {
n = bltstack.top(); // Leave node on stack
if ( !is_visited(n) ) {
// ---- Pre-pass Work ----
// Pre-walked but not post-walked nodes need a pre_order number.
set_preorder_visited( n, pre_order ); // set as visited
// ---- Scan over children ----
// Scan first over control projections that lead to loop headers.
// This helps us find inner-to-outer loops with shared headers better.
// Scan children's children for loop headers.
for ( int i = n->outcnt() - 1; i >= 0; --i ) {
Node* m = n->raw_out(i); // Child
if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
// Scan over children's children to find loop
for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
Node* l = m->fast_out(j);
if( is_visited(l) && // Been visited?
!is_postvisited(l) && // But not post-visited
get_preorder(l) < pre_order ) { // And smaller pre-order
// Found! Scan the DFS down this path before doing other paths
bltstack.push(m);
break;
}
}
}
}
pre_order++;
}
else if ( !is_postvisited(n) ) {
// Note: build_loop_tree_impl() adds out edges on rare occasions,
// such as com.sun.rsasign.am::a.
// For non-recursive version, first, process current children.
// On next iteration, check if additional children were added.
for ( int k = n->outcnt() - 1; k >= 0; --k ) {
Node* u = n->raw_out(k);
if ( u->is_CFG() && !is_visited(u) ) {
bltstack.push(u);
}
}
if ( bltstack.length() == stack_size ) {
// There were no additional children, post visit node now
(void)bltstack.pop(); // Remove node from stack
pre_order = build_loop_tree_impl( n, pre_order );
// Check for bailout
if (C->failing()) {
return;
}
// Check to grow _preorders[] array for the case when
// build_loop_tree_impl() adds new nodes.
check_grow_preorders();
}
}
else {
(void)bltstack.pop(); // Remove post-visited node from stack
}
}
}
//------------------------------build_loop_tree_impl---------------------------
int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
// ---- Post-pass Work ----
// Pre-walked but not post-walked nodes need a pre_order number.
// Tightest enclosing loop for this Node
IdealLoopTree *innermost = NULL;
// For all children, see if any edge is a backedge. If so, make a loop
// for it. Then find the tightest enclosing loop for the self Node.
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
Node* m = n->fast_out(i); // Child
if( n == m ) continue; // Ignore control self-cycles
if( !m->is_CFG() ) continue;// Ignore non-CFG edges
IdealLoopTree *l; // Child's loop
if( !is_postvisited(m) ) { // Child visited but not post-visited?
// Found a backedge
assert( get_preorder(m) < pre_order, "should be backedge" );
// Check for the RootNode, which is already a LoopNode and is allowed
// to have multiple "backedges".
if( m == C->root()) { // Found the root?
l = _ltree_root; // Root is the outermost LoopNode
} else { // Else found a nested loop
// Insert a LoopNode to mark this loop.
l = new IdealLoopTree(this, m, n);
} // End of Else found a nested loop
if( !has_loop(m) ) // If 'm' does not already have a loop set
set_loop(m, l); // Set loop header to loop now
} else { // Else not a nested loop
if( !_nodes[m->_idx] ) continue; // Dead code has no loop
l = get_loop(m); // Get previously determined loop
// If successor is header of a loop (nest), move up-loop till it
// is a member of some outer enclosing loop. Since there are no
// shared headers (I've split them already) I only need to go up
// at most 1 level.
while( l && l->_head == m ) // Successor heads loop?
l = l->_parent; // Move up 1 for me
// If this loop is not properly parented, then this loop
// has no exit path out, i.e. its an infinite loop.
if( !l ) {
// Make loop "reachable" from root so the CFG is reachable. Basically
// insert a bogus loop exit that is never taken. 'm', the loop head,
// points to 'n', one (of possibly many) fall-in paths. There may be
// many backedges as well.
// Here I set the loop to be the root loop. I could have, after
// inserting a bogus loop exit, restarted the recursion and found my
// new loop exit. This would make the infinite loop a first-class
// loop and it would then get properly optimized. What's the use of
// optimizing an infinite loop?
l = _ltree_root; // Oops, found infinite loop
if (!_verify_only) {
// Insert the NeverBranch between 'm' and it's control user.
