| // Copyright 2015 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/compiler/frame-elider.h" |
| |
| #include "src/base/adapters.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| FrameElider::FrameElider(InstructionSequence* code) : code_(code) {} |
| |
| void FrameElider::Run() { |
| MarkBlocks(); |
| PropagateMarks(); |
| MarkDeConstruction(); |
| } |
| |
| |
| void FrameElider::MarkBlocks() { |
| for (InstructionBlock* block : instruction_blocks()) { |
| if (block->needs_frame()) continue; |
| for (int i = block->code_start(); i < block->code_end(); ++i) { |
| const Instruction* instr = InstructionAt(i); |
| if (instr->IsCall() || instr->IsDeoptimizeCall() || |
| instr->arch_opcode() == ArchOpcode::kArchStackPointer || |
| instr->arch_opcode() == ArchOpcode::kArchFramePointer) { |
| block->mark_needs_frame(); |
| break; |
| } |
| } |
| } |
| } |
| |
| |
| void FrameElider::PropagateMarks() { |
| while (PropagateInOrder() || PropagateReversed()) { |
| } |
| } |
| |
| |
| void FrameElider::MarkDeConstruction() { |
| for (InstructionBlock* block : instruction_blocks()) { |
| if (block->needs_frame()) { |
| // Special case: The start block needs a frame. |
| if (block->predecessors().empty()) { |
| block->mark_must_construct_frame(); |
| } |
| // Find "frame -> no frame" transitions, inserting frame |
| // deconstructions. |
| for (RpoNumber& succ : block->successors()) { |
| if (!InstructionBlockAt(succ)->needs_frame()) { |
| DCHECK_EQ(1U, block->SuccessorCount()); |
| const Instruction* last = |
| InstructionAt(block->last_instruction_index()); |
| if (last->IsThrow() || last->IsTailCall() || |
| last->IsDeoptimizeCall()) { |
| // We need to keep the frame if we exit the block through any |
| // of these. |
| continue; |
| } |
| // The only cases when we need to deconstruct are ret and jump. |
| DCHECK(last->IsRet() || last->IsJump()); |
| block->mark_must_deconstruct_frame(); |
| } |
| } |
| } else { |
| // Find "no frame -> frame" transitions, inserting frame constructions. |
| for (RpoNumber& succ : block->successors()) { |
| if (InstructionBlockAt(succ)->needs_frame()) { |
| DCHECK_NE(1U, block->SuccessorCount()); |
| InstructionBlockAt(succ)->mark_must_construct_frame(); |
| } |
| } |
| } |
| } |
| } |
| |
| |
| bool FrameElider::PropagateInOrder() { |
| bool changed = false; |
| for (InstructionBlock* block : instruction_blocks()) { |
| changed |= PropagateIntoBlock(block); |
| } |
| return changed; |
| } |
| |
| |
| bool FrameElider::PropagateReversed() { |
| bool changed = false; |
| for (InstructionBlock* block : base::Reversed(instruction_blocks())) { |
| changed |= PropagateIntoBlock(block); |
| } |
| return changed; |
| } |
| |
| |
| bool FrameElider::PropagateIntoBlock(InstructionBlock* block) { |
| // Already marked, nothing to do... |
| if (block->needs_frame()) return false; |
| |
| // Never mark the dummy end node, otherwise we might incorrectly decide to |
| // put frame deconstruction code there later, |
| if (block->successors().empty()) return false; |
| |
| // Propagate towards the end ("downwards") if there is a predecessor needing |
| // a frame, but don't "bleed" from deferred code to non-deferred code. |
| for (RpoNumber& pred : block->predecessors()) { |
| if (InstructionBlockAt(pred)->needs_frame() && |
| (!InstructionBlockAt(pred)->IsDeferred() || block->IsDeferred())) { |
| block->mark_needs_frame(); |
| return true; |
| } |
| } |
| |
| // Propagate towards start ("upwards") |
| bool need_frame_successors = false; |
| if (block->SuccessorCount() == 1) { |
| // For single successors, propagate the needs_frame information. |
| need_frame_successors = |
| InstructionBlockAt(block->successors()[0])->needs_frame(); |
| } else { |
| // For multiple successors, each successor must only have a single |
| // predecessor (because the graph is in edge-split form), so each successor |
| // can independently create/dismantle a frame if needed. Given this |
| // independent control, only propagate needs_frame if all non-deferred |
| // blocks need a frame. |
| for (RpoNumber& succ : block->successors()) { |
| InstructionBlock* successor_block = InstructionBlockAt(succ); |
| DCHECK_EQ(1, successor_block->PredecessorCount()); |
| if (!successor_block->IsDeferred()) { |
| if (successor_block->needs_frame()) { |
| need_frame_successors = true; |
| } else { |
| return false; |
| } |
| } |
| } |
| } |
| if (need_frame_successors) { |
| block->mark_needs_frame(); |
| return true; |
| } else { |
| return false; |
| } |
| } |
| |
| |
| const InstructionBlocks& FrameElider::instruction_blocks() const { |
| return code_->instruction_blocks(); |
| } |
| |
| |
| InstructionBlock* FrameElider::InstructionBlockAt(RpoNumber rpo_number) const { |
| return code_->InstructionBlockAt(rpo_number); |
| } |
| |
| |
| Instruction* FrameElider::InstructionAt(int index) const { |
| return code_->InstructionAt(index); |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |