Java example source code file (coalesce.cpp)
The coalesce.cpp Java example source code
/*
* Copyright (c) 1997, 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "memory/allocation.inline.hpp"
#include "opto/block.hpp"
#include "opto/cfgnode.hpp"
#include "opto/chaitin.hpp"
#include "opto/coalesce.hpp"
#include "opto/connode.hpp"
#include "opto/indexSet.hpp"
#include "opto/machnode.hpp"
#include "opto/matcher.hpp"
#include "opto/regmask.hpp"
#ifndef PRODUCT
void PhaseCoalesce::dump(Node *n) const {
// Being a const function means I cannot use 'Find'
uint r = _phc._lrg_map.find(n);
tty->print("L%d/N%d ",r,n->_idx);
}
void PhaseCoalesce::dump() const {
// I know I have a block layout now, so I can print blocks in a loop
for( uint i=0; i<_phc._cfg.number_of_blocks(); i++ ) {
uint j;
Block* b = _phc._cfg.get_block(i);
// Print a nice block header
tty->print("B%d: ",b->_pre_order);
for( j=1; j<b->num_preds(); j++ )
tty->print("B%d ", _phc._cfg.get_block_for_node(b->pred(j))->_pre_order);
tty->print("-> ");
for( j=0; j<b->_num_succs; j++ )
tty->print("B%d ",b->_succs[j]->_pre_order);
tty->print(" IDom: B%d/#%d\n", b->_idom ? b->_idom->_pre_order : 0, b->_dom_depth);
uint cnt = b->number_of_nodes();
for( j=0; j<cnt; j++ ) {
Node *n = b->get_node(j);
dump( n );
tty->print("\t%s\t",n->Name());
// Dump the inputs
uint k; // Exit value of loop
for( k=0; k<n->req(); k++ ) // For all required inputs
if( n->in(k) ) dump( n->in(k) );
else tty->print("_ ");
int any_prec = 0;
for( ; k<n->len(); k++ ) // For all precedence inputs
if( n->in(k) ) {
if( !any_prec++ ) tty->print(" |");
dump( n->in(k) );
}
// Dump node-specific info
n->dump_spec(tty);
tty->print("\n");
}
tty->print("\n");
}
}
#endif
// Combine the live ranges def'd by these 2 Nodes. N2 is an input to N1.
void PhaseCoalesce::combine_these_two(Node *n1, Node *n2) {
uint lr1 = _phc._lrg_map.find(n1);
uint lr2 = _phc._lrg_map.find(n2);
if( lr1 != lr2 && // Different live ranges already AND
!_phc._ifg->test_edge_sq( lr1, lr2 ) ) { // Do not interfere
LRG *lrg1 = &_phc.lrgs(lr1);
LRG *lrg2 = &_phc.lrgs(lr2);
// Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
// Now, why is int->oop OK? We end up declaring a raw-pointer as an oop
// and in general that's a bad thing. However, int->oop conversions only
// happen at GC points, so the lifetime of the misclassified raw-pointer
// is from the CheckCastPP (that converts it to an oop) backwards up
// through a merge point and into the slow-path call, and around the
// diamond up to the heap-top check and back down into the slow-path call.
// The misclassified raw pointer is NOT live across the slow-path call,
// and so does not appear in any GC info, so the fact that it is
// misclassified is OK.
if( (lrg1->_is_oop || !lrg2->_is_oop) && // not an oop->int cast AND
// Compatible final mask
lrg1->mask().overlap( lrg2->mask() ) ) {
// Merge larger into smaller.