NeverBranchNode *iff = new (C) NeverBranchNode( m );
_igvn.register_new_node_with_optimizer(iff);
set_loop(iff, l);
Node *if_t = new (C) CProjNode( iff, 0 );
_igvn.register_new_node_with_optimizer(if_t);
set_loop(if_t, l);
Node* cfg = NULL; // Find the One True Control User of m
for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
Node* x = m->fast_out(j);
if (x->is_CFG() && x != m && x != iff)
{ cfg = x; break; }
}
assert(cfg != NULL, "must find the control user of m");
uint k = 0; // Probably cfg->in(0)
while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
cfg->set_req( k, if_t ); // Now point to NeverBranch
// Now create the never-taken loop exit
Node *if_f = new (C) CProjNode( iff, 1 );
_igvn.register_new_node_with_optimizer(if_f);
set_loop(if_f, l);
// Find frame ptr for Halt. Relies on the optimizer
// V-N'ing. Easier and quicker than searching through
// the program structure.
Node *frame = new (C) ParmNode( C->start(), TypeFunc::FramePtr );
_igvn.register_new_node_with_optimizer(frame);
// Halt & Catch Fire
Node *halt = new (C) HaltNode( if_f, frame );
_igvn.register_new_node_with_optimizer(halt);
set_loop(halt, l);
C->root()->add_req(halt);
}
set_loop(C->root(), _ltree_root);
}
}
// Weeny check for irreducible. This child was already visited (this
// IS the post-work phase). Is this child's loop header post-visited
// as well? If so, then I found another entry into the loop.
if (!_verify_only) {
while( is_postvisited(l->_head) ) {
// found irreducible
l->_irreducible = 1; // = true
l = l->_parent;
_has_irreducible_loops = true;
// Check for bad CFG here to prevent crash, and bailout of compile
if (l == NULL) {
C->record_method_not_compilable("unhandled CFG detected during loop optimization");
return pre_order;
}
}
}
// This Node might be a decision point for loops. It is only if
// it's children belong to several different loops. The sort call
// does a trivial amount of work if there is only 1 child or all
// children belong to the same loop. If however, the children
// belong to different loops, the sort call will properly set the
// _parent pointers to show how the loops nest.
//
// In any case, it returns the tightest enclosing loop.
innermost = sort( l, innermost );
}
// Def-use info will have some dead stuff; dead stuff will have no
// loop decided on.
// Am I a loop header? If so fix up my parent's child and next ptrs.
if( innermost && innermost->_head == n ) {
assert( get_loop(n) == innermost, "" );
IdealLoopTree *p = innermost->_parent;
IdealLoopTree *l = innermost;
while( p && l->_head == n ) {
l->_next = p->_child; // Put self on parents 'next child'
p->_child = l; // Make self as first child of parent
l = p; // Now walk up the parent chain
p = l->_parent;
}
} else {
// Note that it is possible for a LoopNode to reach here, if the
// backedge has been made unreachable (hence the LoopNode no longer
// denotes a Loop, and will eventually be removed).
// Record tightest enclosing loop for self. Mark as post-visited.
set_loop(n, innermost);
// Also record has_call flag early on
if( innermost ) {
if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
// Do not count uncommon calls
if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
Node *iff = n->in(0)->in(0);
// No any calls for vectorized loops.
if( UseSuperWord || !iff->is_If() ||
(n->in(0)->Opcode() == Op_IfFalse &&
(1.0 - iff->as_If()->_prob) >= 0.01) ||
(iff->as_If()->_prob >= 0.01) )
innermost->_has_call = 1;
}
} else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
// Disable loop optimizations if the loop has a scalar replaceable
// allocation. This disabling may cause a potential performance lost
// if the allocation is not eliminated for some reason.
innermost->_allow_optimizations = false;
innermost->_has_call = 1; // = true
} else if (n->Opcode() == Op_SafePoint) {
// Record all safepoints in this loop.
if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
innermost->_safepts->push(n);
}
}
}
// Flag as post-visited now
set_postvisited(n);
return pre_order;
}
//------------------------------build_loop_early-------------------------------
// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
// First pass computes the earliest controlling node possible. This is the
// controlling input with the deepest dominating depth.
void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
while (worklist.size() != 0) {
// Use local variables nstack_top_n & nstack_top_i to cache values
// on nstack's top.
Node *nstack_top_n = worklist.pop();
uint nstack_top_i = 0;
//while_nstack_nonempty:
while (true) {
// Get parent node and next input's index from stack's top.
Node *n = nstack_top_n;
uint i = nstack_top_i;
uint cnt = n->req(); // Count of inputs
if (i == 0) { // Pre-process the node.
if( has_node(n) && // Have either loop or control already?
