diff -r 000000000000 -r f90c822e73f8 src/share/vm/opto/block.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/opto/block.cpp Wed Apr 27 01:25:04 2016 +0800 @@ -0,0 +1,1769 @@ +/* + * Copyright (c) 1997, 2014, 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" + +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 = number_of_nodes(); + for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) { + uint inst_size = get_node(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 < number_of_nodes(); i++ ) { + if( get_node(i) == n ) + return i; + } + ShouldNotReachHere(); + return 0; +} + +// Find and remove n from block list +void Block::find_remove( const Node *n ) { + remove_node(find_node(n)); +} + +bool Block::contains(const Node *n) const { + return _nodes.contains(n); +} + +// 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 = number_of_nodes() - 1; + + // Check for ending goto + if ((end_idx > 0) && (get_node(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) && !get_node(end_idx)->is_Mach()) { + end_idx--; + } + + // No room for any interesting instructions? + if (end_idx == 0) { + return success_result; + } + + return not_empty; +} + +// 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; +} + +// True if block is low enough frequency or guarded by a test which +// mostly does not go here. +bool PhaseCFG::is_uncommon(const Block* block) { + // Initial blocks must never be moved, so are never uncommon. + if (block->head()->is_Root() || block->head()->is_Start()) return false; + + // Check for way-low freq + if(block->_freq < BLOCK_FREQUENCY(0.00001f) ) return true; + + // Look for code shape indicating uncommon_trap or slow path + if (block->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< block->num_preds(); i++ ) { + Block* guard = get_block_for_node(block->pred(i)); + // 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(block->_freq < guard->_freq * guard_factor ) { + uncommon_for_freq_preds++; + } + } + } + if( block->num_preds() > 1 && + // The block is uncommon if all preds are uncommon or + (uncommon_preds == (block->num_preds()-1) || + // it is uncommon for all frequent preds. + uncommon_for_freq_preds == freq_preds) ) { + return true; + } + return false; +} + +#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 PhaseCFG* cfg, Block* orig, outputStream* st) const { + if (is_connector()) { + for (uint i=1; iget_block_for_node(pred(i)); + p->dump_pred(cfg, orig, st); + } + } else { + dump_bidx(orig, st); + st->print(" "); + } +} + +void Block::dump_head(const PhaseCFG* cfg, 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; iget_block_for_node(s); + p->dump_pred(cfg, 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 ((cfg != NULL) && bh->is_Loop() && !head()->is_Root()) { + LoopNode *loop = bh->as_Loop(); + const Block *bx = cfg->get_block_for_node(loop->in(LoopNode::LoopBackControl)); + while (bx->is_connector()) { + bx = cfg->get_block_for_node(bx->pred(1)); + } + 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->cr(); +} + +void Block::dump() const { + dump(NULL); +} + +void Block::dump(const PhaseCFG* cfg) const { + dump_head(cfg); + for (uint i=0; i< number_of_nodes(); i++) { + get_node(i)->dump(); + } + tty->print("\n"); +} +#endif + +PhaseCFG::PhaseCFG(Arena* arena, RootNode* root, Matcher& matcher) +: Phase(CFG) +, _block_arena(arena) +, _root(root) +, _matcher(matcher) +, _node_to_block_mapping(arena) +, _node_latency(NULL) +#ifndef PRODUCT +, _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining")) +#endif +#ifdef ASSERT +, _raw_oops(arena) +#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 = matcher.match_tree(x); + assert(_goto != NULL, ""); + _goto->set_req(0,_goto); + + // Build the CFG in Reverse Post Order + _number_of_blocks = build_cfg(); + _root_block = get_block_for_node(_root); +} + +// 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 (_block_arena) Block(_block_arena, p); + map_node_to_block(p, bb); + map_node_to_block(x, bb); + if( x != p ) { // Only for root is x == p + bb->push_node((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 = get_block_for_node(x); + // Insert into nodes array, if not already there + if (!has_block(proj)) { + assert( x != proj, "" ); + // Map basic block of projection + map_node_to_block(proj, pb); + pb->push_node(proj); + } + // Insert self as a child of my predecessor