if( lr1 > lr2 ) {
uint tmp = lr1; lr1 = lr2; lr2 = tmp;
Node *n = n1; n1 = n2; n2 = n;
LRG *ltmp = lrg1; lrg1 = lrg2; lrg2 = ltmp;
}
// Union lr2 into lr1
_phc.Union( n1, n2 );
if (lrg1->_maxfreq < lrg2->_maxfreq)
lrg1->_maxfreq = lrg2->_maxfreq;
// Merge in the IFG
_phc._ifg->Union( lr1, lr2 );
// Combine register restrictions
lrg1->AND(lrg2->mask());
}
}
}
// Copy coalescing
void PhaseCoalesce::coalesce_driver() {
verify();
// Coalesce from high frequency to low
for (uint i = 0; i < _phc._cfg.number_of_blocks(); i++) {
coalesce(_phc._blks[i]);
}
}
// I am inserting copies to come out of SSA form. In the general case, I am
// doing a parallel renaming. I'm in the Named world now, so I can't do a
// general parallel renaming. All the copies now use "names" (live-ranges)
// to carry values instead of the explicit use-def chains. Suppose I need to
// insert 2 copies into the same block. They copy L161->L128 and L128->L132.
// If I insert them in the wrong order then L128 will get clobbered before it
// can get used by the second copy. This cannot happen in the SSA model;
// direct use-def chains get me the right value. It DOES happen in the named
// model so I have to handle the reordering of copies.
//
// In general, I need to topo-sort the placed copies to avoid conflicts.
// Its possible to have a closed cycle of copies (e.g., recirculating the same
// values around a loop). In this case I need a temp to break the cycle.
void PhaseAggressiveCoalesce::insert_copy_with_overlap( Block *b, Node *copy, uint dst_name, uint src_name ) {
// Scan backwards for the locations of the last use of the dst_name.
// I am about to clobber the dst_name, so the copy must be inserted
// after the last use. Last use is really first-use on a backwards scan.
uint i = b->end_idx()-1;
while(1) {
Node *n = b->get_node(i);
// Check for end of virtual copies; this is also the end of the
// parallel renaming effort.
if (n->_idx < _unique) {
break;
}
uint idx = n->is_Copy();
assert( idx || n->is_Con() || n->is_MachProj(), "Only copies during parallel renaming" );
if (idx && _phc._lrg_map.find(n->in(idx)) == dst_name) {
break;
}
i--;
}
uint last_use_idx = i;
// Also search for any kill of src_name that exits the block.
// Since the copy uses src_name, I have to come before any kill.
uint kill_src_idx = b->end_idx();
// There can be only 1 kill that exits any block and that is
// the last kill. Thus it is the first kill on a backwards scan.
i = b->end_idx()-1;
while (1) {
Node *n = b->get_node(i);
// Check for end of virtual copies; this is also the end of the
// parallel renaming effort.
if (n->_idx < _unique) {
break;
}
assert( n->is_Copy() || n->is_Con() || n->is_MachProj(), "Only copies during parallel renaming" );
if (_phc._lrg_map.find(n) == src_name) {
kill_src_idx = i;
break;
}
i--;
}
// Need a temp? Last use of dst comes after the kill of src?
if (last_use_idx >= kill_src_idx) {
// Need to break a cycle with a temp
uint idx = copy->is_Copy();
Node *tmp = copy->clone();
uint max_lrg_id = _phc._lrg_map.max_lrg_id();
_phc.new_lrg(tmp, max_lrg_id);
_phc._lrg_map.set_max_lrg_id(max_lrg_id + 1);
// Insert new temp between copy and source
tmp ->set_req(idx,copy->in(idx));
copy->set_req(idx,tmp);
// Save source in temp early, before source is killed
b->insert_node(tmp, kill_src_idx);
_phc._cfg.map_node_to_block(tmp, b);
last_use_idx++;
}
// Insert just after last use
b->insert_node(copy, last_use_idx + 1);
}
void PhaseAggressiveCoalesce::insert_copies( Matcher &matcher ) {
// We do LRGs compressing and fix a liveout data only here since the other
// place in Split() is guarded by the assert which we never hit.
