Java example source code file (split_if.cpp)
The split_if.cpp Java example source code
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
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*
* 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.
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#include "precompiled.hpp"
#include "memory/allocation.inline.hpp"
#include "opto/callnode.hpp"
#include "opto/connode.hpp"
#include "opto/loopnode.hpp"
//------------------------------split_thru_region------------------------------
// Split Node 'n' through merge point.
Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
uint wins = 0;
assert( n->is_CFG(), "" );
assert( region->is_Region(), "" );
Node *r = new (C) RegionNode( region->req() );
IdealLoopTree *loop = get_loop( n );
for( uint i = 1; i < region->req(); i++ ) {
Node *x = n->clone();
Node *in0 = n->in(0);
if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
for( uint j = 1; j < n->req(); j++ ) {
Node *in = n->in(j);
if( get_ctrl(in) == region )
x->set_req( j, in->in(i) );
}
_igvn.register_new_node_with_optimizer(x);
set_loop(x, loop);
set_idom(x, x->in(0), dom_depth(x->in(0))+1);
r->init_req(i, x);
}
// Record region
r->set_req(0,region); // Not a TRUE RegionNode
_igvn.register_new_node_with_optimizer(r);
set_loop(r, loop);
if( !loop->_child )
loop->_body.push(r);
return r;
}
//------------------------------split_up---------------------------------------
// Split block-local op up through the phis to empty the current block
bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
if( n->is_CFG() ) {
assert( n->in(0) != blk1, "Lousy candidate for split-if" );
return false;
}
if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
return false; // Not block local
if( n->is_Phi() ) return false; // Local PHIs are expected
// Recursively split-up inputs
for (uint i = 1; i < n->req(); i++) {
if( split_up( n->in(i), blk1, blk2 ) ) {
// Got split recursively and self went dead?
if (n->outcnt() == 0)
_igvn.remove_dead_node(n);
return true;
}
}
// Check for needing to clone-up a compare. Can't do that, it forces
// another (nested) split-if transform. Instead, clone it "down".
if( n->is_Cmp() ) {
assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
// Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
// sequence can have no other users and it must all reside in the split-if
// block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
// private, per-use versions of the Cmp and Bool are made. These sink to
// the CMove block. If the CMove is in the split-if block, then in the
// next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
Node *bol, *cmov;
if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
(bol = n->unique_out()->as_Bool()) &&
(get_ctrl(bol) == blk1 ||
get_ctrl(bol) == blk2) &&
bol->outcnt() == 1 &&
bol->unique_out()->is_CMove() &&
(cmov = bol->unique_out()->as_CMove()) &&
(get_ctrl(cmov) == blk1 ||
get_ctrl(cmov) == blk2) ) ) {
// Must clone down
#ifndef PRODUCT
if( PrintOpto && VerifyLoopOptimizations ) {
tty->print("Cloning down: ");
n->dump();
}
#endif
// Clone down any block-local BoolNode uses of this CmpNode
for (DUIterator i = n->outs(); n->has_out(i); i++) {
Node* bol = n->out(i);
assert( bol->is_Bool(), "" );
if (bol->outcnt() == 1) {
Node* use = bol->unique_out();
Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
if (use_c == blk1 || use_c == blk2) {
continue;
}
}
if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
// Recursively sink any BoolNode
#ifndef PRODUCT
if( PrintOpto && VerifyLoopOptimizations ) {
tty->print("Cloning down: ");
bol->dump();
}
#endif
for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
// Uses are either IfNodes or CMoves
Node* iff = bol->last_out(j);
assert( iff->in(1) == bol, "" );
// Get control block of either the CMove or the If input
Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
Node *x = bol->clone();
register_new_node(x, iff_ctrl);
_igvn.replace_input_of(iff, 1, x);
}
_igvn.remove_dead_node( bol );
--i;
}
}
// Clone down this CmpNode
for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
Node* bol = n->last_out(j);
assert( bol->in(1) == n, "" );
Node *x = n->clone();
register_new_node(x, get_ctrl(bol));
_igvn.replace_input_of(bol, 1, x);
}
_igvn.remove_dead_node( n );
return true;
}
}
// See if splitting-up a Store. Any anti-dep loads must go up as
// well. An anti-dep load might be in the wrong block, because in
// this particular layout/schedule we ignored anti-deps and allow
// memory to be alive twice. This only works if we do the same
// operations on anti-dep loads as we do their killing stores.
