[turbofan] Implement jump threading after register allocation.

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/platform/elapsed-timer.h"
 #include "src/compiler/ast-graph-builder.h"
 #include "src/compiler/basic-block-instrumentor.h"
 #include "src/compiler/change-lowering.h"
 #include "src/compiler/code-generator.h"
 #include "src/compiler/control-reducer.h"
 #include "src/compiler/graph-replay.h"
 #include "src/compiler/graph-visualizer.h"
 #include "src/compiler/instruction.h"
 #include "src/compiler/instruction-selector.h"
 #include "src/compiler/js-context-specialization.h"
 #include "src/compiler/js-generic-lowering.h"
 #include "src/compiler/js-inlining.h"
 #include "src/compiler/js-typed-lowering.h"
+#include "src/compiler/jump-threading.h"
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/compiler/pipeline-statistics.h"
 #include "src/compiler/register-allocator.h"
 #include "src/compiler/register-allocator-verifier.h"
 #include "src/compiler/schedule.h"
 #include "src/compiler/scheduler.h"
 #include "src/compiler/select-lowering.h"
 #include "src/compiler/simplified-lowering.h"
 #include "src/compiler/simplified-operator-reducer.h"
 #include "src/compiler/typer.h"
@@ skipping 537 matching lines @@
 
 struct ResolveControlFlowPhase {
   static const char* phase_name() { return "resolve control flow"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
     data->register_allocator()->ResolveControlFlow();
   }
 };
 
 
+struct JumpThreadingPhase {
+  static const char* phase_name() { return "jump threading"; }
+
+  void Run(PipelineData* data, Zone* temp_zone) {
+    ZoneVector<BasicBlock::RpoNumber> result(temp_zone);
+    if (JumpThreading::ComputeForwarding(temp_zone, result, data->sequence())) {
+      JumpThreading::ApplyForwarding(result, data->sequence());
+    }
+  }
+};
+
+
 struct GenerateCodePhase {
   static const char* phase_name() { return "generate code"; }
 
   void Run(PipelineData* data, Zone* temp_zone, Linkage* linkage) {
     CodeGenerator generator(data->frame(), linkage, data->sequence(),
                             data->info());
     data->set_code(generator.GenerateCode());
   }
 };
 
@@ skipping 304 matching lines @@
 #endif
   // Allocate registers.
   AllocateRegisters(RegisterConfiguration::ArchDefault(), run_verifier);
   if (data->compilation_failed()) {
     info()->AbortOptimization(kNotEnoughVirtualRegistersRegalloc);
     return;
   }
 
   BeginPhaseKind("code generation");
 
-  // Generate native sequence.
+  // Optimimize jumps.
+  if (FLAG_turbo_jt) {
+    Run<JumpThreadingPhase>();
+  }
+
+  // Generate final machine code.
   Run<GenerateCodePhase>(linkage);
 
   if (profiler_data != NULL) {
 #if ENABLE_DISASSEMBLER
     std::ostringstream os;
     data->code()->Disassemble(NULL, os);
     profiler_data->SetCode(&os);
 #endif
   }
 }
@@ skipping 78 matching lines @@
 }
 
 
 void Pipeline::TearDown() {
   InstructionOperand::TearDownCaches();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8