1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/opto/coalesce.cpp Wed Apr 27 01:25:04 2016 +0800
1.3 @@ -0,0 +1,789 @@
1.4 +/*
1.5 + * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "precompiled.hpp"
1.29 +#include "memory/allocation.inline.hpp"
1.30 +#include "opto/block.hpp"
1.31 +#include "opto/cfgnode.hpp"
1.32 +#include "opto/chaitin.hpp"
1.33 +#include "opto/coalesce.hpp"
1.34 +#include "opto/connode.hpp"
1.35 +#include "opto/indexSet.hpp"
1.36 +#include "opto/machnode.hpp"
1.37 +#include "opto/matcher.hpp"
1.38 +#include "opto/regmask.hpp"
1.39 +
1.40 +#ifndef PRODUCT
1.41 +void PhaseCoalesce::dump(Node *n) const {
1.42 + // Being a const function means I cannot use 'Find'
1.43 + uint r = _phc._lrg_map.find(n);
1.44 + tty->print("L%d/N%d ",r,n->_idx);
1.45 +}
1.46 +
1.47 +void PhaseCoalesce::dump() const {
1.48 + // I know I have a block layout now, so I can print blocks in a loop
1.49 + for( uint i=0; i<_phc._cfg.number_of_blocks(); i++ ) {
1.50 + uint j;
1.51 + Block* b = _phc._cfg.get_block(i);
1.52 + // Print a nice block header
1.53 + tty->print("B%d: ",b->_pre_order);
1.54 + for( j=1; j<b->num_preds(); j++ )
1.55 + tty->print("B%d ", _phc._cfg.get_block_for_node(b->pred(j))->_pre_order);
1.56 + tty->print("-> ");
1.57 + for( j=0; j<b->_num_succs; j++ )
1.58 + tty->print("B%d ",b->_succs[j]->_pre_order);
1.59 + tty->print(" IDom: B%d/#%d\n", b->_idom ? b->_idom->_pre_order : 0, b->_dom_depth);
1.60 + uint cnt = b->number_of_nodes();
1.61 + for( j=0; j<cnt; j++ ) {
1.62 + Node *n = b->get_node(j);
1.63 + dump( n );
1.64 + tty->print("\t%s\t",n->Name());
1.65 +
1.66 + // Dump the inputs
1.67 + uint k; // Exit value of loop
1.68 + for( k=0; k<n->req(); k++ ) // For all required inputs
1.69 + if( n->in(k) ) dump( n->in(k) );
1.70 + else tty->print("_ ");
1.71 + int any_prec = 0;
1.72 + for( ; k<n->len(); k++ ) // For all precedence inputs
1.73 + if( n->in(k) ) {
1.74 + if( !any_prec++ ) tty->print(" |");
1.75 + dump( n->in(k) );
1.76 + }
1.77 +
1.78 + // Dump node-specific info
1.79 + n->dump_spec(tty);
1.80 + tty->print("\n");
1.81 +
1.82 + }
1.83 + tty->print("\n");
1.84 + }
1.85 +}
1.86 +#endif
1.87 +
1.88 +// Combine the live ranges def'd by these 2 Nodes. N2 is an input to N1.
1.89 +void PhaseCoalesce::combine_these_two(Node *n1, Node *n2) {
1.90 + uint lr1 = _phc._lrg_map.find(n1);
1.91 + uint lr2 = _phc._lrg_map.find(n2);
1.92 + if( lr1 != lr2 && // Different live ranges already AND
1.93 + !_phc._ifg->test_edge_sq( lr1, lr2 ) ) { // Do not interfere
1.94 + LRG *lrg1 = &_phc.lrgs(lr1);
1.95 + LRG *lrg2 = &_phc.lrgs(lr2);
1.96 + // Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
1.97 +
1.98 + // Now, why is int->oop OK? We end up declaring a raw-pointer as an oop
1.99 + // and in general that's a bad thing. However, int->oop conversions only
1.100 + // happen at GC points, so the lifetime of the misclassified raw-pointer
1.101 + // is from the CheckCastPP (that converts it to an oop) backwards up
1.102 + // through a merge point and into the slow-path call, and around the
1.103 + // diamond up to the heap-top check and back down into the slow-path call.
1.104 + // The misclassified raw pointer is NOT live across the slow-path call,
1.105 + // and so does not appear in any GC info, so the fact that it is
1.106 + // misclassified is OK.
1.107 +
1.108 + if( (lrg1->_is_oop || !lrg2->_is_oop) && // not an oop->int cast AND
1.109 + // Compatible final mask
1.110 + lrg1->mask().overlap( lrg2->mask() ) ) {
1.111 + // Merge larger into smaller.
