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Side by Side Diff: runtime/vm/branch_optimizer.cc

Issue 2904733003: Revert "Shuffle around deopt id allocation to give the flow graph builder a chance to record other … (Closed)
Patch Set: Created 3 years, 6 months ago
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1 // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file 1 // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
2 // for details. All rights reserved. Use of this source code is governed by a 2 // for details. All rights reserved. Use of this source code is governed by a
3 // BSD-style license that can be found in the LICENSE file. 3 // BSD-style license that can be found in the LICENSE file.
4 4
5 #include "vm/branch_optimizer.h" 5 #include "vm/branch_optimizer.h"
6 6
7 #include "vm/flow_graph.h" 7 #include "vm/flow_graph.h"
8 #include "vm/intermediate_language.h" 8 #include "vm/intermediate_language.h"
9 9
10 namespace dart { 10 namespace dart {
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58 PhiHasSingleUse(phi, left) && (block->next() == branch) && 58 PhiHasSingleUse(phi, left) && (block->next() == branch) &&
59 (block->phis()->length() == 1); 59 (block->phis()->length() == 1);
60 } 60 }
61 61
62 62
63 JoinEntryInstr* BranchSimplifier::ToJoinEntry(Zone* zone, 63 JoinEntryInstr* BranchSimplifier::ToJoinEntry(Zone* zone,
64 TargetEntryInstr* target) { 64 TargetEntryInstr* target) {
65 // Convert a target block into a join block. Branches will be duplicated 65 // Convert a target block into a join block. Branches will be duplicated
66 // so the former true and false targets become joins of the control flows 66 // so the former true and false targets become joins of the control flows
67 // from all the duplicated branches. 67 // from all the duplicated branches.
68 JoinEntryInstr* join = new (zone) JoinEntryInstr( 68 JoinEntryInstr* join =
69 target->block_id(), target->try_index(), Thread::kNoDeoptId); 69 new (zone) JoinEntryInstr(target->block_id(), target->try_index());
70 join->InheritDeoptTarget(zone, target); 70 join->InheritDeoptTarget(zone, target);
71 join->LinkTo(target->next()); 71 join->LinkTo(target->next());
72 join->set_last_instruction(target->last_instruction()); 72 join->set_last_instruction(target->last_instruction());
73 target->UnuseAllInputs(); 73 target->UnuseAllInputs();
74 return join; 74 return join;
75 } 75 }
76 76
77 77
78 BranchInstr* BranchSimplifier::CloneBranch(Zone* zone, 78 BranchInstr* BranchSimplifier::CloneBranch(Zone* zone,
79 BranchInstr* branch, 79 BranchInstr* branch,
80 Value* new_left, 80 Value* new_left,
81 Value* new_right) { 81 Value* new_right) {
82 ComparisonInstr* comparison = branch->comparison(); 82 ComparisonInstr* comparison = branch->comparison();
83 ComparisonInstr* new_comparison = 83 ComparisonInstr* new_comparison =
84 comparison->CopyWithNewOperands(new_left, new_right); 84 comparison->CopyWithNewOperands(new_left, new_right);
85 BranchInstr* new_branch = 85 BranchInstr* new_branch = new (zone) BranchInstr(new_comparison);
86 new (zone) BranchInstr(new_comparison, Thread::kNoDeoptId);
87 return new_branch; 86 return new_branch;
88 } 87 }
89 88
90 89
91 void BranchSimplifier::Simplify(FlowGraph* flow_graph) { 90 void BranchSimplifier::Simplify(FlowGraph* flow_graph) {
92 // Optimize some branches that test the value of a phi. When it is safe 91 // Optimize some branches that test the value of a phi. When it is safe
93 // to do so, push the branch to each of the predecessor blocks. This is 92 // to do so, push the branch to each of the predecessor blocks. This is
94 // an optimization when (a) it can avoid materializing a boolean object at 93 // an optimization when (a) it can avoid materializing a boolean object at
95 // the phi only to test its value, and (b) it can expose opportunities for 94 // the phi only to test its value, and (b) it can expose opportunities for
96 // constant propagation and unreachable code elimination. This 95 // constant propagation and unreachable code elimination. This
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177 old_goto->UnuseAllInputs(); 176 old_goto->UnuseAllInputs();
178 177
179 // Update the predecessor block. We may have created another 178 // Update the predecessor block. We may have created another
180 // instance of the pattern so add it to the worklist if necessary. 179 // instance of the pattern so add it to the worklist if necessary.
181 BlockEntryInstr* branch_block = new_branch->GetBlock(); 180 BlockEntryInstr* branch_block = new_branch->GetBlock();
182 branch_block->set_last_instruction(new_branch); 181 branch_block->set_last_instruction(new_branch);
183 if (branch_block->IsJoinEntry()) worklist.Add(branch_block); 182 if (branch_block->IsJoinEntry()) worklist.Add(branch_block);
184 183
185 // Connect the branch to the true and false joins, via empty target 184 // Connect the branch to the true and false joins, via empty target
186 // blocks. 185 // blocks.