_phc._lrg_map.compress_uf_map_for_nodes();
// Fix block's liveout data for compressed live ranges.
for (uint lrg = 1; lrg < _phc._lrg_map.max_lrg_id(); lrg++) {
uint compressed_lrg = _phc._lrg_map.find(lrg);
if (lrg != compressed_lrg) {
for (uint bidx = 0; bidx < _phc._cfg.number_of_blocks(); bidx++) {
IndexSet *liveout = _phc._live->live(_phc._cfg.get_block(bidx));
if (liveout->member(lrg)) {
liveout->remove(lrg);
liveout->insert(compressed_lrg);
}
}
}
}
// All new nodes added are actual copies to replace virtual copies.
// Nodes with index less than '_unique' are original, non-virtual Nodes.
_unique = C->unique();
for (uint i = 0; i < _phc._cfg.number_of_blocks(); i++) {
C->check_node_count(NodeLimitFudgeFactor, "out of nodes in coalesce");
if (C->failing()) return;
Block *b = _phc._cfg.get_block(i);
uint cnt = b->num_preds(); // Number of inputs to the Phi
for( uint l = 1; l<b->number_of_nodes(); l++ ) {
Node *n = b->get_node(l);
// Do not use removed-copies, use copied value instead
uint ncnt = n->req();
for( uint k = 1; k<ncnt; k++ ) {
Node *copy = n->in(k);
uint cidx = copy->is_Copy();
if( cidx ) {
Node *def = copy->in(cidx);
if (_phc._lrg_map.find(copy) == _phc._lrg_map.find(def)) {
n->set_req(k, def);
}
}
}
// Remove any explicit copies that get coalesced.
uint cidx = n->is_Copy();
if( cidx ) {
Node *def = n->in(cidx);
if (_phc._lrg_map.find(n) == _phc._lrg_map.find(def)) {
n->replace_by(def);
n->set_req(cidx,NULL);
b->remove_node(l);
l--;
continue;
}
}
if (n->is_Phi()) {
// Get the chosen name for the Phi
uint phi_name = _phc._lrg_map.find(n);
// Ignore the pre-allocated specials
if (!phi_name) {
continue;
}
// Check for mismatch inputs to Phi
for (uint j = 1; j < cnt; j++) {
Node *m = n->in(j);
uint src_name = _phc._lrg_map.find(m);
if (src_name != phi_name) {
Block *pred = _phc._cfg.get_block_for_node(b->pred(j));
Node *copy;
assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
// Rematerialize constants instead of copying them
if( m->is_Mach() && m->as_Mach()->is_Con() &&
m->as_Mach()->rematerialize() ) {
copy = m->clone();
// Insert the copy in the predecessor basic block
pred->add_inst(copy);
// Copy any flags as well
_phc.clone_projs(pred, pred->end_idx(), m, copy, _phc._lrg_map);
} else {
const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
copy = new (C) MachSpillCopyNode(m, *rm, *rm);
// Find a good place to insert. Kinda tricky, use a subroutine
insert_copy_with_overlap(pred,copy,phi_name,src_name);
}
// Insert the copy in the use-def chain
n->set_req(j, copy);
_phc._cfg.map_node_to_block(copy, pred);
// Extend ("register allocate") the names array for the copy.
_phc._lrg_map.extend(copy->_idx, phi_name);
} // End of if Phi names do not match
} // End of for all inputs to Phi
} else { // End of if Phi
// Now check for 2-address instructions
uint idx;
if( n->is_Mach() && (idx=n->as_Mach()->two_adr()) ) {
// Get the chosen name for the Node
uint name = _phc._lrg_map.find(n);
assert (name, "no 2-address specials");
// Check for name mis-match on the 2-address input
Node *m = n->in(idx);
if (_phc._lrg_map.find(m) != name) {
Node *copy;
assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
// At this point it is unsafe to extend live ranges (6550579).