!has_ctrl(n) ) { // Have loop picked out already?
// During "merge_many_backedges" we fold up several nested loops
// into a single loop. This makes the members of the original
// loop bodies pointing to dead loops; they need to move up
// to the new UNION'd larger loop. I set the _head field of these
// dead loops to NULL and the _parent field points to the owning
// loop. Shades of UNION-FIND algorithm.
IdealLoopTree *ilt;
while( !(ilt = get_loop(n))->_head ) {
// Normally I would use a set_loop here. But in this one special
// case, it is legal (and expected) to change what loop a Node
// belongs to.
_nodes.map(n->_idx, (Node*)(ilt->_parent) );
}
// Remove safepoints ONLY if I've already seen I don't need one.
// (the old code here would yank a 2nd safepoint after seeing a
// first one, even though the 1st did not dominate in the loop body
// and thus could be avoided indefinitely)
if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
is_deleteable_safept(n)) {
Node *in = n->in(TypeFunc::Control);
lazy_replace(n,in); // Pull safepoint now
if (ilt->_safepts != NULL) {
ilt->_safepts->yank(n);
}
// Carry on with the recursion "as if" we are walking
// only the control input
if( !visited.test_set( in->_idx ) ) {
worklist.push(in); // Visit this guy later, using worklist
}
// Get next node from nstack:
// - skip n's inputs processing by setting i > cnt;
// - we also will not call set_early_ctrl(n) since
// has_node(n) == true (see the condition above).
i = cnt + 1;
}
}
} // if (i == 0)
// Visit all inputs
bool done = true; // Assume all n's inputs will be processed
while (i < cnt) {
Node *in = n->in(i);
++i;
if (in == NULL) continue;
if (in->pinned() && !in->is_CFG())
set_ctrl(in, in->in(0));
int is_visited = visited.test_set( in->_idx );
if (!has_node(in)) { // No controlling input yet?
assert( !in->is_CFG(), "CFG Node with no controlling input?" );
assert( !is_visited, "visit only once" );
nstack.push(n, i); // Save parent node and next input's index.
nstack_top_n = in; // Process current input now.
nstack_top_i = 0;
done = false; // Not all n's inputs processed.
break; // continue while_nstack_nonempty;
} else if (!is_visited) {
// This guy has a location picked out for him, but has not yet
// been visited. Happens to all CFG nodes, for instance.
// Visit him using the worklist instead of recursion, to break
// cycles. Since he has a location already we do not need to
// find his location before proceeding with the current Node.
worklist.push(in); // Visit this guy later, using worklist
}
}
if (done) {
// All of n's inputs have been processed, complete post-processing.
// Compute earliest point this Node can go.
// CFG, Phi, pinned nodes already know their controlling input.
if (!has_node(n)) {
// Record earliest legal location
set_early_ctrl( n );
}
if (nstack.is_empty()) {
// Finished all nodes on stack.
// Process next node on the worklist.
break;
}
// Get saved parent node and next input's index.
nstack_top_n = nstack.node();
nstack_top_i = nstack.index();
nstack.pop();
}
} // while (true)
}
}
//------------------------------dom_lca_internal--------------------------------
// Pair-wise LCA
Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
if( !n1 ) return n2; // Handle NULL original LCA
assert( n1->is_CFG(), "" );
assert( n2->is_CFG(), "" );
// find LCA of all uses
uint d1 = dom_depth(n1);
uint d2 = dom_depth(n2);
while (n1 != n2) {
if (d1 > d2) {
n1 = idom(n1);
d1 = dom_depth(n1);
} else if (d1 < d2) {
n2 = idom(n2);
d2 = dom_depth(n2);
} else {
// Here d1 == d2. Due to edits of the dominator-tree, sections
// of the tree might have the same depth. These sections have
// to be searched more carefully.
// Scan up all the n1's with equal depth, looking for n2.
Node *t1 = idom(n1);
while (dom_depth(t1) == d1) {
if (t1 == n2) return n2;
t1 = idom(t1);
}
// Scan up all the n2's with equal depth, looking for n1.
Node *t2 = idom(n2);
while (dom_depth(t2) == d2) {
if (t2 == n1) return n1;
t2 = idom(t2);
}
// Move up to a new dominator-depth value as well as up the dom-tree.
n1 = t1;
n2 = t2;
d1 = dom_depth(n1);
d2 = dom_depth(n2);
}
}
return n1;
}
//------------------------------compute_idom-----------------------------------
// Locally compute IDOM using dom_lca call. Correct only if the incoming
// IDOMs are correct.