1.112 + if( lr1 > lr2 ) {
1.113 + uint tmp = lr1; lr1 = lr2; lr2 = tmp;
1.114 + Node *n = n1; n1 = n2; n2 = n;
1.115 + LRG *ltmp = lrg1; lrg1 = lrg2; lrg2 = ltmp;
1.116 + }
1.117 + // Union lr2 into lr1
1.118 + _phc.Union( n1, n2 );
1.119 + if (lrg1->_maxfreq < lrg2->_maxfreq)
1.120 + lrg1->_maxfreq = lrg2->_maxfreq;
1.121 + // Merge in the IFG
1.122 + _phc._ifg->Union( lr1, lr2 );
1.123 + // Combine register restrictions
1.124 + lrg1->AND(lrg2->mask());
1.125 + }
1.126 + }
1.127 +}
1.128 +
1.129 +// Copy coalescing
1.130 +void PhaseCoalesce::coalesce_driver() {
1.131 + verify();
1.132 + // Coalesce from high frequency to low
1.133 + for (uint i = 0; i < _phc._cfg.number_of_blocks(); i++) {
1.134 + coalesce(_phc._blks[i]);
1.135 + }
1.136 +}
1.137 +
1.138 +// I am inserting copies to come out of SSA form. In the general case, I am
1.139 +// doing a parallel renaming. I'm in the Named world now, so I can't do a
1.140 +// general parallel renaming. All the copies now use "names" (live-ranges)
1.141 +// to carry values instead of the explicit use-def chains. Suppose I need to
1.142 +// insert 2 copies into the same block. They copy L161->L128 and L128->L132.
1.143 +// If I insert them in the wrong order then L128 will get clobbered before it
1.144 +// can get used by the second copy. This cannot happen in the SSA model;
1.145 +// direct use-def chains get me the right value. It DOES happen in the named
1.146 +// model so I have to handle the reordering of copies.
1.147 +//
1.148 +// In general, I need to topo-sort the placed copies to avoid conflicts.
1.149 +// Its possible to have a closed cycle of copies (e.g., recirculating the same
1.150 +// values around a loop). In this case I need a temp to break the cycle.
1.151 +void PhaseAggressiveCoalesce::insert_copy_with_overlap( Block *b, Node *copy, uint dst_name, uint src_name ) {
1.152 +
1.153 + // Scan backwards for the locations of the last use of the dst_name.
1.154 + // I am about to clobber the dst_name, so the copy must be inserted
1.155 + // after the last use. Last use is really first-use on a backwards scan.
1.156 + uint i = b->end_idx()-1;
1.157 + while(1) {
1.158 + Node *n = b->get_node(i);
1.159 + // Check for end of virtual copies; this is also the end of the
1.160 + // parallel renaming effort.
1.161 + if (n->_idx < _unique) {
1.162 + break;
1.163 + }
1.164 + uint idx = n->is_Copy();
1.165 + assert( idx || n->is_Con() || n->is_MachProj(), "Only copies during parallel renaming" );
1.166 + if (idx && _phc._lrg_map.find(n->in(idx)) == dst_name) {
1.167 + break;
1.168 + }
1.169 + i--;
1.170 + }
1.171 + uint last_use_idx = i;
1.172 +
1.173 + // Also search for any kill of src_name that exits the block.
1.174 + // Since the copy uses src_name, I have to come before any kill.
1.175 + uint kill_src_idx = b->end_idx();
1.176 + // There can be only 1 kill that exits any block and that is
1.177 + // the last kill. Thus it is the first kill on a backwards scan.
1.178 + i = b->end_idx()-1;
1.179 + while (1) {
1.180 + Node *n = b->get_node(i);
1.181 + // Check for end of virtual copies; this is also the end of the
1.182 + // parallel renaming effort.
1.183 + if (n->_idx < _unique) {
1.184 + break;
1.185 + }
1.186 + assert( n->is_Copy() || n->is_Con() || n->is_MachProj(), "Only copies during parallel renaming" );
1.187 + if (_phc._lrg_map.find(n) == src_name) {
1.188 + kill_src_idx = i;
1.189 + break;
1.190 + }
1.191 + i--;
1.192 + }
1.193 + // Need a temp? Last use of dst comes after the kill of src?
1.194 + if (last_use_idx >= kill_src_idx) {
1.195 + // Need to break a cycle with a temp
1.196 + uint idx = copy->is_Copy();
1.197 + Node *tmp = copy->clone();
1.198 + uint max_lrg_id = _phc._lrg_map.max_lrg_id();
1.199 + _phc.new_lrg(tmp, max_lrg_id);
1.200 + _phc._lrg_map.set_max_lrg_id(max_lrg_id + 1);
1.201 +
1.202 + // Insert new temp between copy and source
1.203 + tmp ->set_req(idx,copy->in(idx));
1.204 + copy->set_req(idx,tmp);
1.205 + // Save source in temp early, before source is killed
1.206 + b->insert_node(tmp, kill_src_idx);
1.207 + _phc._cfg.map_node_to_block(tmp, b);
1.208 + last_use_idx++;
1.209 + }
1.210 +
1.211 + // Insert just after last use
1.212 + b->insert_node(copy, last_use_idx + 1);
1.213 +}
1.214 +
1.215 +void PhaseAggressiveCoalesce::insert_copies( Matcher &matcher ) {
1.216 + // We do LRGs compressing and fix a liveout data only here since the other
1.217 + // place in Split() is guarded by the assert which we never hit.