// Rematerialize only constants as we do for Phi above.
if(m->is_Mach() && m->as_Mach()->is_Con() &&
m->as_Mach()->rematerialize()) {
copy = m->clone();
// Insert the copy in the basic block, just before us
b->insert_node(copy, l++);
l += _phc.clone_projs(b, l, m, copy, _phc._lrg_map);
} else {
const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
copy = new (C) MachSpillCopyNode(m, *rm, *rm);
// Insert the copy in the basic block, just before us
b->insert_node(copy, l++);
}
// Insert the copy in the use-def chain
n->set_req(idx, copy);
// Extend ("register allocate") the names array for the copy.
_phc._lrg_map.extend(copy->_idx, name);
_phc._cfg.map_node_to_block(copy, b);
}
} // End of is two-adr
// Insert a copy at a debug use for a lrg which has high frequency
if (b->_freq < OPTO_DEBUG_SPLIT_FREQ || _phc._cfg.is_uncommon(b)) {
// Walk the debug inputs to the node and check for lrg freq
JVMState* jvms = n->jvms();
uint debug_start = jvms ? jvms->debug_start() : 999999;
uint debug_end = jvms ? jvms->debug_end() : 999999;
for(uint inpidx = debug_start; inpidx < debug_end; inpidx++) {
// Do not split monitors; they are only needed for debug table
// entries and need no code.
if (jvms->is_monitor_use(inpidx)) {
continue;
}
Node *inp = n->in(inpidx);
uint nidx = _phc._lrg_map.live_range_id(inp);
LRG &lrg = lrgs(nidx);
// If this lrg has a high frequency use/def
if( lrg._maxfreq >= _phc.high_frequency_lrg() ) {
// If the live range is also live out of this block (like it
// would be for a fast/slow idiom), the normal spill mechanism
// does an excellent job. If it is not live out of this block
// (like it would be for debug info to uncommon trap) splitting
// the live range now allows a better allocation in the high
// frequency blocks.
// Build_IFG_virtual has converted the live sets to
// live-IN info, not live-OUT info.
uint k;
for( k=0; k < b->_num_succs; k++ )
if( _phc._live->live(b->_succs[k])->member( nidx ) )
break; // Live in to some successor block?
if( k < b->_num_succs )
continue; // Live out; do not pre-split
// Split the lrg at this use
const RegMask *rm = C->matcher()->idealreg2spillmask[inp->ideal_reg()];
Node *copy = new (C) MachSpillCopyNode( inp, *rm, *rm );
// Insert the copy in the use-def chain
n->set_req(inpidx, copy );
// Insert the copy in the basic block, just before us
b->insert_node(copy, l++);
// Extend ("register allocate") the names array for the copy.
uint max_lrg_id = _phc._lrg_map.max_lrg_id();
_phc.new_lrg(copy, max_lrg_id);
_phc._lrg_map.set_max_lrg_id(max_lrg_id + 1);
_phc._cfg.map_node_to_block(copy, b);
//tty->print_cr("Split a debug use in Aggressive Coalesce");
} // End of if high frequency use/def
} // End of for all debug inputs
} // End of if low frequency safepoint
} // End of if Phi
} // End of for all instructions
} // End of for all blocks
}
// Aggressive (but pessimistic) copy coalescing of a single block
// The following coalesce pass represents a single round of aggressive
// pessimistic coalesce. "Aggressive" means no attempt to preserve
// colorability when coalescing. This occasionally means more spills, but
// it also means fewer rounds of coalescing for better code - and that means
// faster compiles.
// "Pessimistic" means we do not hit the fixed point in one pass (and we are
// reaching for the least fixed point to boot). This is typically solved
// with a few more rounds of coalescing, but the compiler must run fast. We
// could optimistically coalescing everything touching PhiNodes together
// into one big live range, then check for self-interference. Everywhere
// the live range interferes with self it would have to be split. Finding
// the right split points can be done with some heuristics (based on
// expected frequency of edges in the live range). In short, it's a real
// research problem and the timeline is too short to allow such research.