block + pb->_succs.map(pb->_num_succs++, get_block_for_node(np)); + assert( pb->get_node(pb->number_of_nodes() - 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; +} + +// 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 < number_of_blocks(), "illegal block number"); + Block* in = get_block(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->get_node(in->number_of_nodes() - 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 (_block_arena) Block(_block_arena, region); + map_node_to_block(region, 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->push_node(gto); + map_node_to_block(gto, 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 + add_block_at(block_no + 1, block); +} + +// 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->number_of_nodes() - b->_num_succs-1; + if (branch_idx < 1) { + return false; + } + Node *branch = b->get_node(branch_idx); + if (branch->is_Catch()) { + return true; + } + if (branch->is_Mach()) { + if (branch->is_MachNullCheck()) { + return true; + } + int iop = branch->as_Mach()->ideal_Opcode(); + if (iop == Op_FastLock || iop == Op_FastUnlock) { + return true; + } + // Don't flip if branch has an implicit check. + if (branch->as_Mach()->is_TrapBasedCheckNode()) { + return true; + } + } + return false; +} + +// 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->get_node(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->get_node(end_idx); + b->map_node(gto, end_idx); // Slam over NeverBranch + map_node_to_block(gto, b); + C->regalloc()->set_bad(gto->_idx); + b->pop_node(); // Yank projections + b->pop_node(); // 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->get_node(k)->is_Phi(); k++ ) + dead->get_node(k)->del_req(j); +} + +// 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) && (get_block(bx_index) == bx)) { + return false; + } + + // Find the current index of block bx on the block list + bx_index = b_index + 1; + while (bx_index < number_of_blocks() && get_block(bx_index) != bx) { + bx_index++; + } + assert(get_block(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 = get_block_for_node(bx->pred(k)); + if (pred == get_block(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 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->pop_node(); + } + // 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 for every block +void PhaseCFG::set_loop_alignment() { + uint last = number_of_blocks(); + assert(get_block(0) == get_root_block(), ""); + + for (uint i = 1; i < last; i++) { + Block* block = get_block(i); + if (block->head()->is_Loop()) { + block->set_loop_alignment(block); + } + } +} + +// Make empty basic blocks to be "connector" blocks, Move uncommon blocks +// to the end. +void PhaseCFG::remove_empty_blocks() { + // Move uncommon blocks to the end + uint last = number_of_blocks(); + assert(get_block(0) == get_root_block(), ""); + + for (uint i = 1; i < last; i++) { + Block* block = get_block(i); + if (block->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 (block->get_node(block->end_idx())->Opcode() == Op_NeverBranch) { + convert_NeverBranch_to_Goto(block); + } + + // Look for uncommon blocks and move to end. + if (!C->do_freq_based_layout()) { + if (is_uncommon(block)) { + move_to_end(block, i); + last--; // No longer check for being uncommon! + if (no_flip_branch(block)) { // Fall-thru case must follow? + // Find the fall-thru block + block = get_block(i); + move_to_end(block, i); + last--; + } + // backup block counter post-increment + i--; + } + } + } + + // Move empty blocks to the end + last = number_of_blocks(); + for (uint i = 1; i < last; i++) { + Block* block = get_block(i); + if (block->is_Empty() != Block::not_empty) { + move_to_end(block, i); + last--; + i--; + } + } // End of for all blocks +} + +Block *PhaseCFG::fixup_trap_based_check(Node *branch, Block *block, int block_pos, Block *bnext) { + // Trap based checks must fall through to the successor with + // PROB_ALWAYS. + // They should be an If with 2 successors. + assert(branch->is_MachIf(), "must be If"); + assert(block->_num_succs == 2, "must have 2 successors"); + + // Get the If node and the projection for the first successor. + MachIfNode *iff = block->get_node(block->number_of_nodes()-3)->as_MachIf(); + ProjNode *proj0 = block->get_node(block->number_of_nodes()-2)->as_Proj(); + ProjNode *proj1 = block->get_node(block->number_of_nodes()-1)->as_Proj(); + ProjNode *projt = (proj0->Opcode() == Op_IfTrue) ? proj0 : proj1; + ProjNode *projf = (proj0->Opcode() == Op_IfFalse) ? proj0 : proj1; + + // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. + assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0"); + assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1"); + + ProjNode *proj_always; + ProjNode *proj_never; + // We must negate the branch if the implicit check doesn't follow + // the branch's TRUE path. Then, the new TRUE branch target will + // be the old FALSE branch target. + if (iff->_prob <= 2*PROB_NEVER) { // There are small rounding errors. + proj_never = projt; + proj_always = projf; + } else { + // We must negate the branch if the trap doesn't follow the + // branch's TRUE path. Then, the new TRUE branch target will + // be the old FALSE branch target. + proj_never = projf; + proj_always = projt; + iff->negate(); + } + assert(iff->_prob <= 2*PROB_NEVER, "Trap based checks are expected to trap never!"); + // Map the successors properly + block->_succs.map(0, get_block_for_node(proj_never ->raw_out(0))); // The target of the trap. + block->_succs.map(1, get_block_for_node(proj_always->raw_out(0))); // The fall through target. + + if (block->get_node(block->number_of_nodes() - block->_num_succs + 1) != proj_always) { + block->map_node(proj_never, block->number_of_nodes() - block->_num_succs + 0); + block->map_node(proj_always, block->number_of_nodes() - block->_num_succs + 1); + } + + // Place the fall through block after this block. + Block *bs1 = block->non_connector_successor(1); + if (bs1 != bnext && move_to_next(bs1, block_pos)) { + bnext = bs1; + } + // If the fall through block still is not the next block, insert a goto. + if (bs1 != bnext) { + insert_goto_at(block_pos, 1); + } + return bnext; +} + +// 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 an 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 < number_of_blocks(); i++) { + Block* block = get_block(i); + block->_pre_order = i; // turn pre-order into block-index + + // Connector blocks need no further processing. + if (block->is_connector()) { + assert((i+1) == number_of_blocks() || get_block(i + 1)->is_connector(), "All connector blocks should sink to the end"); + continue; + } + assert(block->is_Empty() != Block::completely_empty, "Empty blocks should be connectors"); + + Block* bnext = (i < number_of_blocks() - 1) ? get_block(i + 1) : NULL; + Block* bs0 = block->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(block)) { + // Find fall through case - if must fall into its target. + // Get the index of the branch's first successor. + int branch_idx = block->number_of_nodes() - block->_num_succs; + + // The branch is 1 before the branch's first successor. + Node *branch = block->get_node(branch_idx-1); + + // Handle no-flip branches which have implicit checks and which require + // special block ordering and individual semantics of the 'fall through + // case'. + if ((TrapBasedNullChecks || TrapBasedRangeChecks) && + branch->is_Mach() && branch->as_Mach()->is_TrapBasedCheckNode()) { + bnext = fixup_trap_based_check(branch, block, i, bnext); + } else { + // Else, default handling for no-flip branches + for (uint j2 = 0; j2 < block->_num_succs; j2++) { + const ProjNode* p = block->get_node(branch_idx + j2)->as_Proj(); + if (p->_con == 0) { + // successor j2 is fall through case + if (block->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 && block->_num_succs == 2) { + // Flip targets in succs map + Block *tbs0 = block->_succs[0]; + Block *tbs1 = block->_succs[1]; + block->_succs.map(0, tbs1); + block->_succs.map(1, tbs0); + } + break; + } + } + } + + // Remove all CatchProjs + for (uint j = 0; j < block->_num_succs; j++) { + block->pop_node(); + } + + } else if (block->_num_succs == 1) { + // Block ends in a Goto? + if (bnext == bs0) { + // We fall into next block; remove the Goto + block->pop_node(); + } + + } else if(block->_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 = block->get_node(block->number_of_nodes() - 3)->as_Mach(); + ProjNode* proj0 = block->get_node(block->number_of_nodes() - 2)->as_Proj(); + ProjNode* proj1 = block->get_node(block->number_of_nodes() - 1)->as_Proj(); + + // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1]. + assert(proj0->raw_out(0) == block->_succs[0]->head(), "Mismatch