Node *PhaseIdealLoop::compute_idom( Node *region ) const {
assert( region->is_Region(), "" );
Node *LCA = NULL;
for( uint i = 1; i < region->req(); i++ ) {
if( region->in(i) != C->top() )
LCA = dom_lca( LCA, region->in(i) );
}
return LCA;
}
bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
bool had_error = false;
#ifdef ASSERT
if (early != C->root()) {
// Make sure that there's a dominance path from use to LCA
Node* d = use;
while (d != LCA) {
d = idom(d);
if (d == C->root()) {
tty->print_cr("*** Use %d isn't dominated by def %s", use->_idx, n->_idx);
n->dump();
use->dump();
had_error = true;
break;
}
}
}
#endif
return had_error;
}
Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
// Compute LCA over list of uses
bool had_error = false;
Node *LCA = NULL;
for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
Node* c = n->fast_out(i);
if (_nodes[c->_idx] == NULL)
continue; // Skip the occasional dead node
if( c->is_Phi() ) { // For Phis, we must land above on the path
for( uint j=1; j<c->req(); j++ ) {// For all inputs
if( c->in(j) == n ) { // Found matching input?
Node *use = c->in(0)->in(j);
if (_verify_only && use->is_top()) continue;
LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
}
}
} else {
// For CFG data-users, use is in the block just prior
Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
}
}
assert(!had_error, "bad dominance");
return LCA;
}
//------------------------------get_late_ctrl----------------------------------
// Compute latest legal control.
Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
assert(early != NULL, "early control should not be NULL");
Node* LCA = compute_lca_of_uses(n, early);
#ifdef ASSERT
if (LCA == C->root() && LCA != early) {
// def doesn't dominate uses so print some useful debugging output
compute_lca_of_uses(n, early, true);
}
#endif
// if this is a load, check for anti-dependent stores
// We use a conservative algorithm to identify potential interfering
// instructions and for rescheduling the load. The users of the memory
// input of this load are examined. Any use which is not a load and is
// dominated by early is considered a potentially interfering store.
// This can produce false positives.
if (n->is_Load() && LCA != early) {
Node_List worklist;
Node *mem = n->in(MemNode::Memory);
for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
Node* s = mem->fast_out(i);
worklist.push(s);
}
while(worklist.size() != 0 && LCA != early) {
Node* s = worklist.pop();
if (s->is_Load()) {
continue;
} else if (s->is_MergeMem()) {
for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
Node* s1 = s->fast_out(i);
worklist.push(s1);
}
} else {
Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
assert(sctrl != NULL || s->outcnt() == 0, "must have control");
if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
}
}
}
}
assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
return LCA;
}
// true if CFG node d dominates CFG node n
bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
if (d == n)
return true;
assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
uint dd = dom_depth(d);
while (dom_depth(n) >= dd) {
if (n == d)
return true;
n = idom(n);
}
return false;
}
//------------------------------dom_lca_for_get_late_ctrl_internal-------------
// Pair-wise LCA with tags.
// Tag each index with the node 'tag' currently being processed
// before advancing up the dominator chain using idom().
// Later calls that find a match to 'tag' know that this path has already
// been considered in the current LCA (which is input 'n1' by convention).
// Since get_late_ctrl() is only called once for each node, the tag array
// does not need to be cleared between calls to get_late_ctrl().
// Algorithm trades a larger constant factor for better asymptotic behavior
//
Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
uint d1 = dom_depth(n1);
uint d2 = dom_depth(n2);
do {
if (d1 > d2) {
// current lca is deeper than n2
_dom_lca_tags.map(n1->_idx, tag);
n1 = idom(n1);
d1 = dom_depth(n1);
} else if (d1 < d2) {
// n2 is deeper than current lca
Node *memo = _dom_lca_tags[n2->_idx];
if( memo == tag ) {
return n1; // Return the current LCA
}
_dom_lca_tags.map(n2->_idx, tag);
n2 = idom(n2);
d2 = dom_depth(n2);
} else {
// Here d1 == d2. Due to edits of the dominator-tree, sections
// of the tree might have the same depth. These sections have
// to be searched more carefully.
// Scan up all the n1's with equal depth, looking for n2.