1.218 + _phc._lrg_map.compress_uf_map_for_nodes();
1.219 + // Fix block's liveout data for compressed live ranges.
1.220 + for (uint lrg = 1; lrg < _phc._lrg_map.max_lrg_id(); lrg++) {
1.221 + uint compressed_lrg = _phc._lrg_map.find(lrg);
1.222 + if (lrg != compressed_lrg) {
1.223 + for (uint bidx = 0; bidx < _phc._cfg.number_of_blocks(); bidx++) {
1.224 + IndexSet *liveout = _phc._live->live(_phc._cfg.get_block(bidx));
1.225 + if (liveout->member(lrg)) {
1.226 + liveout->remove(lrg);
1.227 + liveout->insert(compressed_lrg);
1.228 + }
1.229 + }
1.230 + }
1.231 + }
1.232 +
1.233 + // All new nodes added are actual copies to replace virtual copies.
1.234 + // Nodes with index less than '_unique' are original, non-virtual Nodes.
1.235 + _unique = C->unique();
1.236 +
1.237 + for (uint i = 0; i < _phc._cfg.number_of_blocks(); i++) {
1.238 + C->check_node_count(NodeLimitFudgeFactor, "out of nodes in coalesce");
1.239 + if (C->failing()) return;
1.240 + Block *b = _phc._cfg.get_block(i);
1.241 + uint cnt = b->num_preds(); // Number of inputs to the Phi
1.242 +
1.243 + for( uint l = 1; l<b->number_of_nodes(); l++ ) {
1.244 + Node *n = b->get_node(l);
1.245 +
1.246 + // Do not use removed-copies, use copied value instead
1.247 + uint ncnt = n->req();
1.248 + for( uint k = 1; k<ncnt; k++ ) {
1.249 + Node *copy = n->in(k);
1.250 + uint cidx = copy->is_Copy();
1.251 + if( cidx ) {
1.252 + Node *def = copy->in(cidx);
1.253 + if (_phc._lrg_map.find(copy) == _phc._lrg_map.find(def)) {
1.254 + n->set_req(k, def);
1.255 + }
1.256 + }
1.257 + }
1.258 +
1.259 + // Remove any explicit copies that get coalesced.
1.260 + uint cidx = n->is_Copy();
1.261 + if( cidx ) {
1.262 + Node *def = n->in(cidx);
1.263 + if (_phc._lrg_map.find(n) == _phc._lrg_map.find(def)) {
1.264 + n->replace_by(def);
1.265 + n->set_req(cidx,NULL);
1.266 + b->remove_node(l);
1.267 + l--;
1.268 + continue;
1.269 + }
1.270 + }
1.271 +
1.272 + if (n->is_Phi()) {
1.273 + // Get the chosen name for the Phi
1.274 + uint phi_name = _phc._lrg_map.find(n);
1.275 + // Ignore the pre-allocated specials
1.276 + if (!phi_name) {
1.277 + continue;
1.278 + }
1.279 + // Check for mismatch inputs to Phi
1.280 + for (uint j = 1; j < cnt; j++) {
1.281 + Node *m = n->in(j);
1.282 + uint src_name = _phc._lrg_map.find(m);
1.283 + if (src_name != phi_name) {
1.284 + Block *pred = _phc._cfg.get_block_for_node(b->pred(j));
1.285 + Node *copy;
1.286 + assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
1.287 + // Rematerialize constants instead of copying them
1.288 + if( m->is_Mach() && m->as_Mach()->is_Con() &&
1.289 + m->as_Mach()->rematerialize() ) {
1.290 + copy = m->clone();
1.291 + // Insert the copy in the predecessor basic block
1.292 + pred->add_inst(copy);
1.293 + // Copy any flags as well
1.294 + _phc.clone_projs(pred, pred->end_idx(), m, copy, _phc._lrg_map);
1.295 + } else {
1.296 + const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
1.297 + copy = new (C) MachSpillCopyNode(m, *rm, *rm);
1.298 + // Find a good place to insert. Kinda tricky, use a subroutine
1.299 + insert_copy_with_overlap(pred,copy,phi_name,src_name);
1.300 + }
1.301 + // Insert the copy in the use-def chain
1.302 + n->set_req(j, copy);
1.303 + _phc._cfg.map_node_to_block(copy, pred);
1.304 + // Extend ("register allocate") the names array for the copy.
1.305 + _phc._lrg_map.extend(copy->_idx, phi_name);
1.306 + } // End of if Phi names do not match
1.307 + } // End of for all inputs to Phi
1.308 + } else { // End of if Phi
1.309 +
1.310 + // Now check for 2-address instructions
1.311 + uint idx;
1.312 + if( n->is_Mach() && (idx=n->as_Mach()->two_adr()) ) {
1.313 + // Get the chosen name for the Node
1.314 + uint name = _phc._lrg_map.find(n);
1.315 + assert (name, "no 2-address specials");
1.316 + // Check for name mis-match on the 2-address input
1.317 + Node *m = n->in(idx);
1.318 + if (_phc._lrg_map.find(m) != name) {
1.319 + Node *copy;
1.320 + assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
1.321 + // At this point it is unsafe to extend live ranges (6550579).