successor 0"); + assert(proj1->raw_out(0) == block->_succs[1]->head(), "Mismatch successor 1"); + + Block* bs1 = block->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 = block->_succs[0]; + Block* tbs1 = block->_succs[1]; + block->_succs.map(0, tbs1); + block->_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(); + } + + block->pop_node(); // Remove IfFalse & IfTrue projections + block->pop_node(); + + } else { + // Multi-exit block, e.g. a switch statement + // But we don't need to do anything here + } + } // End of for all blocks +} + + +// postalloc_expand: Expand nodes after register allocation. +// +// postalloc_expand has to be called after register allocation, just +// before output (i.e. scheduling). It only gets called if +// Matcher::require_postalloc_expand is true. +// +// Background: +// +// Nodes that are expandend (one compound node requiring several +// assembler instructions to be implemented split into two or more +// non-compound nodes) after register allocation are not as nice as +// the ones expanded before register allocation - they don't +// participate in optimizations as global code motion. But after +// register allocation we can expand nodes that use registers which +// are not spillable or registers that are not allocated, because the +// old compound node is simply replaced (in its location in the basic +// block) by a new subgraph which does not contain compound nodes any +// more. The scheduler called during output can later on process these +// non-compound nodes. +// +// Implementation: +// +// Nodes requiring postalloc expand are specified in the ad file by using +// a postalloc_expand statement instead of ins_encode. A postalloc_expand +// contains a single call to an encoding, as does an ins_encode +// statement. Instead of an emit() function a postalloc_expand() function +// is generated that doesn't emit assembler but creates a new +// subgraph. The code below calls this postalloc_expand function for each +// node with the appropriate attribute. This function returns the new +// nodes generated in an array passed in the call. The old node, +// potential MachTemps before and potential Projs after it then get +// disconnected and replaced by the new nodes. The instruction +// generating the result has to be the last one in the array. In +// general it is assumed that Projs after the node expanded are +// kills. These kills are not required any more after expanding as +// there are now explicitly visible def-use chains and the Projs are +// removed. This does not hold for calls: They do not only have +// kill-Projs but also Projs defining values. Therefore Projs after +// the node expanded are removed for all but for calls. If a node is +// to be reused, it must be added to the nodes list returned, and it +// will be added again. +// +// Implementing the postalloc_expand function for a node in an enc_class +// is rather tedious. It requires knowledge about many node details, as +// the nodes and the subgraph must be hand crafted. To simplify this, +// adlc generates some utility variables into the postalloc_expand function, +// e.g., holding the operands as specified by the postalloc_expand encoding +// specification, e.g.: +// * unsigned idx_ holding the index of the node in the ins +// * Node *n_ holding the node loaded from the ins +// * MachOpnd *op_ holding the corresponding operand +// +// The ordering of operands can not be determined by looking at a +// rule. Especially if a match rule matches several different trees, +// several nodes are generated from one instruct specification with +// different operand orderings. In this case the adlc generated +// variables are the only way to access the ins and operands +// deterministically. +// +// If assigning a register to a node that contains an oop, don't +// forget to call ra_->set_oop() for the node. +void PhaseCFG::postalloc_expand(PhaseRegAlloc* _ra) { + GrowableArray new_nodes(32); // Array with new nodes filled by postalloc_expand function of node. + GrowableArray remove(32); + GrowableArray succs(32); + unsigned int max_idx = C->unique(); // Remember to distinguish new from old nodes. + DEBUG_ONLY(bool foundNode = false); + + // for all blocks + for (uint i = 0; i < number_of_blocks(); i++) { + Block *b = _blocks[i]; + // For all instructions in the current block. + for (uint j = 0; j < b->number_of_nodes(); j++) { + Node *n = b->get_node(j); + if (n->is_Mach() && n->as_Mach()->requires_postalloc_expand()) { +#ifdef ASSERT + if (TracePostallocExpand) { + if (!foundNode) { + foundNode = true; + tty->print("POSTALLOC EXPANDING %d %s\n", C->compile_id(), + C->method() ? C->method()->name()->as_utf8() : C->stub_name()); + } + tty->print(" postalloc expanding "); n->dump(); + if (Verbose) { + tty->print(" with ins:\n"); + for (uint k = 0; k < n->len(); ++k) { + if (n->in(k)) { tty->print(" "); n->in(k)->dump(); } + } + } + } +#endif + new_nodes.clear(); + // Collect nodes that have to be removed from the block later on. + uint req = n->req(); + remove.clear(); + for (uint k = 0; k < req; ++k) { + if (n->in(k) && n->in(k)->is_MachTemp()) { + remove.push(n->in(k)); // MachTemps which are inputs to the old node have to be removed. + n->in(k)->del_req(0); + j--; + } + } + + // Check whether we can allocate enough nodes. We set a fix limit for + // the size of postalloc expands with this. + uint unique_limit = C->unique() + 40; + if (unique_limit >= _ra->node_regs_max_index()) { + Compile::current()->record_failure("out of nodes in postalloc expand"); + return; + } + + // Emit (i.e. generate new nodes). + n->as_Mach()->postalloc_expand(&new_nodes, _ra); + + assert(C->unique() < unique_limit, "You allocated too many nodes in your postalloc expand."); + + // Disconnect the inputs of the old node. + // + // We reuse MachSpillCopy nodes. If we need to expand them, there + // are many, so reusing pays off. If reused, the node already + // has the new ins. n must be the last node on new_nodes list. + if (!n->is_MachSpillCopy()) { + for (int k = req - 1; k >= 0; --k) { + n->del_req(k); + } + } + +#ifdef ASSERT + // Check that all nodes have proper operands. + for (int k = 0; k < new_nodes.length(); ++k) { + if (new_nodes.at(k)->_idx < max_idx || !new_nodes.at(k)->is_Mach()) continue; // old node, Proj ... + MachNode *m = new_nodes.at(k)->as_Mach(); + for (unsigned int l = 0; l < m->num_opnds(); ++l) { + if (MachOper::notAnOper(m->_opnds[l])) { + outputStream *os = tty; + os->print("Node %s ", m->Name()); + os->print("has invalid opnd %d: %p\n", l, m->_opnds[l]); + assert(0, "Invalid operands, see inline trace in hs_err_pid file."); + } + } + } +#endif + + // Collect succs of old node in remove (for projections) and in succs (for + // all other nodes) do _not_ collect projections in remove (but in succs) + // in case the node is a call. We need the projections for calls as they are + // associated with registes (i.e. they are defs). + succs.clear(); + for (DUIterator k = n->outs(); n->has_out(k); k++) { + if (n->out(k)->is_Proj() && !n->is_MachCall() && !n->is_MachBranch()) { + remove.push(n->out(k)); + } else { + succs.push(n->out(k)); + } + } + // Replace old node n as input of its succs by last of the new nodes. + for (int k = 0; k < succs.length(); ++k) { + Node *succ = succs.at(k); + for (uint l = 0; l < succ->req(); ++l) { + if (succ->in(l) == n) { + succ->set_req(l, new_nodes.at(new_nodes.length() - 1)); + } + } + for (uint l = succ->req(); l < succ->len(); ++l) { + if (succ->in(l) == n) { + succ->set_prec(l, new_nodes.at(new_nodes.length() - 1)); + } + } + } + + // Index of old node in block. + uint index = b->find_node(n); + // Insert new nodes into block and map them in nodes->blocks array + // and remember last node in n2. + Node *n2 = NULL; + for (int k = 0; k < new_nodes.length(); ++k) { + n2 = new_nodes.at(k); + b->insert_node(n2, ++index); + map_node_to_block(n2, b); + } + + // Add old node n to remove and remove them all from block. + remove.push(n); + j--; +#ifdef ASSERT + if (TracePostallocExpand && Verbose) { + tty->print(" removing:\n"); + for (int k = 0; k < remove.length(); ++k) { + tty->print(" "); remove.at(k)->dump(); + } + tty->print(" inserting:\n"); + for (int k = 0; k < new_nodes.length(); ++k) { + tty->print(" "); new_nodes.at(k)->dump(); + } + } +#endif + for (int k = 0; k < remove.length(); ++k) { + if (b->contains(remove.at(k))) { + b->find_remove(remove.at(k)); + } else { + assert(remove.at(k)->is_Proj() && (remove.at(k)->in(0)->is_MachBranch()), ""); + } + } + // If anything has been inserted (n2 != NULL), continue after last node inserted. + // This does not always work. Some postalloc expands don't insert any nodes, if they + // do optimizations (e.g., max(x,x)). In