| // Copyright 2013 the V8 project authors. All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following |
| // disclaimer in the documentation and/or other materials provided |
| // with the distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived |
| // from this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #include "hydrogen-removable-simulates.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| void HMergeRemovableSimulatesPhase::Run() { |
| ZoneList<HSimulate*> mergelist(2, zone()); |
| for (int i = 0; i < graph()->blocks()->length(); ++i) { |
| HBasicBlock* block = graph()->blocks()->at(i); |
| // Make sure the merge list is empty at the start of a block. |
| ASSERT(mergelist.is_empty()); |
| // Nasty heuristic: Never remove the first simulate in a block. This |
| // just so happens to have a beneficial effect on register allocation. |
| bool first = true; |
| for (HInstructionIterator it(block); !it.Done(); it.Advance()) { |
| HInstruction* current = it.Current(); |
| if (current->IsLeaveInlined()) { |
| // Never fold simulates from inlined environments into simulates |
| // in the outer environment. |
| // (Before each HEnterInlined, there is a non-foldable HSimulate |
| // anyway, so we get the barrier in the other direction for free.) |
| // Simply remove all accumulated simulates without merging. This |
| // is safe because simulates after instructions with side effects |
| // are never added to the merge list. |
| while (!mergelist.is_empty()) { |
| mergelist.RemoveLast()->DeleteAndReplaceWith(NULL); |
| } |
| continue; |
| } |
| if (current->IsReturn()) { |
| // Drop mergeable simulates in the list. This is safe because |
| // simulates after instructions with side effects are never added |
| // to the merge list. |
| while (!mergelist.is_empty()) { |
| mergelist.RemoveLast()->DeleteAndReplaceWith(NULL); |
| } |
| continue; |
| } |
| // Skip the non-simulates and the first simulate. |
| if (!current->IsSimulate()) continue; |
| if (first) { |
| first = false; |
| continue; |
| } |
| HSimulate* current_simulate = HSimulate::cast(current); |
| if ((current_simulate->previous()->HasObservableSideEffects() && |
| !current_simulate->next()->IsSimulate()) || |
| !current_simulate->is_candidate_for_removal()) { |
| // This simulate is not suitable for folding. |
| // Fold the ones accumulated so far. |
| current_simulate->MergeWith(&mergelist); |
| continue; |
| } else { |
| // Accumulate this simulate for folding later on. |
| mergelist.Add(current_simulate, zone()); |
| } |
| } |
| |
| if (!mergelist.is_empty()) { |
| // Merge the accumulated simulates at the end of the block. |
| HSimulate* last = mergelist.RemoveLast(); |
| last->MergeWith(&mergelist); |
| } |
| } |
| } |
| |
| } } // namespace v8::internal |