// Further thoughts: (1) build the LR in a pass, (2) find self-interference
// in another pass, (3) per each self-conflict, split, (4) split by finding
// the low-cost cut (min-cut) of the LR, (5) edges in the LR are weighted
// according to the GCM algorithm (or just exec freq on CFG edges).
void PhaseAggressiveCoalesce::coalesce( Block *b ) {
// Copies are still "virtual" - meaning we have not made them explicitly
// copies. Instead, Phi functions of successor blocks have mis-matched
// live-ranges. If I fail to coalesce, I'll have to insert a copy to line
// up the live-ranges. Check for Phis in successor blocks.
uint i;
for( i=0; i<b->_num_succs; i++ ) {
Block *bs = b->_succs[i];
// Find index of 'b' in 'bs' predecessors
uint j=1;
while (_phc._cfg.get_block_for_node(bs->pred(j)) != b) {
j++;
}
// Visit all the Phis in successor block
for( uint k = 1; k<bs->number_of_nodes(); k++ ) {
Node *n = bs->get_node(k);
if( !n->is_Phi() ) break;
combine_these_two( n, n->in(j) );
}
} // End of for all successor blocks
// Check _this_ block for 2-address instructions and copies.
uint cnt = b->end_idx();
for( i = 1; i<cnt; i++ ) {
Node *n = b->get_node(i);
uint idx;
// 2-address instructions have a virtual Copy matching their input
// to their output
if (n->is_Mach() && (idx = n->as_Mach()->two_adr())) {
MachNode *mach = n->as_Mach();
combine_these_two(mach, mach->in(idx));
}
} // End of for all instructions in block
}
PhaseConservativeCoalesce::PhaseConservativeCoalesce(PhaseChaitin &chaitin) : PhaseCoalesce(chaitin) {
_ulr.initialize(_phc._lrg_map.max_lrg_id());
}
void PhaseConservativeCoalesce::verify() {
#ifdef ASSERT
_phc.set_was_low();
#endif
}
void PhaseConservativeCoalesce::union_helper( Node *lr1_node, Node *lr2_node, uint lr1, uint lr2, Node *src_def, Node *dst_copy, Node *src_copy, Block *b, uint bindex ) {
// Join live ranges. Merge larger into smaller. Union lr2 into lr1 in the
// union-find tree
_phc.Union( lr1_node, lr2_node );
// Single-def live range ONLY if both live ranges are single-def.
// If both are single def, then src_def powers one live range
// and def_copy powers the other. After merging, src_def powers
// the combined live range.
lrgs(lr1)._def = (lrgs(lr1).is_multidef() ||
lrgs(lr2).is_multidef() )
? NodeSentinel : src_def;
lrgs(lr2)._def = NULL; // No def for lrg 2
lrgs(lr2).Clear(); // Force empty mask for LRG 2
//lrgs(lr2)._size = 0; // Live-range 2 goes dead
lrgs(lr1)._is_oop |= lrgs(lr2)._is_oop;
lrgs(lr2)._is_oop = 0; // In particular, not an oop for GC info
if (lrgs(lr1)._maxfreq < lrgs(lr2)._maxfreq)
lrgs(lr1)._maxfreq = lrgs(lr2)._maxfreq;
// Copy original value instead. Intermediate copies go dead, and
// the dst_copy becomes useless.
int didx = dst_copy->is_Copy();
dst_copy->set_req( didx, src_def );
// Add copy to free list
// _phc.free_spillcopy(b->_nodes[bindex]);
assert( b->get_node(bindex) == dst_copy, "" );
dst_copy->replace_by( dst_copy->in(didx) );
dst_copy->set_req( didx, NULL);
b->remove_node(bindex);
if( bindex < b->_ihrp_index ) b->_ihrp_index--;
if( bindex < b->_fhrp_index ) b->_fhrp_index--;
// Stretched lr1; add it to liveness of intermediate blocks
Block *b2 = _phc._cfg.get_block_for_node(src_copy);
while( b != b2 ) {
b = _phc._cfg.get_block_for_node(b->pred(1));
_phc._live->live(b)->insert(lr1);
}
}
// Factored code from copy_copy that computes extra interferences from
// lengthening a live range by double-coalescing.