187 TargetEntryInstr* true_target = 186 TargetEntryInstr* true_target = new (zone) TargetEntryInstr(
188 new (zone) TargetEntryInstr(flow_graph->max_block_id() + 1, 187 flow_graph->max_block_id() + 1, block->try_index());
189 block->try_index(), Thread::kNoDeoptId);
190 true_target->InheritDeoptTarget(zone, join_true); 188 true_target->InheritDeoptTarget(zone, join_true);
191 TargetEntryInstr* false_target = 189 TargetEntryInstr* false_target = new (zone) TargetEntryInstr(
192 new (zone) TargetEntryInstr(flow_graph->max_block_id() + 2, 190 flow_graph->max_block_id() + 2, block->try_index());
193 block->try_index(), Thread::kNoDeoptId);
194 false_target->InheritDeoptTarget(zone, join_false); 191 false_target->InheritDeoptTarget(zone, join_false);
195 flow_graph->set_max_block_id(flow_graph->max_block_id() + 2); 192 flow_graph->set_max_block_id(flow_graph->max_block_id() + 2);
196 *new_branch->true_successor_address() = true_target; 193 *new_branch->true_successor_address() = true_target;
197 *new_branch->false_successor_address() = false_target; 194 *new_branch->false_successor_address() = false_target;
198 GotoInstr* goto_true = 195 GotoInstr* goto_true = new (zone) GotoInstr(join_true);
199 new (zone) GotoInstr(join_true, Thread::kNoDeoptId);
200 goto_true->InheritDeoptTarget(zone, join_true); 196 goto_true->InheritDeoptTarget(zone, join_true);
201 true_target->LinkTo(goto_true); 197 true_target->LinkTo(goto_true);
202 true_target->set_last_instruction(goto_true); 198 true_target->set_last_instruction(goto_true);
203 GotoInstr* goto_false = 199 GotoInstr* goto_false = new (zone) GotoInstr(join_false);
204 new (zone) GotoInstr(join_false, Thread::kNoDeoptId);
205 goto_false->InheritDeoptTarget(zone, join_false); 200 goto_false->InheritDeoptTarget(zone, join_false);
206 false_target->LinkTo(goto_false); 201 false_target->LinkTo(goto_false);
207 false_target->set_last_instruction(goto_false); 202 false_target->set_last_instruction(goto_false);
208 } 203 }
209 // When all predecessors have been rewritten, the original block is 204 // When all predecessors have been rewritten, the original block is
210 // unreachable from the graph. 205 // unreachable from the graph.
211 phi->UnuseAllInputs(); 206 phi->UnuseAllInputs();
212 branch->UnuseAllInputs(); 207 branch->UnuseAllInputs();
213 block->UnuseAllInputs(); 208 block->UnuseAllInputs();
214 ASSERT(!phi->HasUses()); 209 ASSERT(!phi->HasUses());
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293 288
294 // Check if the platform supports efficient branchless IfThenElseInstr 289 // Check if the platform supports efficient branchless IfThenElseInstr
295 // for the given combination of comparison and values flowing from 290 // for the given combination of comparison and values flowing from
296 // false and true paths. 291 // false and true paths.
297 if (IfThenElseInstr::Supports(comparison, v1, v2)) { 292 if (IfThenElseInstr::Supports(comparison, v1, v2)) {
298 Value* if_true = (pred1 == branch->true_successor()) ? v1 : v2; 293 Value* if_true = (pred1 == branch->true_successor()) ? v1 : v2;
299 Value* if_false = (pred2 == branch->true_successor()) ? v1 : v2; 294 Value* if_false = (pred2 == branch->true_successor()) ? v1 : v2;
300 295
301 ComparisonInstr* new_comparison = comparison->CopyWithNewOperands( 296 ComparisonInstr* new_comparison = comparison->CopyWithNewOperands(
302 comparison->left()->Copy(zone), comparison->right()->Copy(zone)); 297 comparison->left()->Copy(zone), comparison->right()->Copy(zone));
303 IfThenElseInstr* if_then_else = new (zone) 298 IfThenElseInstr* if_then_else = new (zone) IfThenElseInstr(
304 IfThenElseInstr(new_comparison, if_true->Copy(zone), 299 new_comparison, if_true->Copy(zone), if_false->Copy(zone));
305 if_false->Copy(zone), Thread::kNoDeoptId);
306 flow_graph->InsertBefore(branch, if_then_else, NULL, 300 flow_graph->InsertBefore(branch, if_then_else, NULL,
307 FlowGraph::kValue); 301 FlowGraph::kValue);
308 302
309 phi->ReplaceUsesWith(if_then_else); 303 phi->ReplaceUsesWith(if_then_else);
310 304
311 // Connect IfThenElseInstr to the first instruction in the merge block 305 // Connect IfThenElseInstr to the first instruction in the merge block
312 // effectively eliminating diamond control flow. 306 // effectively eliminating diamond control flow.
313 // Current block as well as pred1 and pred2 blocks are no longer in 307 // Current block as well as pred1 and pred2 blocks are no longer in
314 // the graph at this point. 308 // the graph at this point.
315 if_then_else->LinkTo(join->next()); 309 if_then_else->LinkTo(join->next());
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341 if (changed) { 335 if (changed) {
342 // We may have changed the block order and the dominator tree. 336 // We may have changed the block order and the dominator tree.
343 flow_graph->DiscoverBlocks(); 337 flow_graph->DiscoverBlocks();
344 GrowableArray<BitVector*> dominance_frontier; 338 GrowableArray<BitVector*> dominance_frontier;
345 flow_graph->ComputeDominators(&dominance_frontier); 339 flow_graph->ComputeDominators(&dominance_frontier);
346 } 340 }
347 } 341 }
348 342
349 343
350 } // namespace dart 344 } // namespace dart
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