/* * Copyright (c) 1997, 2012, 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 "libadt/vectset.hpp" #include "memory/allocation.inline.hpp" #include "opto/block.hpp" #include "opto/cfgnode.hpp" #include "opto/chaitin.hpp" #include "opto/loopnode.hpp" #include "opto/machnode.hpp" #include "opto/matcher.hpp" #include "opto/opcodes.hpp" #include "opto/rootnode.hpp" #include "utilities/copy.hpp" // Optimization - Graph Style //----------------------------------------------------------------------------- void Block_Array::grow( uint i ) { assert(i >= Max(), "must be an overflow"); debug_only(_limit = i+1); if( i < _size ) return; if( !_size ) { _size = 1; _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) ); _blocks[0] = NULL; } uint old = _size; while( i >= _size ) _size <<= 1; // Double to fit _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*)); Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) ); } //============================================================================= void Block_List::remove(uint i) { assert(i < _cnt, "index out of bounds"); Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*))); pop(); // shrink list by one block } void Block_List::insert(uint i, Block *b) { push(b); // grow list by one block Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*))); _blocks[i] = b; } #ifndef PRODUCT void Block_List::print() { for (uint i=0; i < size(); i++) { tty->print("B%d ", _blocks[i]->_pre_order); } tty->print("size = %d\n", size()); } #endif //============================================================================= uint Block::code_alignment() { // Check for Root block if (_pre_order == 0) return CodeEntryAlignment; // Check for Start block if (_pre_order == 1) return InteriorEntryAlignment; // Check for loop alignment if (has_loop_alignment()) return loop_alignment(); return relocInfo::addr_unit(); // no particular alignment } uint Block::compute_loop_alignment() { Node *h = head(); int unit_sz = relocInfo::addr_unit(); if (h->is_Loop() && h->as_Loop()->is_inner_loop()) { // Pre- and post-loops have low trip count so do not bother with // NOPs for align loop head. The constants are hidden from tuning // but only because my "divide by 4" heuristic surely gets nearly // all possible gain (a "do not align at all" heuristic has a // chance of getting a really tiny gain). if (h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() || h->as_CountedLoop()->is_post_loop())) { return (OptoLoopAlignment > 4*unit_sz) ? (OptoLoopAlignment>>2) : unit_sz; } // Loops with low backedge frequency should not be aligned. Node *n = h->in(LoopNode::LoopBackControl)->in(0); if (n->is_MachIf() && n->as_MachIf()->_prob < 0.01) { return unit_sz; // Loop does not loop, more often than not! } return OptoLoopAlignment; // Otherwise align loop head } return unit_sz; // no particular alignment } //----------------------------------------------------------------------------- // Compute the size of first 'inst_cnt' instructions in this block. // Return the number of instructions left to compute if the block has // less then 'inst_cnt' instructions. Stop, and return 0 if sum_size // exceeds OptoLoopAlignment. uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra) { uint last_inst = _nodes.size(); for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) { uint inst_size = _nodes[j]->size(ra); if( inst_size > 0 ) { inst_cnt--; uint sz = sum_size + inst_size; if( sz <= (uint)OptoLoopAlignment ) { // Compute size of instructions which fit into fetch buffer only // since all inst_cnt instructions will not fit even if we align them. sum_size = sz; } else { return 0; } } } return inst_cnt; } //----------------------------------------------------------------------------- uint Block::find_node( const Node *n ) const { for( uint i = 0; i < _nodes.size(); i++ ) { if( _nodes[i] == n ) return i; } ShouldNotReachHere(); return 0; } // Find and remove n from block list void Block::find_remove( const Node *n ) { _nodes.remove(find_node(n)); } //------------------------------is_Empty--------------------------------------- // Return empty status of a block. Empty blocks contain only the head, other // ideal nodes, and an optional trailing goto. int Block::is_Empty() const { // Root or start block is not considered empty if (head()->is_Root() || head()->is_Start()) { return not_empty; } int success_result = completely_empty; int end_idx = _nodes.size()-1; // Check for ending goto if ((end_idx > 0) && (_nodes[end_idx]->is_MachGoto())) { success_result = empty_with_goto; end_idx--; } // Unreachable blocks are considered empty if (num_preds() <= 1) { return success_result; } // Ideal nodes are allowable in empty blocks: skip them Only MachNodes // turn directly into code, because only MachNodes have non-trivial // emit() functions. while ((end_idx > 0) && !