uint PhaseConservativeCoalesce::compute_separating_interferences(Node *dst_copy, Node *src_copy, Block *b, uint bindex, RegMask &rm, uint reg_degree, uint rm_size, uint lr1, uint lr2 ) {
assert(!lrgs(lr1)._fat_proj, "cannot coalesce fat_proj");
assert(!lrgs(lr2)._fat_proj, "cannot coalesce fat_proj");
Node *prev_copy = dst_copy->in(dst_copy->is_Copy());
Block *b2 = b;
uint bindex2 = bindex;
while( 1 ) {
// Find previous instruction
bindex2--; // Chain backwards 1 instruction
while( bindex2 == 0 ) { // At block start, find prior block
assert( b2->num_preds() == 2, "cannot double coalesce across c-flow" );
b2 = _phc._cfg.get_block_for_node(b2->pred(1));
bindex2 = b2->end_idx()-1;
}
// Get prior instruction
assert(bindex2 < b2->number_of_nodes(), "index out of bounds");
Node *x = b2->get_node(bindex2);
if( x == prev_copy ) { // Previous copy in copy chain?
if( prev_copy == src_copy)// Found end of chain and all interferences
break; // So break out of loop
// Else work back one in copy chain
prev_copy = prev_copy->in(prev_copy->is_Copy());
} else { // Else collect interferences
uint lidx = _phc._lrg_map.find(x);
// Found another def of live-range being stretched?
if(lidx == lr1) {
return max_juint;
}
if(lidx == lr2) {
return max_juint;
}
// If we attempt to coalesce across a bound def
if( lrgs(lidx).is_bound() ) {
// Do not let the coalesced LRG expect to get the bound color
rm.SUBTRACT( lrgs(lidx).mask() );
// Recompute rm_size
rm_size = rm.Size();
//if( rm._flags ) rm_size += 1000000;
if( reg_degree >= rm_size ) return max_juint;
}
if( rm.overlap(lrgs(lidx).mask()) ) {
// Insert lidx into union LRG; returns TRUE if actually inserted
if( _ulr.insert(lidx) ) {
// Infinite-stack neighbors do not alter colorability, as they
// can always color to some other color.
if( !lrgs(lidx).mask().is_AllStack() ) {
// If this coalesce will make any new neighbor uncolorable,
// do not coalesce.
if( lrgs(lidx).just_lo_degree() )
return max_juint;
// Bump our degree
if( ++reg_degree >= rm_size )
return max_juint;
} // End of if not infinite-stack neighbor
} // End of if actually inserted
} // End of if live range overlaps
} // End of else collect interferences for 1 node
} // End of while forever, scan back for interferences
return reg_degree;
}
void PhaseConservativeCoalesce::update_ifg(uint lr1, uint lr2, IndexSet *n_lr1, IndexSet *n_lr2) {
// Some original neighbors of lr1 might have gone away
// because the constrained register mask prevented them.
// Remove lr1 from such neighbors.
IndexSetIterator one(n_lr1);
uint neighbor;
LRG &lrg1 = lrgs(lr1);
while ((neighbor = one.next()) != 0)
if( !_ulr.member(neighbor) )
if( _phc._ifg->neighbors(neighbor)->remove(lr1) )
lrgs(neighbor).inc_degree( -lrg1.compute_degree(lrgs(neighbor)) );
// lr2 is now called (coalesced into) lr1.
// Remove lr2 from the IFG.