_dom_lca_tags.map(n1->_idx, tag);
Node *t1 = idom(n1);
while (dom_depth(t1) == d1) {
if (t1 == n2) return n2;
_dom_lca_tags.map(t1->_idx, tag);
t1 = idom(t1);
}
// Scan up all the n2's with equal depth, looking for n1.
_dom_lca_tags.map(n2->_idx, tag);
Node *t2 = idom(n2);
while (dom_depth(t2) == d2) {
if (t2 == n1) return n1;
_dom_lca_tags.map(t2->_idx, tag);
t2 = idom(t2);
}
// Move up to a new dominator-depth value as well as up the dom-tree.
n1 = t1;
n2 = t2;
d1 = dom_depth(n1);
d2 = dom_depth(n2);
}
} while (n1 != n2);
return n1;
}
//------------------------------init_dom_lca_tags------------------------------
// Tag could be a node's integer index, 32bits instead of 64bits in some cases
// Intended use does not involve any growth for the array, so it could
// be of fixed size.
void PhaseIdealLoop::init_dom_lca_tags() {
uint limit = C->unique() + 1;
_dom_lca_tags.map( limit, NULL );
#ifdef ASSERT
for( uint i = 0; i < limit; ++i ) {
assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
}
#endif // ASSERT
}
//------------------------------clear_dom_lca_tags------------------------------
// Tag could be a node's integer index, 32bits instead of 64bits in some cases
// Intended use does not involve any growth for the array, so it could
// be of fixed size.
void PhaseIdealLoop::clear_dom_lca_tags() {
uint limit = C->unique() + 1;
_dom_lca_tags.map( limit, NULL );
_dom_lca_tags.clear();
#ifdef ASSERT
for( uint i = 0; i < limit; ++i ) {
assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
}
#endif // ASSERT
}
//------------------------------build_loop_late--------------------------------
// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
// Second pass finds latest legal placement, and ideal loop placement.
void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
while (worklist.size() != 0) {
Node *n = worklist.pop();
// Only visit once
if (visited.test_set(n->_idx)) continue;
uint cnt = n->outcnt();
uint i = 0;
while (true) {
assert( _nodes[n->_idx], "no dead nodes" );
// Visit all children
if (i < cnt) {
Node* use = n->raw_out(i);
++i;
// Check for dead uses. Aggressively prune such junk. It might be
// dead in the global sense, but still have local uses so I cannot
// easily call 'remove_dead_node'.
if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
// Due to cycles, we might not hit the same fixed point in the verify
// pass as we do in the regular pass. Instead, visit such phis as
// simple uses of the loop head.
if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
if( !visited.test(use->_idx) )
worklist.push(use);
} else if( !visited.test_set(use->_idx) ) {
nstack.push(n, i); // Save parent and next use's index.
n = use; // Process all children of current use.
cnt = use->outcnt();
i = 0;
}
} else {
// Do not visit around the backedge of loops via data edges.
// push dead code onto a worklist
_deadlist.push(use);
}
} else {
// All of n's children have been processed, complete post-processing.
build_loop_late_post(n);
if (nstack.is_empty()) {
// Finished all nodes on stack.
// Process next node on the worklist.
break;
}
// Get saved parent node and next use's index. Visit the rest of uses.
n = nstack.node();
cnt = n->outcnt();
i = nstack.index();
nstack.pop();
}
}
}
}
//------------------------------build_loop_late_post---------------------------
// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
// Second pass finds latest legal placement, and ideal loop placement.
void PhaseIdealLoop::build_loop_late_post( Node *n ) {
if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
_igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops.
}
// CFG and pinned nodes already handled
if( n->in(0) ) {
if( n->in(0)->is_top() ) return; // Dead?
// We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
// _must_ be pinned (they have to observe their control edge of course).
// Unlike Stores (which modify an unallocable resource, the memory
// state), Mods/Loads can float around. So free them up.
bool pinned = true;
switch( n->Opcode() ) {
case Op_DivI:
case Op_DivF:
case Op_DivD:
case Op_ModI:
case Op_ModF:
case Op_ModD:
case Op_LoadB: // Same with Loads; they can sink
case Op_LoadUB: // during loop optimizations.
case Op_LoadUS:
case Op_LoadD:
case Op_LoadF:
case Op_LoadI:
case Op_LoadKlass:
case Op_LoadNKlass:
case Op_LoadL:
case Op_LoadS:
case Op_LoadP:
case Op_LoadN:
case Op_LoadRange:
case Op_LoadD_unaligned:
case Op_LoadL_unaligned:
case Op_StrComp: // Does a bunch of load-like effects
case Op_StrEquals:
case Op_StrIndexOf:
case Op_AryEq:
pinned = false;
}
if( pinned ) {
IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
if( !chosen_loop->_child ) // Inner loop?
chosen_loop->_body.push(n); // Collect inner loops
return;
}
} else { // No slot zero
if( n->is_CFG() ) { // CFG with no slot 0 is dead
_nodes.map(n->_idx,0); // No block setting, it's globally dead
return;
}
assert(!n->is_CFG() || n->outcnt() == 0, "");
}
// Do I have a "safe range" I can select over?
Node *early = get_ctrl(n);// Early location already computed
// Compute latest point this Node can go
Node *LCA = get_late_ctrl( n, early );
// LCA is NULL due to uses being dead
if( LCA == NULL ) {
#ifdef ASSERT
for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
}
#endif
_nodes.map(n->_idx, 0); // This node is useless
_deadlist.push(n);
return;
}
assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
Node *legal = LCA; // Walk 'legal' up the IDOM chain
Node *least = legal; // Best legal position so far
while( early != legal ) { // While not at earliest legal
#ifdef ASSERT
if (legal->is_Start() && !early->is_Root()) {
// Bad graph. Print idom path and fail.
dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
assert(false, "Bad graph detected in build_loop_late");
}
#endif
// Find least loop nesting depth
legal = idom(legal); // Bump up the IDOM tree
// Check for lower nesting depth
if( get_loop(legal)->_nest < get_loop(least)->_nest )
least = legal;
}
assert(early == legal || legal != C->root(), "bad dominance of inputs");
// Try not to place code on a loop entry projection
// which can inhibit range check elimination.
if (least != early) {
Node* ctrl_out = least->unique_ctrl_out();
if (ctrl_out && ctrl_out->is_CountedLoop() &&
least == ctrl_out->in(LoopNode::EntryControl)) {
Node* least_dom = idom(least);
if (get_loop(least_dom)->is_member(get_loop(least))) {
least = least_dom;
}
}
}
#ifdef ASSERT
// If verifying, verify that 'verify_me' has a legal location
// and choose it as our location.
if( _verify_me ) {
Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
Node *legal = LCA;
while( early != legal ) { // While not at earliest legal
if( legal == v_ctrl ) break; // Check for prior good location
legal = idom(legal) ;// Bump up the IDOM tree
}
// Check for prior good location
if( legal == v_ctrl ) least = legal; // Keep prior if found
}
#endif
// Assign discovered "here or above" point
least = find_non_split_ctrl(least);
set_ctrl(n, least);
// Collect inner loop bodies
IdealLoopTree *chosen_loop = get_loop(least);
if( !chosen_loop->_child ) // Inner loop?
chosen_loop->_body.push(n);// Collect inner loops
}
#ifdef ASSERT
void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
tty->print_cr(msg);
tty->print("n: "); n->dump();
tty->print("early(n): "); early->dump();
if (n->in(0) != NULL && !n->in(0)->is_top() &&
n->in(0) != early && !n->in(0)->is_Root()) {
tty->print("n->in(0): "); n->in(0)->dump();
}
for (uint i = 1; i < n->req(); i++) {
Node* in1 = n->in(i);
if (in1 != NULL && in1 != n && !in1->is_top()) {
tty->print("n->in(%d): ", i); in1->dump();
Node* in1_early = get_ctrl(in1);
tty->print("early(n->in(%d)): ", i); in1_early->dump();
if (in1->in(0) != NULL && !in1->in(0)->is_top() &&
in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
}
for (uint j = 1; j < in1->req(); j++) {
Node* in2 = in1->in(j);
if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
Node* in2_early = get_ctrl(in2);
tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
if (in2->in(0) != NULL && !in2->in(0)->is_top() &&
in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
}
}
}
}
}
tty->cr();
tty->print("LCA(n): "); LCA->dump();
