[turbofan] Frame elision for code stubs

src/compiler/frame-elider.cc

 // 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/base/adapters.h"
 #include "src/compiler/frame-elider.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) {
-      if (InstructionAt(i)->IsCall() ||
-          InstructionAt(i)->opcode() == ArchOpcode::kArchDeoptimize) {
+      const Instruction* instr = InstructionAt(i);
+      if (instr->IsCall() || instr->IsDeoptimizeCall() ||
+          instr->arch_opcode() == ArchOpcode::kArchStackPointer) {
         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();
         }
@@ skipping 59 matching lines @@
 }
 
 
 Instruction* FrameElider::InstructionAt(int index) const {
   return code_->InstructionAt(index);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8