IndexSetIterator two(n_lr2);
LRG &lrg2 = lrgs(lr2);
while ((neighbor = two.next()) != 0)
if( _phc._ifg->neighbors(neighbor)->remove(lr2) )
lrgs(neighbor).inc_degree( -lrg2.compute_degree(lrgs(neighbor)) );
// Some neighbors of intermediate copies now interfere with the
// combined live range.
IndexSetIterator three(&_ulr);
while ((neighbor = three.next()) != 0)
if( _phc._ifg->neighbors(neighbor)->insert(lr1) )
lrgs(neighbor).inc_degree( lrg1.compute_degree(lrgs(neighbor)) );
}
static void record_bias( const PhaseIFG *ifg, int lr1, int lr2 ) {
// Tag copy bias here
if( !ifg->lrgs(lr1)._copy_bias )
ifg->lrgs(lr1)._copy_bias = lr2;
if( !ifg->lrgs(lr2)._copy_bias )
ifg->lrgs(lr2)._copy_bias = lr1;
}
// See if I can coalesce a series of multiple copies together. I need the
// final dest copy and the original src copy. They can be the same Node.
// Compute the compatible register masks.
bool PhaseConservativeCoalesce::copy_copy(Node *dst_copy, Node *src_copy, Block *b, uint bindex) {
if (!dst_copy->is_SpillCopy()) {
return false;
}
if (!src_copy->is_SpillCopy()) {
return false;
}
Node *src_def = src_copy->in(src_copy->is_Copy());
uint lr1 = _phc._lrg_map.find(dst_copy);
uint lr2 = _phc._lrg_map.find(src_def);
// Same live ranges already?
if (lr1 == lr2) {
return false;
}
// Interfere?
if (_phc._ifg->test_edge_sq(lr1, lr2)) {
return false;
}
// Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
if (!lrgs(lr1)._is_oop && lrgs(lr2)._is_oop) { // not an oop->int cast
return false;
}
// Coalescing between an aligned live range and a mis-aligned live range?
// No, no! Alignment changes how we count degree.
if (lrgs(lr1)._fat_proj != lrgs(lr2)._fat_proj) {
return false;
}
// Sort; use smaller live-range number
Node *lr1_node = dst_copy;
Node *lr2_node = src_def;
if (lr1 > lr2) {
uint tmp = lr1; lr1 = lr2; lr2 = tmp;
lr1_node = src_def; lr2_node = dst_copy;
}
// Check for compatibility of the 2 live ranges by
// intersecting their allowed register sets.
RegMask rm = lrgs(lr1).mask();
rm.AND(lrgs(lr2).mask());
// Number of bits free
uint rm_size = rm.Size();
if (UseFPUForSpilling && rm.is_AllStack() ) {
// Don't coalesce when frequency difference is large
Block *dst_b = _phc._cfg.get_block_for_node(dst_copy);
Block *src_def_b = _phc._cfg.get_block_for_node(src_def);
if (src_def_b->_freq > 10*dst_b->_freq )
return false;
}
// If we can use any stack slot, then effective size is infinite
if( rm.is_AllStack() ) rm_size += 1000000;
// Incompatible masks, no way to coalesce
if( rm_size == 0 ) return false;
// Another early bail-out test is when we are double-coalescing and the
// 2 copies are separated by some control flow.
if( dst_copy != src_copy ) {
Block *src_b = _phc._cfg.get_block_for_node(src_copy);
Block *b2 = b;
while( b2 != src_b ) {
if( b2->num_preds() > 2 ){// Found merge-point
_phc._lost_opp_cflow_coalesce++;
// extra record_bias commented out because Chris believes it is not
// productive. Since we can record only 1 bias, we want to choose one
// that stands a chance of working and this one probably does not.
//record_bias( _phc._lrgs, lr1, lr2 );
return false; // To hard to find all interferences
}
b2 = _phc._cfg.get_block_for_node(b2->pred(1));
}
}
// Union the two interference sets together into '_ulr'
uint reg_degree = _ulr.lrg_union( lr1, lr2, rm_size, _phc._ifg, rm );
if( reg_degree >= rm_size ) {
record_bias( _phc._ifg, lr1, lr2 );
return false;
}
// Now I need to compute all the interferences between dst_copy and
// src_copy. I'm not willing visit the entire interference graph, so
// I limit my search to things in dst_copy's block or in a straight
// line of previous blocks. I give up at merge points or when I get
// more interferences than my degree. I can stop when I find src_copy.
if( dst_copy != src_copy ) {
reg_degree = compute_separating_interferences(dst_copy, src_copy, b, bindex, rm, rm_size, reg_degree, lr1, lr2 );
if( reg_degree == max_juint ) {
record_bias( _phc._ifg, lr1, lr2 );
return false;
}
} // End of if dst_copy & src_copy are different
// ---- THE COMBINED LRG IS COLORABLE ----
// YEAH - Now coalesce this copy away
assert( lrgs(lr1).num_regs() == lrgs(lr2).num_regs(), "" );
IndexSet *n_lr1 = _phc._ifg->neighbors(lr1);
IndexSet *n_lr2 = _phc._ifg->neighbors(lr2);
// Update the interference graph
update_ifg(lr1, lr2, n_lr1, n_lr2);
_ulr.remove(lr1);
// Uncomment the following code to trace Coalescing in great detail.
//
//if (false) {
// tty->cr();
// tty->print_cr("#######################################");
// tty->print_cr("union %d and %d", lr1, lr2);
// n_lr1->dump();
// n_lr2->dump();
// tty->print_cr("resulting set is");
// _ulr.dump();
//}
// Replace n_lr1 with the new combined live range. _ulr will use
// n_lr1's old memory on the next iteration. n_lr2 is cleared to
// send its internal memory to the free list.
_ulr.swap(n_lr1);
_ulr.clear();
n_lr2->clear();
lrgs(lr1).set_degree( _phc._ifg->effective_degree(lr1) );
lrgs(lr2).set_degree( 0 );
// Join live ranges. Merge larger into smaller. Union lr2 into lr1 in the
// union-find tree
union_helper( lr1_node, lr2_node, lr1, lr2, src_def, dst_copy, src_copy, b, bindex );
// Combine register restrictions
lrgs(lr1).set_mask(rm);
lrgs(lr1).compute_set_mask_size();
lrgs(lr1)._cost += lrgs(lr2)._cost;
lrgs(lr1)._area += lrgs(lr2)._area;
// While its uncommon to successfully coalesce live ranges that started out
// being not-lo-degree, it can happen. In any case the combined coalesced
// live range better Simplify nicely.
lrgs(lr1)._was_lo = 1;
// kinda expensive to do all the time
//tty->print_cr("warning: slow verify happening");
//_phc._ifg->verify( &_phc );
return true;
}
// Conservative (but pessimistic) copy coalescing of a single block
void PhaseConservativeCoalesce::coalesce( Block *b ) {
// Bail out on infrequent blocks
if (_phc._cfg.is_uncommon(b)) {
return;
}
// Check this block for copies.
for( uint i = 1; i<b->end_idx(); i++ ) {
// Check for actual copies on inputs. Coalesce a copy into its
// input if use and copy's input are compatible.
Node *copy1 = b->get_node(i);
uint idx1 = copy1->is_Copy();
if( !idx1 ) continue; // Not a copy
if( copy_copy(copy1,copy1,b,i) ) {
i--; // Retry, same location in block
PhaseChaitin::_conserv_coalesce++; // Collect stats on success
continue;
}
}
}
Other Java examples (source code examples)Here is a short list of links related to this Java coalesce.cpp source code file: |
The search page
Other Java source code examples at this package level
Click here to learn more about this project