_nodes[end_idx]->is_Mach()) { end_idx--; } // No room for any interesting instructions? if (end_idx == 0) { return success_result; } return not_empty; } //------------------------------has_uncommon_code------------------------------ // Return true if the block's code implies that it is likely to be // executed infrequently. Check to see if the block ends in a Halt or // a low probability call. bool Block::has_uncommon_code() const { Node* en = end(); if (en->is_MachGoto()) en = en->in(0); if (en->is_Catch()) en = en->in(0); if (en->is_MachProj() && en->in(0)->is_MachCall()) { MachCallNode* call = en->in(0)->as_MachCall(); if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) { // This is true for slow-path stubs like new_{instance,array}, // slow_arraycopy, complete_monitor_locking, uncommon_trap. // The magic number corresponds to the probability of an uncommon_trap, // even though it is a count not a probability. return true; } } int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode(); return op == Op_Halt; } //------------------------------is_uncommon------------------------------------ // True if block is low enough frequency or guarded by a test which // mostly does not go here. bool Block::is_uncommon( Block_Array &bbs ) const { // Initial blocks must never be moved, so are never uncommon. if (head()->is_Root() || head()->is_Start()) return false; // Check for way-low freq if( _freq < BLOCK_FREQUENCY(0.00001f) ) return true; // Look for code shape indicating uncommon_trap or slow path if (has_uncommon_code()) return true; const float epsilon = 0.05f; const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon); uint uncommon_preds = 0; uint freq_preds = 0; uint uncommon_for_freq_preds = 0; for( uint i=1; i_idx]; // Check to see if this block follows its guard 1 time out of 10000 // or less. // // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which // we intend to be "uncommon", such as slow-path TLE allocation, // predicted call failure, and uncommon trap triggers. // // Use an epsilon value of 5% to allow for variability in frequency // predictions and floating point calculations. The net effect is // that guard_factor is set to 9500. // // Ignore low-frequency blocks. // The next check is (guard->_freq < 1.e-5 * 9500.). if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) { uncommon_preds++; } else { freq_preds++; if( _freq < guard->_freq * guard_factor ) { uncommon_for_freq_preds++; } } } if( num_preds() > 1 && // The block is uncommon if all preds are uncommon or (uncommon_preds == (num_preds()-1) || // it is uncommon for all frequent preds. uncommon_for_freq_preds == freq_preds) ) { return true; } return false; } //------------------------------dump------------------------------------------- #ifndef PRODUCT void Block::dump_bidx(const Block* orig, outputStream* st) const { if (_pre_order) st->print("B%d",_pre_order); else st->print("N%d", head()->_idx); if (Verbose && orig != this) { // Dump the original block's idx st->print(" ("); orig->dump_bidx(orig, st); st->print(")"); } } void Block::dump_pred(const Block_Array *bbs, Block* orig, outputStream* st) const { if (is_connector()) { for (uint i=1; i_idx]); p->dump_pred(bbs, orig, st); } } else { dump_bidx(orig, st); st->print(" "); } } void Block::dump_head( const Block_Array *bbs, outputStream* st ) const { // Print the basic block dump_bidx(this, st); st->print(": #\t"); // Print the incoming CFG edges and the outgoing CFG edges for( uint i=0; i<_num_succs; i++ ) { non_connector_successor(i)->dump_bidx(_succs[i], st); st->print(" "); } st->print("<- "); if( head()->is_block_start() ) { for (uint i=1; i_idx]; p->dump_pred(bbs, p, st); } else { while (!s->is_block_start()) s = s->in(0); st->print("N%d ", s->_idx ); } } } else st->print("BLOCK HEAD IS JUNK "); // Print loop, if any const Block *bhead = this; // Head of self-loop Node *bh = bhead->head(); if( bbs && bh->is_Loop() && !head()->is_Root() ) { LoopNode *loop = bh->as_Loop(); const Block *bx = (*bbs)[loop->in(LoopNode::LoopBackControl)->_idx]; while (bx->is_connector()) { bx = (*bbs)[bx->pred(1)->_idx]; } st->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order); // Dump any loop-specific bits, especially for CountedLoops. loop->dump_spec(st); } else if (has_loop_alignment()) { st->print(" top-of-loop"); } st->print(" Freq: %g",_freq); if( Verbose || WizardMode ) { st->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth); st->print(" RegPressure: %d",_reg_pressure); st->print(" IHRP Index: %d",_ihrp_index); st->print(" FRegPressure: %d",_freg_pressure); st->print(" FHRP Index: %d",_fhrp_index); } st->print_cr(""); } void Block::dump() const { dump(NULL); } void Block::dump( const Block_Array *bbs ) const { dump_head(bbs); uint cnt = _nodes.size(); for( uint i=0; idump(); tty->print("\n"); } #endif //============================================================================= //------------------------------PhaseCFG--------------------------------------- PhaseCFG::PhaseCFG( Arena *a, RootNode *r, Matcher &m ) : Phase(CFG), _bbs(a), _root(r), _node_latency(NULL) #ifndef PRODUCT , _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining")) #endif #ifdef ASSERT , _raw_oops(a) #endif { ResourceMark rm; // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode, // then Match it into a machine-specific Node. Then clone the machine // Node on demand. Node *x = new (C) GotoNode(NULL); x->init_req(0, x); _goto = m.match_tree(x); assert(_goto != NULL, ""); _goto->set_req(0,_goto); // Build the CFG in Reverse Post Order _num_blocks = build_cfg(); _broot = _bbs[_root->_idx]; } //------------------------------build_cfg-------------------------------------- // Build a proper looking CFG. Make every block begin with either a StartNode // or a RegionNode. Make every block end with either a Goto, If or Return. // The RootNode both starts and ends it's own block. Do this with a recursive // backwards walk over the control edges. uint PhaseCFG::build_cfg() { Arena *a = Thread::current()->resource_area(); VectorSet