if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
// Get store's memory slice
int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
// Get memory-phi anti-dep loads will be using
Node *memphi = n->in(MemNode::Memory);
assert( memphi->is_Phi(), "" );
// Hoist any anti-dep load to the splitting block;
// it will then "split-up".
for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
Node *load = memphi->fast_out(i);
if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
set_ctrl(load,blk1);
}
}
// Found some other Node; must clone it up
#ifndef PRODUCT
if( PrintOpto && VerifyLoopOptimizations ) {
tty->print("Cloning up: ");
n->dump();
}
#endif
// ConvI2L may have type information on it which becomes invalid if
// it moves up in the graph so change any clones so widen the type
// to TypeLong::INT when pushing it up.
const Type* rtype = NULL;
if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) {
rtype = TypeLong::INT;
}
// Now actually split-up this guy. One copy per control path merging.
Node *phi = PhiNode::make_blank(blk1, n);
for( uint j = 1; j < blk1->req(); j++ ) {
Node *x = n->clone();
// Widen the type of the ConvI2L when pushing up.
if (rtype != NULL) x->as_Type()->set_type(rtype);
if( n->in(0) && n->in(0) == blk1 )
x->set_req( 0, blk1->in(j) );
for( uint i = 1; i < n->req(); i++ ) {
Node *m = n->in(i);
if( get_ctrl(m) == blk1 ) {
assert( m->in(0) == blk1, "" );
x->set_req( i, m->in(j) );
}
}
register_new_node( x, blk1->in(j) );
phi->init_req( j, x );
}
// Announce phi to optimizer
register_new_node(phi, blk1);
// Remove cloned-up value from optimizer; use phi instead
_igvn.replace_node( n, phi );
// (There used to be a self-recursive call to split_up() here,
// but it is not needed. All necessary forward walking is done
// by do_split_if() below.)
return true;
}
//------------------------------register_new_node------------------------------
void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
assert(!n->is_CFG(), "must be data node");
_igvn.register_new_node_with_optimizer(n);
set_ctrl(n, blk);
IdealLoopTree *loop = get_loop(blk);
if( !loop->_child )
loop->_body.push(n);
}
//------------------------------small_cache------------------------------------
struct small_cache : public Dict {
small_cache() : Dict( cmpkey, hashptr ) {}
Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
};
//------------------------------spinup-----------------------------------------
// "Spin up" the dominator tree, starting at the use site and stopping when we
// find the post-dominating point.
// We must be at the merge point which post-dominates 'new_false' and
// 'new_true'. Figure out which edges into the RegionNode eventually lead up
// to false and which to true. Put in a PhiNode to merge values; plug in
// the appropriate false-arm or true-arm values. If some path leads to the
// original IF, then insert a Phi recursively.
Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
if (use_blk->is_top()) // Handle dead uses
return use_blk;
Node *prior_n = (Node*)0xdeadbeef;
Node *n = use_blk; // Get path input
assert( use_blk != iff_dom, "" );
// Here's the "spinup" the dominator tree loop. Do a cache-check
// along the way, in case we've come this way before.
while( n != iff_dom ) { // Found post-dominating point?
prior_n = n;
n = idom(n); // Search higher
Node *s = cache->probe( prior_n ); // Check cache
if( s ) return s; // Cache hit!