1.322 + // Rematerialize only constants as we do for Phi above.
1.323 + if(m->is_Mach() && m->as_Mach()->is_Con() &&
1.324 + m->as_Mach()->rematerialize()) {
1.325 + copy = m->clone();
1.326 + // Insert the copy in the basic block, just before us
1.327 + b->insert_node(copy, l++);
1.328 + l += _phc.clone_projs(b, l, m, copy, _phc._lrg_map);
1.329 + } else {
1.330 + const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
1.331 + copy = new (C) MachSpillCopyNode(m, *rm, *rm);
1.332 + // Insert the copy in the basic block, just before us
1.333 + b->insert_node(copy, l++);
1.334 + }
1.335 + // Insert the copy in the use-def chain
1.336 + n->set_req(idx, copy);
1.337 + // Extend ("register allocate") the names array for the copy.
1.338 + _phc._lrg_map.extend(copy->_idx, name);
1.339 + _phc._cfg.map_node_to_block(copy, b);
1.340 + }
1.341 +
1.342 + } // End of is two-adr
1.343 +
1.344 + // Insert a copy at a debug use for a lrg which has high frequency
1.345 + if (b->_freq < OPTO_DEBUG_SPLIT_FREQ || _phc._cfg.is_uncommon(b)) {
1.346 + // Walk the debug inputs to the node and check for lrg freq
1.347 + JVMState* jvms = n->jvms();
1.348 + uint debug_start = jvms ? jvms->debug_start() : 999999;
1.349 + uint debug_end = jvms ? jvms->debug_end() : 999999;
1.350 + for(uint inpidx = debug_start; inpidx < debug_end; inpidx++) {
1.351 + // Do not split monitors; they are only needed for debug table
1.352 + // entries and need no code.
1.353 + if (jvms->is_monitor_use(inpidx)) {
1.354 + continue;
1.355 + }
1.356 + Node *inp = n->in(inpidx);
1.357 + uint nidx = _phc._lrg_map.live_range_id(inp);
1.358 + LRG &lrg = lrgs(nidx);
1.359 +
1.360 + // If this lrg has a high frequency use/def
1.361 + if( lrg._maxfreq >= _phc.high_frequency_lrg() ) {
1.362 + // If the live range is also live out of this block (like it
1.363 + // would be for a fast/slow idiom), the normal spill mechanism
1.364 + // does an excellent job. If it is not live out of this block
1.365 + // (like it would be for debug info to uncommon trap) splitting
1.366 + // the live range now allows a better allocation in the high
1.367 + // frequency blocks.
1.368 + // Build_IFG_virtual has converted the live sets to
1.369 + // live-IN info, not live-OUT info.
1.370 + uint k;
1.371 + for( k=0; k < b->_num_succs; k++ )
1.372 + if( _phc._live->live(b->_succs[k])->member( nidx ) )
1.373 + break; // Live in to some successor block?
1.374 + if( k < b->_num_succs )
1.375 + continue; // Live out; do not pre-split
1.376 + // Split the lrg at this use
1.377 + const RegMask *rm = C->matcher()->idealreg2spillmask[inp->ideal_reg()];
1.378 + Node *copy = new (C) MachSpillCopyNode( inp, *rm, *rm );
1.379 + // Insert the copy in the use-def chain
1.380 + n->set_req(inpidx, copy );
1.381 + // Insert the copy in the basic block, just before us
1.382 + b->insert_node(copy, l++);
1.383 + // Extend ("register allocate") the names array for the copy.
1.384 + uint max_lrg_id = _phc._lrg_map.max_lrg_id();
1.385 + _phc.new_lrg(copy, max_lrg_id);
1.386 + _phc._lrg_map.set_max_lrg_id(max_lrg_id + 1);
1.387 + _phc._cfg.map_node_to_block(copy, b);
1.388 + //tty->print_cr("Split a debug use in Aggressive Coalesce");
1.389 + } // End of if high frequency use/def
1.390 + } // End of for all debug inputs
1.391 + } // End of if low frequency safepoint
1.392 +
1.393 + } // End of if Phi
1.394 +
1.395 + } // End of for all instructions
1.396 + } // End of for all blocks
1.397 +}
1.398 +
1.399 +
1.400 +// Aggressive (but pessimistic) copy coalescing of a single block
1.401 +
1.402 +// The following coalesce pass represents a single round of aggressive
1.403 +// pessimistic coalesce. "Aggressive" means no attempt to preserve
1.404 +// colorability when coalescing. This occasionally means more spills, but
1.405 +// it also means fewer rounds of coalescing for better code - and that means
1.406 +// faster compiles.