visited(a); // Allocate stack with enough space to avoid frequent realloc Node_Stack nstack(a, C->unique() >> 1); nstack.push(_root, 0); uint sum = 0; // Counter for blocks while (nstack.is_nonempty()) { // node and in's index from stack's top // 'np' is _root (see above) or RegionNode, StartNode: we push on stack // only nodes which point to the start of basic block (see below). Node *np = nstack.node(); // idx > 0, except for the first node (_root) pushed on stack // at the beginning when idx == 0. // We will use the condition (idx == 0) later to end the build. uint idx = nstack.index(); Node *proj = np->in(idx); const Node *x = proj->is_block_proj(); // Does the block end with a proper block-ending Node? One of Return, // If or Goto? (This check should be done for visited nodes also). if (x == NULL) { // Does not end right... Node *g = _goto->clone(); // Force it to end in a Goto g->set_req(0, proj); np->set_req(idx, g); x = proj = g; } if (!visited.test_set(x->_idx)) { // Visit this block once // Skip any control-pinned middle'in stuff Node *p = proj; do { proj = p; // Update pointer to last Control p = p->in(0); // Move control forward } while( !p->is_block_proj() && !p->is_block_start() ); // Make the block begin with one of Region or StartNode. if( !p->is_block_start() ) { RegionNode *r = new (C) RegionNode( 2 ); r->init_req(1, p); // Insert RegionNode in the way proj->set_req(0, r); // Insert RegionNode in the way p = r; } // 'p' now points to the start of this basic block // Put self in array of basic blocks Block *bb = new (_bbs._arena) Block(_bbs._arena,p); _bbs.map(p->_idx,bb); _bbs.map(x->_idx,bb); if( x != p ) { // Only for root is x == p bb->_nodes.push((Node*)x); } // Now handle predecessors ++sum; // Count 1 for self block uint cnt = bb->num_preds(); for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors Node *prevproj = p->in(i); // Get prior input assert( !prevproj->is_Con(), "dead input not removed" ); // Check to see if p->in(i) is a "control-dependent" CFG edge - // i.e., it splits at the source (via an IF or SWITCH) and merges // at the destination (via a many-input Region). // This breaks critical edges. The RegionNode to start the block // will be added when is pulled off the node stack if ( cnt > 2 ) { // Merging many things? assert( prevproj== bb->pred(i),""); if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge? // Force a block on the control-dependent edge Node *g = _goto->clone(); // Force it to end in a Goto g->set_req(0,prevproj); p->set_req(i,g); } } nstack.push(p, i); // 'p' is RegionNode or StartNode } } else { // Post-processing visited nodes nstack.pop(); // remove node from stack // Check if it the fist node pushed on stack at the beginning. if (idx == 0) break; // end of the build // Find predecessor basic block Block *pb = _bbs[x->_idx]; // Insert into nodes array, if not already there if( !_bbs.lookup(proj->_idx) ) { assert( x != proj, "" ); // Map basic block of projection _bbs.map(proj->_idx,pb); pb->_nodes.push(proj); } // Insert self as a child of my predecessor block pb->_succs.map(pb->_num_succs++, _bbs[np->_idx]); assert( pb->_nodes[ pb->_nodes.size() - pb->_num_succs ]->is_block_proj(), "too many control users, not a CFG?" ); } } // Return number of basic blocks for all children and self return sum; } //------------------------------insert_goto_at--------------------------------- // Inserts a goto & corresponding basic block between // block[block_no] and its succ_no'th successor block void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) { // get block with block_no assert(block_no < _num_blocks, "illegal block number"); Block* in = _blocks[block_no]; // get successor block succ_no assert(succ_no < in->_num_succs, "illegal successor number"); Block* out = in->_succs[succ_no]; // Compute frequency of the new block. Do this before inserting // new block in case succ_prob() needs to infer the probability from // surrounding blocks. float freq = in->_freq * in->succ_prob(succ_no); // get ProjNode corresponding to the succ_no'th successor of the in block ProjNode* proj = in->_nodes[in->_nodes.size() - in->_num_succs + succ_no]->as_Proj(); // create region for basic block RegionNode* region = new (C) RegionNode(2); region->init_req(1, proj); // setup corresponding basic block Block* block = new (_bbs._arena) Block(_bbs._arena, region); _bbs.map(region->_idx, block); C->regalloc()->set_bad(region->_idx); // add a goto node Node* gto = _goto->clone(); // get a new goto node gto->set_req(0, region); // add it to the basic block block->_nodes.push(gto); _bbs.map(gto->_idx, block); C->regalloc()->set_bad(gto->_idx); // hook up successor block block->_succs.map(block->_num_succs++, out); // remap successor's predecessors if necessary for (uint i = 1; i < out->num_preds(); i++) { if (out->pred(i) == proj) out->head()->set_req(i, gto); } // remap predecessor's successor to new block in->_succs.map(succ_no, block); // Set the frequency of the new block block->_freq = freq; // add new basic block to basic block list _blocks.insert(block_no + 1, block); _num_blocks++; } //------------------------------no_flip_branch--------------------------------- // Does this block end in a multiway branch that cannot have the default case // flipped for another case? static bool no_flip_branch( Block *b ) { int branch_idx = b->_nodes.size() - b->_num_succs-1; if( branch_idx < 1 ) return false; Node *bra = b->_nodes[branch_idx]; if( bra->is_Catch() ) return true; if( bra->is_Mach() ) { if( bra->is_MachNullCheck() ) return true; int iop = bra->as_Mach()->ideal_Opcode(); if( iop == Op_FastLock || iop == Op_FastUnlock ) return true; } return false; } //------------------------------convert_NeverBranch_to_Goto-------------------- // Check for NeverBranch at block end. This needs to become a GOTO to the // true target. NeverBranch are treated as a conditional branch that always // goes the same direction for most of the optimizer and are used to give a // fake exit path to infinite loops. At this late stage they need to turn // into Goto's so that when you enter the infinite loop you indeed hang. void PhaseCFG::convert_NeverBranch_to_Goto(Block *b) { // Find true target int end_idx = b->end_idx(); int idx = b->_nodes[end_idx+1]->as_Proj()->_con; Block *succ = b->_succs[idx]; Node* gto = _goto->clone(); // get a new goto node gto->set_req(0, b->head()); Node *bp = b->_nodes[end_idx]; b->_nodes.map(end_idx,gto); // Slam over NeverBranch _bbs.map(gto->_idx, b); C->regalloc()->set_bad(gto->_idx); b->_nodes.pop(); // Yank projections b->_nodes.pop(); // Yank projections b->_succs.map(0,succ); // Map only successor b->_num_succs = 1; // remap successor's predecessors if necessary uint j; for( j = 1; j < succ->num_preds(); j++) if( succ->pred(j)->in(0) == bp ) succ->head()->set_req(j, gto); // Kill alternate exit path Block *dead = b->_succs[1-idx]; for( j = 1; j < dead->num_preds(); j++) if( dead->pred(j)->in(0) == bp ) break; // Scan through block, yanking dead path from // all regions and phis. dead->head()->del_req(j); for( int k = 1; dead->_nodes[k]->is_Phi(); k++ ) dead->_nodes[k]->del_req(j); } //------------------------------move_to_next----------------------------------- // Helper function to move block bx to the slot following b_index. Return // true if the move is successful, otherwise false bool PhaseCFG::move_to_next(Block* bx, uint b_index) { if (bx == NULL) return false; // Return false if bx is already scheduled. uint bx_index = bx->_pre_order; if ((bx_index <= b_index) && (_blocks[bx_index] == bx)) { return false; } // Find the current index of block bx on the block list bx_index = b_index + 1; while( bx_index < _num_blocks && _blocks[bx_index] != bx ) bx_index++; assert(_blocks[bx_index] == bx, "block not found"); // If the previous block conditionally falls into bx, return false, // because moving bx will create an extra jump. for(uint k = 1; k < bx->num_preds(); k++ ) { Block* pred = _bbs[bx->pred(k)->_idx]; if (pred == _blocks[bx_index-1]) { if (pred->_num_succs != 1) { return false; } } } // Reinsert bx just past block 'b' _blocks.remove(bx_index); _blocks.insert(b_index + 1, bx); return true; } //------------------------------move_to_end------------------------------------ // Move empty and uncommon blocks to the end. void PhaseCFG::move_to_end(Block *b, uint i) { int e = b->is_Empty(); if (e != Block::not_empty) { if (e == Block::empty_with_goto) { // Remove the goto, but leave the block. b->_nodes.pop(); } // Mark this block as a connector block, which will cause it to be // ignored in certain functions such as non_connector_successor(). b->set_connector(); } // Move the empty block to the end, and don't recheck. _blocks.remove(i); _blocks.push(b); } //---------------------------set_loop_alignment-------------------------------- // Set loop alignment for every block void PhaseCFG::set_loop_alignment() { uint last = _num_blocks; assert( _blocks[0] == _broot, "" ); for (uint i = 1; i < last; i++ ) { Block *b = _blocks[i]; if (b->head()->is_Loop()) { b->set_loop_alignment(b); } } } //-----------------------------remove_empty------------------------------------ // Make empty basic blocks to be "connector" blocks, Move uncommon blocks // to the end. void PhaseCFG::remove_empty() { // Move uncommon blocks to the end uint last = _num_blocks; assert( _blocks[0] == _broot, "" ); for (uint i = 1; i < last; i++) { Block *b = _blocks[i]; if (b->is_connector()) break; // Check for NeverBranch at block end. This needs to become a GOTO to the // true target. NeverBranch are treated as a conditional branch that // always goes the same direction for most of the optimizer and are used // to give a fake exit path to infinite loops. At this late stage they // need to turn into Goto's so that when you enter the infinite loop you // indeed hang. if( b->_nodes[b->end_idx()]->Opcode() == Op_NeverBranch ) convert_NeverBranch_to_Goto(b); // Look for uncommon blocks and move to end. if (!C->do_freq_based_layout()) { if( b->is_uncommon(_bbs) ) { move_to_end(b, i); last--; // No longer check for being uncommon! if( no_flip_branch(b) ) { // Fall-thru case must follow? b = _blocks[i]; // Find the fall-thru block move_to_end(b, i); last--; } i--; // backup block counter post-increment } } } // Move empty blocks to the end last = _num_blocks; for (uint i = 1; i < last; i++) { Block *b = _blocks[i]; if (b->is_Empty() != Block::not_empty) { move_to_end(b, i); last--; i--; } } // End of for all blocks } //-----------------------------fixup_flow-------------------------------------- // Fix up the final control flow for basic blocks. void PhaseCFG::fixup_flow() { // Fixup final control flow for the blocks. Remove jump-to-next // block. If neither arm of a IF follows the conditional branch, we // have to add a second jump after the conditional. We place the // TRUE branch target in succs[0] for