this case we decrement j accordingly. + j = n2 ? b->find_node(n2) : j; + } + } + } + +#ifdef ASSERT + if (foundNode) { + tty->print("FINISHED %d %s\n", C->compile_id(), + C->method() ? C->method()->name()->as_utf8() : C->stub_name()); + tty->flush(); + } +#endif +} + + +//------------------------------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; i < p->req(); i++) { + _dump_cfg(p->in(i), visited); + } + + // Dump the block + get_block_for_node(p)->dump(this); +} + +void PhaseCFG::dump( ) const { + tty->print("\n--- CFG --- %d BBs\n", number_of_blocks()); + if (_blocks.size()) { // Did we do basic-block layout? + for (uint i = 0; i < number_of_blocks(); i++) { + const Block* block = get_block(i); + block->dump(this); + } + } else { // Else do it with a DFS + VectorSet visited(_block_arena); + _dump_cfg(_root,visited); + } +} + +void PhaseCFG::dump_headers() { + for (uint i = 0; i < number_of_blocks(); i++) { + Block* block = get_block(i); + if (block != NULL) { + block->dump_head(this); + } + } +} + +void PhaseCFG::verify() const { +#ifdef ASSERT + // Verify sane CFG + for (uint i = 0; i < number_of_blocks(); i++) { + Block* block = get_block(i); + uint cnt = block->number_of_nodes(); + uint j; + for (j = 0; j < cnt; j++) { + Node *n = block->get_node(j); + assert(get_block_for_node(n) == block, ""); + if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) { + assert(j == 1 || block->get_node(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(get_block_for_node(def) || 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 (get_block_for_node(def) == block && !(block->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 || block->find_node(def) < j, "uses must follow definitions"); + } + } + } + } + + j = block->end_idx(); + Node* bp = (Node*)block->get_node(block->number_of_nodes() - 1)->is_block_proj(); + assert(bp, "last instruction must be a block proj"); + assert(bp == block->get_node(j), "wrong number of successors for this block"); + if (bp->is_Catch()) { + while (block->get_node(--j)->is_MachProj()) { + ; + } + assert(block->get_node(j)->is_MachCall(), "CatchProj must follow call"); + } else if (bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If) { + assert(block->_num_succs == 2, "Conditional branch must have two targets"); + } + } +#endif +} +#endif + +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 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 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 + +// 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; +} + +// 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 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.number_of_blocks(); i++) { + Block* b = _cfg.get_block(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.get_block(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.number_of_blocks(); i++) { + Block *b = _cfg.get_block(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 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; +} + +// 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); + } + } + } +} + +// 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.get_root_block())) { + 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.get_root_block())) { + e->set_state(CFGEdge::connected); + src_trace->append(targ_trace); + union_traces(src_trace, targ_trace); + } + } + } +} + +// 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.get_root_block()); + 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.clear_blocks(); + for (int i = 0; i < new_count; i++) { + Trace *tr = new_traces[i]; + if (tr != NULL) { + tr->fixup_blocks(_cfg); + } + } +} + +// 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.number_of_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.number_of_blocks() >= (uint) (size - 1), "number of blocks can not shrink"); +} + + +// 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; +} + +// 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.add_block(b); + 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->get_node(b->number_of_nodes() - 3)->as_Mach(); + ProjNode *proj0 = b->get_node(b->number_of_nodes() - 2)->as_Proj(); + ProjNode *proj1 = b->get_node(b->number_of_nodes() - 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->map_node(proj1, b->number_of_nodes() - 2); + b->map_node(proj0, b->number_of_nodes() - 1); + } + } + } + } + } +}