1.407 +
1.408 +// "Pessimistic" means we do not hit the fixed point in one pass (and we are
1.409 +// reaching for the least fixed point to boot). This is typically solved
1.410 +// with a few more rounds of coalescing, but the compiler must run fast. We
1.411 +// could optimistically coalescing everything touching PhiNodes together
1.412 +// into one big live range, then check for self-interference. Everywhere
1.413 +// the live range interferes with self it would have to be split. Finding
1.414 +// the right split points can be done with some heuristics (based on
1.415 +// expected frequency of edges in the live range). In short, it's a real
1.416 +// research problem and the timeline is too short to allow such research.
1.417 +// Further thoughts: (1) build the LR in a pass, (2) find self-interference
1.418 +// in another pass, (3) per each self-conflict, split, (4) split by finding
1.419 +// the low-cost cut (min-cut) of the LR, (5) edges in the LR are weighted
1.420 +// according to the GCM algorithm (or just exec freq on CFG edges).
1.421 +
1.422 +void PhaseAggressiveCoalesce::coalesce( Block *b ) {
1.423 + // Copies are still "virtual" - meaning we have not made them explicitly
1.424 + // copies. Instead, Phi functions of successor blocks have mis-matched
1.425 + // live-ranges. If I fail to coalesce, I'll have to insert a copy to line
1.426 + // up the live-ranges. Check for Phis in successor blocks.
1.427 + uint i;
1.428 + for( i=0; i<b->_num_succs; i++ ) {
1.429 + Block *bs = b->_succs[i];
1.430 + // Find index of 'b' in 'bs' predecessors
1.431 + uint j=1;
1.432 + while (_phc._cfg.get_block_for_node(bs->pred(j)) != b) {
1.433 + j++;
1.434 + }
1.435 +
1.436 + // Visit all the Phis in successor block
1.437 + for( uint k = 1; k<bs->number_of_nodes(); k++ ) {
1.438 + Node *n = bs->get_node(k);
1.439 + if( !n->is_Phi() ) break;
1.440 + combine_these_two( n, n->in(j) );
1.441 + }
1.442 + } // End of for all successor blocks
1.443 +
1.444 +
1.445 + // Check _this_ block for 2-address instructions and copies.
1.446 + uint cnt = b->end_idx();
1.447 + for( i = 1; i<cnt; i++ ) {
1.448 + Node *n = b->get_node(i);
1.449 + uint idx;
1.450 + // 2-address instructions have a virtual Copy matching their input
1.451 + // to their output
1.452 + if (n->is_Mach() && (idx = n->as_Mach()->two_adr())) {
1.453 + MachNode *mach = n->as_Mach();
1.454 + combine_these_two(mach, mach->in(idx));
1.455 + }
1.456 + } // End of for all instructions in block
1.457 +}
1.458 +
1.459 +PhaseConservativeCoalesce::PhaseConservativeCoalesce(PhaseChaitin &chaitin) : PhaseCoalesce(chaitin) {
1.460 + _ulr.initialize(_phc._lrg_map.max_lrg_id());
1.461 +}
1.462 +
1.463 +void PhaseConservativeCoalesce::verify() {
1.464 +#ifdef ASSERT
1.465 + _phc.set_was_low();
1.466 +#endif
1.467 +}
1.468 +
1.469 +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 ) {
1.470 + // Join live ranges. Merge larger into smaller. Union lr2 into lr1 in the
1.471 + // union-find tree
1.472 + _phc.Union( lr1_node, lr2_node );
1.473 +
1.474 + // Single-def live range ONLY if both live ranges are single-def.
1.475 + // If both are single def, then src_def powers one live range
1.476 + // and def_copy powers the other. After merging, src_def powers
1.477 + // the combined live range.
1.478 + lrgs(lr1)._def = (lrgs(lr1).is_multidef() ||
1.479 + lrgs(lr2).is_multidef() )
1.480 + ? NodeSentinel : src_def;
1.481 + lrgs(lr2)._def = NULL; // No def for lrg 2
1.482 + lrgs(lr2).Clear(); // Force empty mask for LRG 2
1.483 + //lrgs(lr2)._size = 0; // Live-range 2 goes dead
1.484 + lrgs(lr1)._is_oop |= lrgs(lr2)._is_oop;
1.485 + lrgs(lr2)._is_oop = 0; // In particular, not an oop for GC info
1.486 +
1.487 + if (lrgs(lr1)._maxfreq < lrgs(lr2)._maxfreq)
1.488 + lrgs(lr1)._maxfreq = lrgs(lr2)._maxfreq;
1.489 +
1.490 + // Copy original value instead. Intermediate copies go dead, and
1.491 + // the dst_copy becomes useless.
1.492 + int didx = dst_copy->is_Copy();
1.493 + dst_copy->set_req( didx, src_def );
1.494 + // Add copy to free list
1.495 + // _phc.free_spillcopy(b->_nodes[bindex]);
1.496 + assert( b->get_node(bindex) == dst_copy, "" );
1.497 + dst_copy->replace_by( dst_copy->in(didx) );
1.498 + dst_copy->set_req( didx, NULL);
1.499 + b->remove_node(bindex);
1.500 + if( bindex < b->_ihrp_index ) b->_ihrp_index--;
1.501 + if( bindex < b->_fhrp_index ) b->_fhrp_index--;
1.502 +
1.503 + // Stretched lr1; add it to liveness of intermediate blocks
1.504 + Block *b2 = _phc._cfg.get_block_for_node(src_copy);
1.505 + while( b != b2 ) {
1.506 + b = _phc._cfg.get_block_for_node(b->pred(1));
1.507 + _phc._live->live(b)->insert(lr1);
1.508 + }
1.509 +}
1.510 +
1.511 +// Factored code from copy_copy that computes extra interferences from
1.512 +// lengthening a live range by double-coalescing.
1.513 +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 ) {
1.514 +
1.515 + assert(!lrgs(lr1)._fat_proj, "cannot coalesce fat_proj");
1.516 + assert(!lrgs(lr2)._fat_proj, "cannot coalesce fat_proj");
1.517 + Node *prev_copy = dst_copy->in(dst_copy->is_Copy());
1.518 + Block *b2 = b;
1.519 + uint bindex2 = bindex;
1.520 + while( 1 ) {
1.521 + // Find previous instruction
1.522 + bindex2--; // Chain backwards 1 instruction
1.523 + while( bindex2 == 0 ) { // At block start, find prior block
1.524 + assert( b2->num_preds() == 2, "cannot double coalesce across c-flow" );
1.525 + b2 = _phc._cfg.get_block_for_node(b2->pred(1));
1.526 + bindex2 = b2->end_idx()-1;
1.527 + }
1.528 + // Get prior instruction
1.529 + assert(bindex2 < b2->number_of_nodes(), "index out of bounds");
1.530 + Node *x = b2->get_node(bindex2);
1.531 + if( x == prev_copy ) { // Previous copy in copy chain?
1.532 + if( prev_copy == src_copy)// Found end of chain and all interferences
1.533 + break; // So break out of loop
1.534 + // Else work back one in copy chain
1.535 + prev_copy = prev_copy->in(prev_copy->is_Copy());
1.536 + } else { // Else collect interferences
1.537 + uint lidx = _phc._lrg_map.find(x);
1.538 + // Found another def of live-range being stretched?
1.539 + if(lidx == lr1) {
1.540 + return max_juint;
1.541 + }
1.542 + if(lidx == lr2) {
1.543 + return max_juint;
1.544 + }
1.545 +
1.546 + // If we attempt to coalesce across a bound def
1.547 + if( lrgs(lidx).is_bound() ) {
1.548 + // Do not let the coalesced LRG expect to get the bound color
1.549 + rm.SUBTRACT( lrgs(lidx).mask() );
1.550 + // Recompute rm_size
1.551 + rm_size = rm.Size();
1.552 + //if( rm._flags ) rm_size += 1000000;
1.553 + if( reg_degree >= rm_size ) return max_juint;
1.554 + }
1.555 + if( rm.overlap(lrgs(lidx).mask()) ) {
1.556 + // Insert lidx into union LRG; returns TRUE if actually inserted
1.557 + if( _ulr.insert(lidx) ) {
1.558 + // Infinite-stack neighbors do not alter colorability, as they
1.559 + // can always color to some other color.
1.560 + if( !lrgs(lidx).mask().is_AllStack() ) {
1.561 + // If this coalesce will make any new neighbor uncolorable,
1.562 + // do not coalesce.
1.563 + if( lrgs(lidx).just_lo_degree() )
1.564 + return max_juint;
1.565 + // Bump our degree
1.566 + if( ++reg_degree >= rm_size )
1.567 + return max_juint;
1.568 + } // End of if not infinite-stack neighbor
1.569 + } // End of if actually inserted
1.570 + } // End of if live range overlaps
1.571 + } // End of else collect interferences for 1 node
1.572 + } // End of while forever, scan back for interferences
1.573 + return reg_degree;
1.574 +}
1.575 +
1.576 +void PhaseConservativeCoalesce::update_ifg(uint lr1, uint lr2, IndexSet *n_lr1, IndexSet *n_lr2) {
1.577 + // Some original neighbors of lr1 might have gone away
1.578 + // because the constrained register mask prevented them.
1.579 + // Remove lr1 from such neighbors.
1.580 + IndexSetIterator one(n_lr1);
1.581 + uint neighbor;
1.582 + LRG &lrg1 = lrgs(lr1);
1.583 + while ((neighbor = one.next()) != 0)
1.584 + if( !_ulr.member(neighbor) )
1.585 + if( _phc._ifg->neighbors(neighbor)->remove(lr1) )
1.586 + lrgs(neighbor).inc_degree( -lrg1.compute_degree(lrgs(neighbor)) );
1.587 +
1.588 +
1.589 + // lr2 is now called (coalesced into) lr1.
1.590 + // Remove lr2 from the IFG.
1.591 + IndexSetIterator two(n_lr2);
1.592 + LRG &lrg2 = lrgs(lr2);
1.593 + while ((neighbor = two.next()) != 0)
1.594 + if( _phc._ifg->neighbors(neighbor)->remove(lr2) )
1.595 + lrgs(neighbor).inc_degree( -lrg2.compute_degree(lrgs(neighbor)) );
1.596 +
1.597 + // Some neighbors of intermediate copies now interfere with the
1.598 + // combined live range.
1.599 + IndexSetIterator three(&_ulr);
1.600 + while ((neighbor = three.next()) != 0)
1.601 + if( _phc._ifg->neighbors(neighbor)->insert(lr1) )
1.602 + lrgs(neighbor).inc_degree( lrg1.compute_degree(lrgs(neighbor)) );
1.603 +}
1.604 +
1.605 +static void record_bias( const PhaseIFG *ifg, int lr1, int lr2 ) {
1.606 + // Tag copy bias here
1.607 + if( !ifg->lrgs(lr1)._copy_bias )
1.608 + ifg->lrgs(lr1)._copy_bias = lr2;
1.609 + if( !ifg->lrgs(lr2)._copy_bias )
1.610 + ifg->lrgs(lr2)._copy_bias = lr1;
1.611 +}
1.612 +
1.613 +// See if I can coalesce a series of multiple copies together. I need the
1.614 +// final dest copy and the original src copy. They can be the same Node.
1.615 +// Compute the compatible register masks.
1.616 +bool PhaseConservativeCoalesce::copy_copy(Node *dst_copy, Node *src_copy, Block *b, uint bindex) {
1.617 +
1.618 + if (!dst_copy->is_SpillCopy()) {
1.619 + return false;
1.620 + }
1.621 + if (!src_copy->is_SpillCopy()) {
1.622 + return false;
1.623 + }
1.624 + Node *src_def = src_copy->in(src_copy->is_Copy());
1.625 + uint lr1 = _phc._lrg_map.find(dst_copy);
1.626 + uint lr2 = _phc._lrg_map.find(src_def);
1.627 +
1.628 + // Same live ranges already?
1.629 + if (lr1 == lr2) {
1.630 + return false;
1.631 + }
1.632 +
1.633 + // Interfere?
1.634 + if (_phc._ifg->test_edge_sq(lr1, lr2)) {
1.635 + return false;
1.636 + }
1.637 +
1.638 + // Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
1.639 + if (!lrgs(lr1)._is_oop && lrgs(lr2)._is_oop) { // not an oop->int cast
1.640 + return false;
1.641 + }
1.642 +
1.643 + // Coalescing between an aligned live range and a mis-aligned live range?
1.644 + // No, no! Alignment changes how we count degree.
1.645 + if (lrgs(lr1)._fat_proj != lrgs(lr2)._fat_proj) {
1.646 + return false;
1.647 + }
1.648 +
1.649 + // Sort; use smaller live-range number
1.650 + Node *lr1_node = dst_copy;
1.651 + Node *lr2_node = src_def;
1.652 + if (lr1 > lr2) {
1.653 + uint tmp = lr1; lr1 = lr2; lr2 = tmp;
1.654 + lr1_node = src_def; lr2_node = dst_copy;
1.655 + }
1.656 +
1.657 + // Check for compatibility of the 2 live ranges by
1.658 + // intersecting their allowed register sets.
1.659 + RegMask rm = lrgs(lr1).mask();
1.660 + rm.AND(lrgs(lr2).mask());
1.661 + // Number of bits free
1.662 + uint rm_size = rm.Size();
1.663 +
1.664 + if (UseFPUForSpilling && rm.is_AllStack() ) {
1.665 + // Don't coalesce when frequency difference is large
1.666 + Block *dst_b = _phc._cfg.get_block_for_node(dst_copy);
1.667 + Block *src_def_b = _phc._cfg.get_block_for_node(src_def);
1.668 + if (src_def_b->_freq > 10*dst_b->_freq )
1.669 + return false;
1.670 + }
1.671 +
1.672 + // If we can use any stack slot, then effective size is infinite
1.673 + if( rm.is_AllStack() ) rm_size += 1000000;
1.674 + // Incompatible masks, no way to coalesce
1.675 + if( rm_size == 0 ) return false;
1.676 +
1.677 + // Another early bail-out test is when we are double-coalescing and the
1.678 + // 2 copies are separated by some control flow.
1.679 + if( dst_copy != src_copy ) {
1.680 + Block *src_b = _phc._cfg.get_block_for_node(src_copy);
1.681 + Block *b2 = b;
1.682 + while( b2 != src_b ) {
1.683 + if( b2->num_preds() > 2 ){// Found merge-point
1.684 + _phc._lost_opp_cflow_coalesce++;
1.685 + // extra record_bias commented out because Chris believes it is not
1.686 + // productive. Since we can record only 1 bias, we want to choose one
1.687 + // that stands a chance of working and this one probably does not.