}
Node *phi_post;
if( prior_n == new_false || prior_n == new_true ) {
phi_post = def->clone();
phi_post->set_req(0, prior_n );
register_new_node(phi_post, prior_n);
} else {
// This method handles both control uses (looking for Regions) or data
// uses (looking for Phis). If looking for a control use, then we need
// to insert a Region instead of a Phi; however Regions always exist
// previously (the hash_find_insert below would always hit) so we can
// return the existing Region.
if( def->is_CFG() ) {
phi_post = prior_n; // If looking for CFG, return prior
} else {
assert( def->is_Phi(), "" );
assert( prior_n->is_Region(), "must be a post-dominating merge point" );
// Need a Phi here
phi_post = PhiNode::make_blank(prior_n, def);
// Search for both true and false on all paths till find one.
for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
Node *t = _igvn.hash_find_insert(phi_post);
if( t ) { // See if we already have this one
// phi_post will not be used, so kill it
_igvn.remove_dead_node(phi_post);
phi_post->destruct();
phi_post = t;
} else {
register_new_node( phi_post, prior_n );
}
}
}
// Update cache everywhere
prior_n = (Node*)0xdeadbeef; // Reset IDOM walk
n = use_blk; // Get path input
// Spin-up the idom tree again, basically doing path-compression.
// Insert cache entries along the way, so that if we ever hit this
// point in the IDOM tree again we'll stop immediately on a cache hit.
while( n != iff_dom ) { // Found post-dominating point?
prior_n = n;
n = idom(n); // Search higher
cache->lru_insert( prior_n, phi_post ); // Fill cache
} // End of while not gone high enough
return phi_post;
}
//------------------------------find_use_block---------------------------------
// Find the block a USE is in. Normally USE's are in the same block as the
// using instruction. For Phi-USE's, the USE is in the predecessor block
// along the corresponding path.
Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
// CFG uses are their own block
if( use->is_CFG() )
return use;
if( use->is_Phi() ) { // Phi uses in prior block
// Grab the first Phi use; there may be many.
// Each will be handled as a separate iteration of
// the "while( phi->outcnt() )" loop.
uint j;
for( j = 1; j < use->req(); j++ )
if( use->in(j) == def )
break;
assert( j < use->req(), "def should be among use's inputs" );
return use->in(0)->in(j);
}
// Normal (non-phi) use
Node *use_blk = get_ctrl(use);
// Some uses are directly attached to the old (and going away)
// false and true branches.
if( use_blk == old_false ) {
use_blk = new_false;
set_ctrl(use, new_false);
}
if( use_blk == old_true ) {
use_blk = new_true;
set_ctrl(use, new_true);
}
if (use_blk == NULL) { // He's dead, Jim
_igvn.replace_node(use, C->top());
}
return use_blk;
}
//------------------------------handle_use-------------------------------------
// Handle uses of the merge point. Basically, split-if makes the merge point
// go away so all uses of the merge point must go away as well. Most block
// local uses have already been split-up, through the merge point. Uses from
// far below the merge point can't always be split up (e.g., phi-uses are
// pinned) and it makes too much stuff live. Instead we use a path-based
// solution to move uses down.
//
// If the use is along the pre-split-CFG true branch, then the new use will
// be from the post-split-CFG true merge point. Vice-versa for the false
// path. Some uses will be along both paths; then we sink the use to the
// post-dominating location; we may need to insert a Phi there.
void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {
Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
if( !use_blk ) return; // He's dead, Jim
// Walk up the dominator tree until I hit either the old IfFalse, the old
// IfTrue or the old If. Insert Phis where needed.
Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
// Found where this USE goes. Re-point him.
uint i;
for( i = 0; i < use->req(); i++ )
if( use->in(i) == def )
break;
assert( i < use->req(), "def should be among use's inputs" );
_igvn.replace_input_of(use, i, new_def);
}
//------------------------------do_split_if------------------------------------
// Found an If getting its condition-code input from a Phi in the same block.
// Split thru the Region.
void PhaseIdealLoop::do_split_if( Node *iff ) {
#ifndef PRODUCT
if( PrintOpto && VerifyLoopOptimizations )
tty->print_cr("Split-if");
if (TraceLoopOpts) {
tty->print_cr("SplitIf");
}
#endif
C->set_major_progress();
Node *region = iff->in(0);
Node *region_dom = idom(region);
// We are going to clone this test (and the control flow with it) up through
// the incoming merge point. We need to empty the current basic block.
// Clone any instructions which must be in this block up through the merge
// point.
