[turbofan] Frame elision for code stubs

src/compiler/frame-elider.cc

Index: src/compiler/frame-elider.cc
diff --git a/src/compiler/frame-elider.cc b/src/compiler/frame-elider.cc
index 172a724dd8a744dce535f47f96ec9f1342d3d4d1..8b9d20bcb4e88c892f63c3269b106d698797c2f0 100644
--- a/src/compiler/frame-elider.cc
+++ b/src/compiler/frame-elider.cc
@@ -2,8 +2,9 @@
 // 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"
+#include "src/base/adapters.h"
+#include "src/compiler/linkage.h"
 
 namespace v8 {
 namespace internal {
@@ -11,19 +12,23 @@ namespace compiler {
 
 FrameElider::FrameElider(InstructionSequence* code) : code_(code) {}
 
-void FrameElider::Run() {
+void FrameElider::Run(const CallDescriptor* descriptor) {
   MarkBlocks();
   PropagateMarks();
   MarkDeConstruction();
 }
 
+bool IsDeoptimize(const Instruction* instr) {
+  return instr->arch_opcode() == ArchOpcode::kArchDeoptimize ||
+         FlagsModeField::decode(instr->opcode()) == kFlags_deoptimize;
+}
 
 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) {
+      if (InstructionAt(i)->IsCall() || IsDeoptimize(InstructionAt(i)) ||
+          InstructionAt(i)->arch_opcode() == ArchOpcode::kArchStackPointer) {
         block->mark_needs_frame();
         break;
       }
@@ -33,7 +38,7 @@ void FrameElider::MarkBlocks() {
 
 
 void FrameElider::PropagateMarks() {
-  while (PropagateInOrder() && PropagateReversed()) {
+  while (PropagateInOrder() || PropagateReversed()) {
   }
 }
 
@@ -47,10 +52,37 @@ void FrameElider::MarkDeConstruction() {
       }
       // Find "frame -> no frame" transitions, inserting frame
       // deconstructions.
+      // TODO(mtrofin): we currently have to deal with deferred blocks
+      // that branch to deferred on non-deferred blocks, and when
+      // the deferred path continues to need a frame, while the non-deferred
+      // one doesn't. To avoid penalizing the non-deferred path with the cost of
+      // deconstruction, we deconstruct and reconstruct on the deferred path.
+      // This is a bit hacky and inefficient (code size). Alternatively, we
+      // should insert a deferred block on the edge between the deferred block
+      // and the non-deferred one, so we may insert there the deconstruction.
+      bool makes_switch = false;
       for (RpoNumber& succ : block->successors()) {
         if (!InstructionBlockAt(succ)->needs_frame()) {
-          DCHECK_EQ(1U, block->SuccessorCount());
-          block->mark_must_deconstruct_frame();
+          makes_switch = true;
+          break;
+        }
+      }
+      if (!makes_switch) continue;
+
+      ArchOpcode last_opcode =
+          code_->InstructionAt(block->last_instruction_index())->arch_opcode();
+      if (last_opcode == kArchThrowTerminator ||
+          IsDeoptimize(code_->InstructionAt(block->last_instruction_index()))) {
+        continue;
+      }
+      block->mark_must_deconstruct_frame();
+      if (block->SuccessorCount() > 1) {
+        for (RpoNumber& succ : block->successors()) {
+          InstructionBlock* succ_block = InstructionBlockAt(succ);
+          if (succ_block->needs_frame() && succ_block->IsDeferred()) {
+            succ_block->mark_must_construct_frame();
+          }
+          DCHECK_IMPLIES(!succ_block->IsDeferred(), !succ_block->needs_frame());
         }
       }
     } else {