1.688 + //record_bias( _phc._lrgs, lr1, lr2 );
1.689 + return false; // To hard to find all interferences
1.690 + }
1.691 + b2 = _phc._cfg.get_block_for_node(b2->pred(1));
1.692 + }
1.693 + }
1.694 +
1.695 + // Union the two interference sets together into '_ulr'
1.696 + uint reg_degree = _ulr.lrg_union( lr1, lr2, rm_size, _phc._ifg, rm );
1.697 +
1.698 + if( reg_degree >= rm_size ) {
1.699 + record_bias( _phc._ifg, lr1, lr2 );
1.700 + return false;
1.701 + }
1.702 +
1.703 + // Now I need to compute all the interferences between dst_copy and
1.704 + // src_copy. I'm not willing visit the entire interference graph, so
1.705 + // I limit my search to things in dst_copy's block or in a straight
1.706 + // line of previous blocks. I give up at merge points or when I get
1.707 + // more interferences than my degree. I can stop when I find src_copy.
1.708 + if( dst_copy != src_copy ) {
1.709 + reg_degree = compute_separating_interferences(dst_copy, src_copy, b, bindex, rm, rm_size, reg_degree, lr1, lr2 );
1.710 + if( reg_degree == max_juint ) {
1.711 + record_bias( _phc._ifg, lr1, lr2 );
1.712 + return false;
1.713 + }
1.714 + } // End of if dst_copy & src_copy are different
1.715 +
1.716 +
1.717 + // ---- THE COMBINED LRG IS COLORABLE ----
1.718 +
1.719 + // YEAH - Now coalesce this copy away
1.720 + assert( lrgs(lr1).num_regs() == lrgs(lr2).num_regs(), "" );
1.721 +
1.722 + IndexSet *n_lr1 = _phc._ifg->neighbors(lr1);
1.723 + IndexSet *n_lr2 = _phc._ifg->neighbors(lr2);
1.724 +
1.725 + // Update the interference graph
1.726 + update_ifg(lr1, lr2, n_lr1, n_lr2);
1.727 +
1.728 + _ulr.remove(lr1);
1.729 +
1.730 + // Uncomment the following code to trace Coalescing in great detail.
1.731 + //
1.732 + //if (false) {
1.733 + // tty->cr();
1.734 + // tty->print_cr("#######################################");
1.735 + // tty->print_cr("union %d and %d", lr1, lr2);
1.736 + // n_lr1->dump();
1.737 + // n_lr2->dump();
1.738 + // tty->print_cr("resulting set is");
1.739 + // _ulr.dump();
1.740 + //}
1.741 +
1.742 + // Replace n_lr1 with the new combined live range. _ulr will use
1.743 + // n_lr1's old memory on the next iteration. n_lr2 is cleared to
1.744 + // send its internal memory to the free list.
1.745 + _ulr.swap(n_lr1);
1.746 + _ulr.clear();
1.747 + n_lr2->clear();
1.748 +
1.749 + lrgs(lr1).set_degree( _phc._ifg->effective_degree(lr1) );
1.750 + lrgs(lr2).set_degree( 0 );
1.751 +
1.752 + // Join live ranges. Merge larger into smaller. Union lr2 into lr1 in the
1.753 + // union-find tree
1.754 + union_helper( lr1_node, lr2_node, lr1, lr2, src_def, dst_copy, src_copy, b, bindex );
1.755 + // Combine register restrictions
1.756 + lrgs(lr1).set_mask(rm);
1.757 + lrgs(lr1).compute_set_mask_size();
1.758 + lrgs(lr1)._cost += lrgs(lr2)._cost;
1.759 + lrgs(lr1)._area += lrgs(lr2)._area;
1.760 +
1.761 + // While its uncommon to successfully coalesce live ranges that started out
1.762 + // being not-lo-degree, it can happen. In any case the combined coalesced
1.763 + // live range better Simplify nicely.
1.764 + lrgs(lr1)._was_lo = 1;
1.765 +
1.766 + // kinda expensive to do all the time
1.767 + //tty->print_cr("warning: slow verify happening");
1.768 + //_phc._ifg->verify( &_phc );
1.769 + return true;
1.770 +}
1.771 +
1.772 +// Conservative (but pessimistic) copy coalescing of a single block
1.773 +void PhaseConservativeCoalesce::coalesce( Block *b ) {
1.774 + // Bail out on infrequent blocks
1.775 + if (_phc._cfg.is_uncommon(b)) {
1.776 + return;
1.777 + }
1.778 + // Check this block for copies.
1.779 + for( uint i = 1; i<b->end_idx(); i++ ) {
1.780 + // Check for actual copies on inputs. Coalesce a copy into its
1.781 + // input if use and copy's input are compatible.
1.782 + Node *copy1 = b->get_node(i);
1.783 + uint idx1 = copy1->is_Copy();
1.784 + if( !idx1 ) continue; // Not a copy
1.785 +
1.786 + if( copy_copy(copy1,copy1,b,i) ) {
1.787 + i--; // Retry, same location in block
1.788 + PhaseChaitin::_conserv_coalesce++; // Collect stats on success
1.789 + continue;
1.790 + }
1.791 + }
1.792 +}