both GOTOs and IFs. for (uint i=0; i < _num_blocks; i++) { Block *b = _blocks[i]; b->_pre_order = i; // turn pre-order into block-index // Connector blocks need no further processing. if (b->is_connector()) { assert((i+1) == _num_blocks || _blocks[i+1]->is_connector(), "All connector blocks should sink to the end"); continue; } assert(b->is_Empty() != Block::completely_empty, "Empty blocks should be connectors"); Block *bnext = (i < _num_blocks-1) ? _blocks[i+1] : NULL; Block *bs0 = b->non_connector_successor(0); // Check for multi-way branches where I cannot negate the test to // exchange the true and false targets. if( no_flip_branch( b ) ) { // Find fall through case - if must fall into its target int branch_idx = b->_nodes.size() - b->_num_succs; for (uint j2 = 0; j2 < b->_num_succs; j2++) { const ProjNode* p = b->_nodes[branch_idx + j2]->as_Proj(); if (p->_con == 0) { // successor j2 is fall through case if (b->non_connector_successor(j2) != bnext) { // but it is not the next block => insert a goto insert_goto_at(i, j2); } // Put taken branch in slot 0 if( j2 == 0 && b->_num_succs == 2) { // Flip targets in succs map Block *tbs0 = b->_succs[0]; Block *tbs1 = b->_succs[1]; b->_succs.map( 0, tbs1 ); b->_succs.map( 1, tbs0 ); } break; } } // Remove all CatchProjs for (uint j1 = 0; j1 < b->_num_succs; j1++) b->_nodes.pop(); } else if (b->_num_succs == 1) { // Block ends in a Goto? if (bnext == bs0) { // We fall into next block; remove the Goto b->_nodes.pop(); } } else if( b->_num_succs == 2 ) { // Block ends in a If? // Get opcode of 1st projection (matches _succs[0]) // Note: Since this basic block has 2 exits, the last 2 nodes must // be projections (in any order), the 3rd last node must be // the IfNode (we have excluded other 2-way exits such as // CatchNodes already). MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach(); ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj(); ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj(); // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. assert(proj0->raw_out(0) == b->_succs[0]->head(), "Mismatch successor 0"); assert(proj1->raw_out(0) == b->_succs[1]->head(), "Mismatch successor 1"); Block *bs1 = b->non_connector_successor(1); // Check for neither successor block following the current // block ending in a conditional. If so, move one of the // successors after the current one, provided that the // successor was previously unscheduled, but moveable // (i.e., all paths to it involve a branch). if( !C->do_freq_based_layout() && bnext != bs0 && bnext != bs1 ) { // Choose the more common successor based on the probability // of the conditional branch. Block *bx = bs0; Block *by = bs1; // _prob is the probability of taking the true path. Make // p the probability of taking successor #1. float p = iff->as_MachIf()->_prob; if( proj0->Opcode() == Op_IfTrue ) { p = 1.0 - p; } // Prefer successor #1 if p > 0.5 if (p > PROB_FAIR) { bx = bs1; by = bs0; } // Attempt the more common successor first if (move_to_next(bx, i)) { bnext = bx; } else if (move_to_next(by, i)) { bnext = by; } } // Check for conditional branching the wrong way. Negate // conditional, if needed, so it falls into the following block // and branches to the not-following block. // Check for the next block being in succs[0]. We are going to branch // to succs[0], so we want the fall-thru case as the next block in // succs[1]. if (bnext == bs0) { // Fall-thru case in succs[0], so flip targets in succs map Block *tbs0 = b->_succs[0]; Block *tbs1 = b->_succs[1]; b->_succs.map( 0, tbs1 ); b->_succs.map( 1, tbs0 ); // Flip projection for each target { ProjNode *tmp = proj0; proj0 = proj1; proj1 = tmp; } } else if( bnext != bs1 ) { // Need a double-branch // The existing conditional branch need not change. // Add a unconditional branch to the false target. // Alas, it must appear in its own block and adding a // block this late in the game is complicated. Sigh. insert_goto_at(i, 1); } // Make sure we TRUE branch to the target if( proj0->Opcode() == Op_IfFalse ) { iff->as_MachIf()->negate(); } b->_nodes.pop(); // Remove IfFalse & IfTrue projections b->_nodes.pop(); } else { // Multi-exit block, e.g. a switch statement // But we don't need to do anything here } } // End of for all blocks } //------------------------------dump------------------------------------------- #ifndef PRODUCT void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const { const Node *x = end->is_block_proj(); assert( x, "not a CFG" ); // Do not visit this block again if( visited.test_set(x->_idx) ) return; // Skip through this block const Node *p = x; do { p = p->in(0); // Move control forward assert( !p->is_block_proj() || p->is_Root(), "not a CFG" ); } while( !p->is_block_start() ); // Recursively visit for( uint i=1; ireq(); i++ ) _dump_cfg(p->in(i),visited); // Dump the block _bbs[p->_idx]->dump(&_bbs); } void PhaseCFG::dump( ) const { tty->print("\n--- CFG --- %d BBs\n",_num_blocks); if( _blocks.size() ) { // Did we do basic-block layout? for( uint i=0; i<_num_blocks; i++ ) _blocks[i]->dump(&_bbs); } else { // Else do it with a DFS VectorSet visited(_bbs._arena); _dump_cfg(_root,visited); } } void PhaseCFG::dump_headers() { for( uint i = 0; i < _num_blocks; i++ ) { if( _blocks[i] == NULL ) continue; _blocks[i]->dump_head(&_bbs); } } void PhaseCFG::verify( ) const { #ifdef ASSERT // Verify sane CFG for (uint i = 0; i < _num_blocks; i++) { Block *b = _blocks[i]; uint cnt = b->_nodes.size(); uint j; for (j = 0; j < cnt; j++) { Node *n = b->_nodes[j]; assert( _bbs[n->_idx] == b, "" ); if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) { assert(j == 1 || b->_nodes[j-1]->is_Phi(), "CreateEx must be first instruction in block"); } for (uint k = 0; k < n->req(); k++) { Node *def = n->in(k); if (def && def != n) { assert(_bbs[def->_idx] || def->is_Con(), "must have block; constants for debug info ok"); // Verify that instructions in the block is in correct order. // Uses must follow their definition if they are at the same block. // Mostly done to check that MachSpillCopy nodes are placed correctly // when CreateEx node is moved in build_ifg_physical(). if (_bbs[def->_idx] == b && !(b->head()->is_Loop() && n->is_Phi()) && // See (+++) comment in reg_split.cpp !(n->jvms() != NULL && n->jvms()->is_monitor_use(k))) { bool is_loop = false; if (n->is_Phi()) { for (uint l = 1; l < def->req(); l++) { if (n == def->in(l)) { is_loop = true; break; // Some kind of loop } } } assert(is_loop || b->find_node(def) < j, "uses must follow definitions"); } } } } j = b->end_idx(); Node *bp = (Node*)b->_nodes[b->_nodes.size()-1]->is_block_proj(); assert( bp, "last instruction must be a block proj" ); assert( bp == b->_nodes[j], "wrong number of successors for this block" ); if (bp->is_Catch()) { while (b->_nodes[--j]->is_MachProj()) ; assert(b->_nodes[j]->is_MachCall(), "CatchProj must follow call"); } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) { assert(b->_num_succs == 2, "Conditional branch must have two targets"); } } #endif } #endif //============================================================================= //------------------------------UnionFind-------------------------------------- UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) { Copy::zero_to_bytes( _indices, sizeof(uint)*max ); } void UnionFind::extend( uint from_idx, uint to_idx ) { _nesting.check(); if( from_idx >= _max ) { uint size = 16; while( size <= from_idx ) size <<=1; _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size ); _max = size; } while( _cnt <= from_idx ) _indices[_cnt++] = 0; _indices[from_idx] = to_idx; } void UnionFind::reset( uint max ) { assert( max <= max_uint, "Must fit within uint" ); // Force the Union-Find mapping to be at least this large extend(max,0); // Initialize to be the ID mapping. for( uint i=0; i= _max ) return idx; uint next = lookup(idx); while( next != idx ) { // Scan chain of equivalences idx = next; // until find a fixed-point next = lookup(idx); } return next; } //------------------------------Union------------------------------------------ // union 2 sets together. void UnionFind::Union( uint idx1, uint idx2 ) { uint src = Find(idx1); uint dst = Find(idx2); assert( src, "" ); assert( dst, "" ); assert( src < _max, "oob" ); assert( dst < _max, "oob" ); assert( src < dst, "always union smaller" ); map(dst,src); } #ifndef PRODUCT void edge_dump(GrowableArray *edges) { tty->print_cr("---- Edges ----"); for (int i = 0; i < edges->length(); i++) { CFGEdge *e = edges->at(i); if (e != NULL) { edges->at(i)->dump(); } } } void trace_dump(Trace *traces[], int count) { tty->print_cr("---- Traces ----"); for (int i = 0; i < count; i++) { Trace *tr = traces[i]; if (tr != NULL) { tr->dump(); } } } void Trace::dump( ) const { tty->print_cr("Trace (freq %f)", first_block()->_freq); for (Block *b = first_block(); b != NULL; b = next(b)) { tty->print(" B%d", b->_pre_order); if (b->head()->is_Loop()) { tty->print(" (L%d)", b->compute_loop_alignment()); } if (b->has_loop_alignment()) { tty->print(" (T%d)", b->code_alignment()); } } tty->cr(); } void CFGEdge::dump( ) const { tty->print(" B%d --> B%d Freq: %f out:%3d%% in:%3d%% State: ", from()->_pre_order, to()->_pre_order, freq(), _from_pct, _to_pct); switch(state()) { case connected: tty->print("connected"); break; case open: tty->print("open"); break; case interior: tty->print("interior"); break; } if (infrequent()) { tty->print(" infrequent"); } tty->cr(); } #endif //============================================================================= //------------------------------edge_order------------------------------------- // Comparison function for edges static int edge_order(CFGEdge **e0, CFGEdge **e1) { float freq0 = (*e0)->freq(); float freq1 = (*e1)->freq(); if (freq0 != freq1) { return freq0 > freq1 ? -1 : 1; } int dist0 = (*e0)->to()->_rpo - (*e0)->from()->_rpo; int dist1 = (*e1)->to()->_rpo - (*e1)->from()->_rpo; return dist1 - dist0; } //------------------------------trace_frequency_order-------------------------- // Comparison function for edges extern "C" int trace_frequency_order(const void *p0, const void *p1) { Trace *tr0 = *(Trace **) p0; Trace *tr1 = *(Trace **) p1; Block *b0 = tr0->first_block(); Block *b1 = tr1->first_block(); // The trace of connector blocks goes at the end; // we only expect one such trace if (b0->is_connector() != b1->is_connector()) { return b1->is_connector() ? -1 : 1; } // Pull more frequently executed blocks to the beginning float freq0 = b0->_freq; float freq1 = b1->_freq; if (freq0 != freq1) { return freq0 > freq1 ? -1 : 1; } int diff = tr0->first_block()->_rpo - tr1->first_block()->_rpo; return diff; } //------------------------------find_edges------------------------------------- // Find edges of interest, i.e, those which can fall through. Presumes that // edges which don't fall through are of low frequency