[turbofan] Jump threading awareness of frame elision.

src/compiler/pipeline.cc

 // Copyright 2014 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/pipeline.h"
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
 
 #include "src/base/adapters.h"
@@ skipping 964 matching lines @@
 
   void Run(PipelineData* data, Zone* temp_zone) {
     FrameElider(data->sequence()).Run();
   }
 };
 
 
 struct JumpThreadingPhase {
   static const char* phase_name() { return "jump threading"; }
 
-  void Run(PipelineData* data, Zone* temp_zone) {
+  void Run(PipelineData* data, Zone* temp_zone, bool frame_at_start) {
     ZoneVector<RpoNumber> result(temp_zone);
-    if (JumpThreading::ComputeForwarding(temp_zone, result, data->sequence())) {
+    if (JumpThreading::ComputeForwarding(temp_zone, result, data->sequence(),
+                                         frame_at_start)) {
       JumpThreading::ApplyForwarding(result, data->sequence());
     }
   }
 };
 
 
 struct GenerateCodePhase {
   static const char* phase_name() { return "generate code"; }
 
   void Run(PipelineData* data, Zone* temp_zone, Linkage* linkage) {
@@ skipping 329 matching lines @@
   // Allocate registers.
   AllocateRegisters(
       RegisterConfiguration::ArchDefault(RegisterConfiguration::TURBOFAN),
       call_descriptor, run_verifier);
   if (data->compilation_failed()) {
     info()->AbortOptimization(kNotEnoughVirtualRegistersRegalloc);
     return Handle<Code>();
   }
 
   BeginPhaseKind("code generation");
-
+  // TODO(mtrofin): move this off to the register allocator.

[Jarin, 2016/01/28 05:26:58]

Yes, please do.

+  bool generate_frame_at_start =
+      !FLAG_turbo_frame_elision || !data_->info()->IsStub() ||
+      !data_->frame()->needs_frame() ||
+      data_->sequence()->instruction_blocks().front()->needs_frame() ||
+      linkage.GetIncomingDescriptor()->CalleeSavedFPRegisters() != 0 ||
+      linkage.GetIncomingDescriptor()->CalleeSavedRegisters() != 0;
   // Optimimize jumps.
   if (FLAG_turbo_jt) {
-    Run<JumpThreadingPhase>();
+    Run<JumpThreadingPhase>(generate_frame_at_start);
   }
 
   // Generate final machine code.
   Run<GenerateCodePhase>(&linkage);
 
   Handle<Code> code = data->code();
   if (profiler_data != nullptr) {
 #if ENABLE_DISASSEMBLER
     std::ostringstream os;
     code->Disassemble(nullptr, os);
@@ skipping 122 matching lines @@
     tcf << AsC1VRegisterAllocationData("CodeGen",
                                        data->register_allocation_data());
   }
 
   data->DeleteRegisterAllocationZone();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8