DUIterator i, j;
bool progress = true;
while (progress) {
progress = false;
for (i = region->outs(); region->has_out(i); i++) {
Node* n = region->out(i);
if( n == region ) continue;
// The IF to be split is OK.
if( n == iff ) continue;
if( !n->is_Phi() ) { // Found pinned memory op or such
if (split_up(n, region, iff)) {
i = region->refresh_out_pos(i);
progress = true;
}
continue;
}
assert( n->in(0) == region, "" );
// Recursively split up all users of a Phi
for (j = n->outs(); n->has_out(j); j++) {
Node* m = n->out(j);
// If m is dead, throw it away, and declare progress
if (_nodes[m->_idx] == NULL) {
_igvn.remove_dead_node(m);
// fall through
}
else if (m != iff && split_up(m, region, iff)) {
// fall through
} else {
continue;
}
// Something unpredictable changed.
// Tell the iterators to refresh themselves, and rerun the loop.
i = region->refresh_out_pos(i);
j = region->refresh_out_pos(j);
progress = true;
}
}
}
// Now we have no instructions in the block containing the IF.
// Split the IF.
Node *new_iff = split_thru_region( iff, region );
// Replace both uses of 'new_iff' with Regions merging True/False
// paths. This makes 'new_iff' go dead.
Node *old_false, *old_true;
Node *new_false, *new_true;
for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
Node *ifp = iff->last_out(j2);
assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
ifp->set_req(0, new_iff);
Node *ifpx = split_thru_region( ifp, region );
// Replace 'If' projection of a Region with a Region of
// 'If' projections.
ifpx->set_req(0, ifpx); // A TRUE RegionNode
// Setup dominator info
set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
// Check for splitting loop tails
if( get_loop(iff)->tail() == ifp )
get_loop(iff)->_tail = ifpx;
// Replace in the graph with lazy-update mechanism
new_iff->set_req(0, new_iff); // hook self so it does not go dead
lazy_replace_proj( ifp, ifpx );
new_iff->set_req(0, region);
// Record bits for later xforms
if( ifp->Opcode() == Op_IfFalse ) {
old_false = ifp;
new_false = ifpx;
} else {
old_true = ifp;
new_true = ifpx;
}
}
_igvn.remove_dead_node(new_iff);
// Lazy replace IDOM info with the region's dominator
lazy_replace( iff, region_dom );
// Now make the original merge point go dead, by handling all its uses.
small_cache region_cache;
// Preload some control flow in region-cache
region_cache.lru_insert( new_false, new_false );
region_cache.lru_insert( new_true , new_true );
// Now handle all uses of the splitting block
for (DUIterator k = region->outs(); region->has_out(k); k++) {
Node* phi = region->out(k);
if (!phi->in(0)) { // Dead phi? Remove it
_igvn.remove_dead_node(phi);
} else if (phi == region) { // Found the self-reference
continue; // No roll-back of DUIterator
} else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
assert(phi->in(0) == region, "Inconsistent graph");
// Need a per-def cache. Phi represents a def, so make a cache
small_cache phi_cache;
// Inspect all Phi uses to make the Phi go dead
for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
Node* use = phi->last_out(l);
// Compute the new DEF for this USE. New DEF depends on the path
// taken from the original DEF to the USE. The new DEF may be some
// collection of PHI's merging values from different paths. The Phis
// inserted depend only on the location of the USE. We use a
// 2-element cache to handle multiple uses from the same block.
handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
} // End of while phi has uses
// Remove the dead Phi
_igvn.remove_dead_node( phi );
} else {
assert(phi->in(0) == region, "Inconsistent graph");
// Random memory op guarded by Region. Compute new DEF for USE.
handle_use(phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true);
}
// Every path above deletes a use of the region, except for the region
// self-cycle (which is needed by handle_use calling find_use_block
// calling get_ctrl calling get_ctrl_no_update looking for dead
// regions). So roll back the DUIterator innards.
--k;
} // End of while merge point has phis
assert(region->outcnt() == 1, "Only self reference should remain"); // Just Self on the Region
region->set_req(0, NULL); // Break the self-cycle
// Any leftover bits in the splitting block must not have depended on local
// Phi inputs (these have already been split-up). Hence it's safe to hoist
// these guys to the dominating point.
lazy_replace( region, region_dom );
#ifndef PRODUCT
if( VerifyLoopOptimizations ) verify();
#endif
}
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