for (uint i = 0; i < n->outcnt(); i++) {
Node* u1 = n->raw_out(i);
if (u1 == n)
continue;
tty->print("n->out(%d): ", i); u1->dump();
if (u1->is_CFG()) {
for (uint j = 0; j < u1->outcnt(); j++) {
Node* u2 = u1->raw_out(j);
if (u2 != u1 && u2 != n && u2->is_CFG()) {
tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
}
}
} else {
Node* u1_later = get_ctrl(u1);
tty->print("later(n->out(%d)): ", i); u1_later->dump();
if (u1->in(0) != NULL && !u1->in(0)->is_top() &&
u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
}
for (uint j = 0; j < u1->outcnt(); j++) {
Node* u2 = u1->raw_out(j);
if (u2 == n || u2 == u1)
continue;
tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
if (!u2->is_CFG()) {
Node* u2_later = get_ctrl(u2);
tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
if (u2->in(0) != NULL && !u2->in(0)->is_top() &&
u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
}
}
}
}
}
tty->cr();
int ct = 0;
Node *dbg_legal = LCA;
while(!dbg_legal->is_Start() && ct < 100) {
tty->print("idom[%d] ",ct); dbg_legal->dump();
ct++;
dbg_legal = idom(dbg_legal);
}
tty->cr();
}
#endif
#ifndef PRODUCT
//------------------------------dump-------------------------------------------
void PhaseIdealLoop::dump( ) const {
ResourceMark rm;
Arena* arena = Thread::current()->resource_area();
Node_Stack stack(arena, C->unique() >> 2);
Node_List rpo_list;
VectorSet visited(arena);
visited.set(C->top()->_idx);
rpo( C->root(), stack, visited, rpo_list );
// Dump root loop indexed by last element in PO order
dump( _ltree_root, rpo_list.size(), rpo_list );
}
void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
loop->dump_head();
// Now scan for CFG nodes in the same loop
for( uint j=idx; j > 0; j-- ) {
Node *n = rpo_list[j-1];
if( !_nodes[n->_idx] ) // Skip dead nodes
continue;
if( get_loop(n) != loop ) { // Wrong loop nest
if( get_loop(n)->_head == n && // Found nested loop?
get_loop(n)->_parent == loop )
dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly
continue;
}
// Dump controlling node
for( uint x = 0; x < loop->_nest; x++ )
tty->print(" ");
tty->print("C");
if( n == C->root() ) {
n->dump();
} else {
Node* cached_idom = idom_no_update(n);
Node *computed_idom = n->in(0);
if( n->is_Region() ) {
computed_idom = compute_idom(n);
// computed_idom() will return n->in(0) when idom(n) is an IfNode (or
// any MultiBranch ctrl node), so apply a similar transform to
// the cached idom returned from idom_no_update.
cached_idom = find_non_split_ctrl(cached_idom);
}
tty->print(" ID:%d",computed_idom->_idx);
n->dump();
if( cached_idom != computed_idom ) {
tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d",
computed_idom->_idx, cached_idom->_idx);
}
}
// Dump nodes it controls
for( uint k = 0; k < _nodes.Size(); k++ ) {
// (k < C->unique() && get_ctrl(find(k)) == n)
if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
Node *m = C->root()->find(k);
if( m && m->outcnt() > 0 ) {
if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p",
_nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
}
for( uint j = 0; j < loop->_nest; j++ )
tty->print(" ");
tty->print(" ");
m->dump();
}
}
}
}
}
// Collect a R-P-O for the whole CFG.
// Result list is in post-order (scan backwards for RPO)
void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
stk.push(start, 0);
visited.set(start->_idx);
while (stk.is_nonempty()) {
Node* m = stk.node();
uint idx = stk.index();
if (idx < m->outcnt()) {
stk.set_index(idx + 1);
Node* n = m->raw_out(idx);
if (n->is_CFG() && !visited.test_set(n->_idx)) {
stk.push(n, 0);
}
} else {
rpo_list.push(m);
stk.pop();
}
}
}
#endif
//=============================================================================
//------------------------------LoopTreeIterator-----------------------------------
// Advance to next loop tree using a preorder, left-to-right traversal.
void LoopTreeIterator::next() {
assert(!done(), "must not be done.");
if (_curnt->_child != NULL) {
_curnt = _curnt->_child;
} else if (_curnt->_next != NULL) {
_curnt = _curnt->_next;
} else {
while (_curnt != _root && _curnt->_next == NULL) {
_curnt = _curnt->_parent;
}
if (_curnt == _root) {
_curnt = NULL;
assert(done(), "must be done.");
} else {
assert(_curnt->_next != NULL, "must be more to do");
_curnt = _curnt->_next;
}
}
}
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