and can be generally // ignored. Initialize the list of traces. void PhaseBlockLayout::find_edges() { // Walk the blocks, creating edges and Traces uint i; Trace *tr = NULL; for (i = 0; i < _cfg._num_blocks; i++) { Block *b = _cfg._blocks[i]; tr = new Trace(b, next, prev); traces[tr->id()] = tr; // All connector blocks should be at the end of the list if (b->is_connector()) break; // If this block and the next one have a one-to-one successor // predecessor relationship, simply append the next block int nfallthru = b->num_fall_throughs(); while (nfallthru == 1 && b->succ_fall_through(0)) { Block *n = b->_succs[0]; // Skip over single-entry connector blocks, we don't want to // add them to the trace. while (n->is_connector() && n->num_preds() == 1) { n = n->_succs[0]; } // We see a merge point, so stop search for the next block if (n->num_preds() != 1) break; i++; assert(n = _cfg._blocks[i], "expecting next block"); tr->append(n); uf->map(n->_pre_order, tr->id()); traces[n->_pre_order] = NULL; nfallthru = b->num_fall_throughs(); b = n; } if (nfallthru > 0) { // Create a CFGEdge for each outgoing // edge that could be a fall-through. for (uint j = 0; j < b->_num_succs; j++ ) { if (b->succ_fall_through(j)) { Block *target = b->non_connector_successor(j); float freq = b->_freq * b->succ_prob(j); int from_pct = (int) ((100 * freq) / b->_freq); int to_pct = (int) ((100 * freq) / target->_freq); edges->append(new CFGEdge(b, target, freq, from_pct, to_pct)); } } } } // Group connector blocks into one trace for (i++; i < _cfg._num_blocks; i++) { Block *b = _cfg._blocks[i]; assert(b->is_connector(), "connector blocks at the end"); tr->append(b); uf->map(b->_pre_order, tr->id()); traces[b->_pre_order] = NULL; } } //------------------------------union_traces---------------------------------- // Union two traces together in uf, and null out the trace in the list void PhaseBlockLayout::union_traces(Trace* updated_trace, Trace* old_trace) { uint old_id = old_trace->id(); uint updated_id = updated_trace->id(); uint lo_id = updated_id; uint hi_id = old_id; // If from is greater than to, swap values to meet // UnionFind guarantee. if (updated_id > old_id) { lo_id = old_id; hi_id = updated_id; // Fix up the trace ids traces[lo_id] = traces[updated_id]; updated_trace->set_id(lo_id); } // Union the lower with the higher and remove the pointer // to the higher. uf->Union(lo_id, hi_id); traces[hi_id] = NULL; } //------------------------------grow_traces------------------------------------- // Append traces together via the most frequently executed edges void PhaseBlockLayout::grow_traces() { // Order the edges, and drive the growth of Traces via the most // frequently executed edges. edges->sort(edge_order); for (int i = 0; i < edges->length(); i++) { CFGEdge *e = edges->at(i); if (e->state() != CFGEdge::open) continue; Block *src_block = e->from(); Block *targ_block = e->to(); // Don't grow traces along backedges? if (!BlockLayoutRotateLoops) { if (targ_block->_rpo <= src_block->_rpo) { targ_block->set_loop_alignment(targ_block); continue; } } Trace *src_trace = trace(src_block); Trace *targ_trace = trace(targ_block); // If the edge in question can join two traces at their ends, // append one trace to the other. if (src_trace->last_block() == src_block) { if (src_trace == targ_trace) { e->set_state(CFGEdge::interior); if (targ_trace->backedge(e)) { // Reset i to catch any newly eligible edge // (Or we could remember the first "open" edge, and reset there) i = 0; } } else if (targ_trace->first_block() == targ_block) { e->set_state(CFGEdge::connected); src_trace->append(targ_trace); union_traces(src_trace, targ_trace); } } } } //------------------------------merge_traces----------------------------------- // Embed one trace into another, if the fork or join points are sufficiently // balanced. void PhaseBlockLayout::merge_traces(bool fall_thru_only) { // Walk the edge list a another time, looking at unprocessed edges. // Fold in diamonds for (int i = 0; i < edges->length(); i++) { CFGEdge *e = edges->at(i); if (e->state() != CFGEdge::open) continue; if (fall_thru_only) { if (e->infrequent()) continue; } Block *src_block = e->from(); Trace *src_trace = trace(src_block); bool src_at_tail = src_trace->last_block() == src_block; Block *targ_block = e->to(); Trace *targ_trace = trace(targ_block); bool targ_at_start = targ_trace->first_block() == targ_block; if (src_trace == targ_trace) { // This may be a loop, but we can't do much about it. e->set_state(CFGEdge::interior); continue; } if (fall_thru_only) { // If the edge links the middle of two traces, we can't do anything. // Mark the edge and continue. if (!src_at_tail & !targ_at_start) { continue; } // Don't grow traces along backedges? if (!BlockLayoutRotateLoops && (targ_block->_rpo <= src_block->_rpo)) { continue; } // If both ends of the edge are available, why didn't we handle it earlier? assert(src_at_tail ^ targ_at_start, "Should have caught this edge earlier."); if (targ_at_start) { // Insert the "targ" trace in the "src" trace if the insertion point // is a two way branch. // Better profitability check possible, but may not be worth it. // Someday, see if the this "fork" has an associated "join"; // then make a policy on merging this trace at the fork or join. // For example, other things being equal, it may be better to place this // trace at the join point if the "src" trace ends in a two-way, but // the insertion point is one-way. assert(src_block->num_fall_throughs() == 2, "unexpected diamond"); e->set_state(CFGEdge::connected); src_trace->insert_after(src_block, targ_trace); union_traces(src_trace, targ_trace); } else if (src_at_tail) { if (src_trace != trace(_cfg._broot)) { e->set_state(CFGEdge::connected); targ_trace->insert_before(targ_block, src_trace); union_traces(targ_trace, src_trace); } } } else if (e->state() == CFGEdge::open) { // Append traces, even without a fall-thru connection. // But leave root entry at the beginning of the block list. if (targ_trace != trace(_cfg._broot)) { e->set_state(CFGEdge::connected); src_trace->append(targ_trace); union_traces(src_trace, targ_trace); } } } } //----------------------------reorder_traces----------------------------------- // Order the sequence of the traces in some desirable way, and fixup the // jumps at the end of each block. void PhaseBlockLayout::reorder_traces(int count) { ResourceArea *area = Thread::current()->resource_area(); Trace ** new_traces = NEW_ARENA_ARRAY(area, Trace *, count); Block_List worklist; int new_count = 0; // Compact the traces. for (int i = 0; i < count; i++) { Trace *tr = traces[i]; if (tr != NULL) { new_traces[new_count++] = tr; } } // The entry block should be first on the new trace list. Trace *tr = trace(_cfg._broot); assert(tr == new_traces[0], "entry trace misplaced"); // Sort the new trace list by frequency qsort(new_traces + 1, new_count - 1, sizeof(new_traces[0]), trace_frequency_order); // Patch up the successor blocks _cfg._blocks.reset(); _cfg._num_blocks = 0; for (int i = 0; i < new_count; i++) { Trace *tr = new_traces[i]; if (tr != NULL) { tr->fixup_blocks(_cfg); } } } //------------------------------PhaseBlockLayout------------------------------- // Order basic blocks based on frequency PhaseBlockLayout::PhaseBlockLayout(PhaseCFG &cfg) : Phase(BlockLayout), _cfg(cfg) { ResourceMark rm; ResourceArea *area = Thread::current()->resource_area(); // List of traces int size = _cfg._num_blocks + 1; traces = NEW_ARENA_ARRAY(area, Trace *, size); memset(traces, 0, size*sizeof(Trace*)); next = NEW_ARENA_ARRAY(area, Block *, size); memset(next, 0, size*sizeof(Block *)); prev = NEW_ARENA_ARRAY(area, Block *, size); memset(prev , 0, size*sizeof(Block *)); // List of edges edges = new GrowableArray; // Mapping block index --> block_trace uf = new UnionFind(size); uf->reset(size); // Find edges and create traces. find_edges(); // Grow traces at their ends via most frequent edges. grow_traces(); // Merge one trace into another, but only at fall-through points. // This may make diamonds and other related shapes in a trace. merge_traces(true); // Run merge again, allowing two traces to be catenated, even if // one does not fall through into the other. This appends loosely // related traces to be near each other. merge_traces(false); // Re-order all the remaining traces by frequency reorder_traces(size); assert(_cfg._num_blocks >= (uint) (size - 1), "number of blocks can not shrink"); } //------------------------------backedge--------------------------------------- // Edge e completes a loop in a trace. If the target block is head of the // loop, rotate the loop block so that the loop ends in a conditional branch. bool Trace::backedge(CFGEdge *e) { bool loop_rotated = false; Block *src_block = e->from(); Block *targ_block = e->to(); assert(last_block() == src_block, "loop discovery at back branch"); if (first_block() == targ_block) { if (BlockLayoutRotateLoops && last_block()->num_fall_throughs() < 2) { // Find the last block in the trace that has a conditional // branch. Block *b; for (b = last_block(); b != NULL; b = prev(b)) { if (b->num_fall_throughs() == 2) { break; } } if (b != last_block() && b != NULL) { loop_rotated = true; // Rotate the loop by doing two-part linked-list surgery. append(first_block()); break_loop_after(b); } } // Backbranch to the top of a trace // Scroll forward through the trace from the targ_block. If we find // a loop head before another loop top, use the the loop head alignment. for (Block *b = targ_block; b != NULL; b = next(b)) { if (b->has_loop_alignment()) { break; } if (b->head()->is_Loop()) { targ_block = b; break; } } first_block()->set_loop_alignment(targ_block); } else { // Backbranch into the middle of a trace targ_block->set_loop_alignment(targ_block); } return loop_rotated; } //------------------------------fixup_blocks----------------------------------- // push blocks onto the CFG list // ensure that blocks have the correct two-way branch sense void Trace::fixup_blocks(PhaseCFG &cfg) { Block *last = last_block(); for (Block *b = first_block(); b != NULL; b = next(b)) { cfg._blocks.push(b); cfg._num_blocks++; if (!b->is_connector()) { int nfallthru = b->num_fall_throughs(); if (b != last) { if (nfallthru == 2) { // Ensure that the sense of the branch is correct Block *bnext = next(b); Block *bs0 = b->non_connector_successor(0); MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach(); ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj(); ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj(); if (bnext == bs0) { // Fall-thru case in succs[0], should be in succs[1] // Flip targets in _succs map Block *tbs0 = b->_succs[0]; Block *tbs1 = b->_succs[1]; b->_succs.map( 0, tbs1 ); b->_succs.map( 1, tbs0 ); // Flip projections to match targets b->_nodes.map(b->_nodes.size()-2, proj1); b->_nodes.map(b->_nodes.size()-1, proj0); } } } } } }