Setting up the stage for heuristics that preprocess live ranges before register allocation, and are independent of register allocation - e.g. the deferred blocks heuristic, or the split at call sites heuristic.

Added a separate flag for this, since we intend to enable it for the linear allocator as well. Currently, the option is "on" for greedy, as a point in time to enable its testing (through the greedy allocator bots).

BUG=

Review URL: https://codereview.chromium.org/1256313003

Cr-Commit-Position: refs/heads/master@{#30005}

BUILD.gn

@@ -782,6 +782,8 @@ source_set("v8_base") {
     "src/compiler/pipeline.h",
     "src/compiler/pipeline-statistics.cc",
     "src/compiler/pipeline-statistics.h",
+    "src/compiler/preprocess-live-ranges.cc",
+    "src/compiler/preprocess-live-ranges.h",
     "src/compiler/raw-machine-assembler.cc",
     "src/compiler/raw-machine-assembler.h",
     "src/compiler/register-allocator.cc",

src/compiler/pipeline.cc

@@ -42,6 +42,7 @@
 #include "src/compiler/move-optimizer.h"
 #include "src/compiler/osr.h"
 #include "src/compiler/pipeline-statistics.h"
+#include "src/compiler/preprocess-live-ranges.h"
 #include "src/compiler/register-allocator.h"
 #include "src/compiler/register-allocator-verifier.h"
 #include "src/compiler/schedule.h"
@@ -785,6 +786,17 @@ struct BuildLiveRangesPhase {
 };
 
 
+struct PreprocessLiveRangesPhase {
+  static const char* phase_name() { return "preprocess live ranges"; }
+
+  void Run(PipelineData* data, Zone* temp_zone) {
+    PreprocessLiveRanges live_range_preprocessor(
+        data->register_allocation_data(), temp_zone);
+    live_range_preprocessor.PreprocessRanges();
+  }
+};
+
+
 template <typename RegAllocator>
 struct AllocateGeneralRegistersPhase {
   static const char* phase_name() { return "allocate general registers"; }
@@ -1320,6 +1332,11 @@ void Pipeline::AllocateRegisters(const RegisterConfiguration* config,
   if (verifier != nullptr) {
     CHECK(!data->register_allocation_data()->ExistsUseWithoutDefinition());
   }
+
+  if (FLAG_turbo_preprocess_ranges) {
+    Run<PreprocessLiveRangesPhase>();
+  }
+
   if (FLAG_turbo_greedy_regalloc) {
     Run<AllocateGeneralRegistersPhase<GreedyAllocator>>();
     Run<AllocateDoubleRegistersPhase<GreedyAllocator>>();

src/compiler/preprocess-live-ranges.cc

@@ -0,0 +1,29 @@
+// 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/preprocess-live-ranges.h"
+#include "src/compiler/register-allocator.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+
+#define TRACE(...)                             \
+  do {                                         \
+    if (FLAG_trace_alloc) PrintF(__VA_ARGS__); \
+  } while (false)
+
+
+void PreprocessLiveRanges::PreprocessRanges() {
+  SplitRangesAroundDeferredBlocks();
+}
+
+
+void PreprocessLiveRanges::SplitRangesAroundDeferredBlocks() {}
+
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8

src/compiler/preprocess-live-ranges.h

@@ -0,0 +1,35 @@
+// 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.
+
+#ifndef V8_PREPROCESS_LIVE_RANGES_H_
+#define V8_PREPROCESS_LIVE_RANGES_H_
+
+#include "src/compiler/register-allocator.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+
+class PreprocessLiveRanges final {
+ public:
+  PreprocessLiveRanges(RegisterAllocationData* data, Zone* zone)
+      : data_(data), zone_(zone) {}
+  void PreprocessRanges();
+
+ private:
+  void SplitRangesAroundDeferredBlocks();
+
+  RegisterAllocationData* data() { return data_; }
+  Zone* zone() { return zone_; }
+
+  RegisterAllocationData* data_;
+  Zone* zone_;
+};
+
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+#endif  // V8_PREPROCESS_LIVE_RANGES_H_

src/flag-definitions.h

@@ -397,6 +397,9 @@ DEFINE_BOOL(omit_map_checks_for_leaf_maps, true,
 DEFINE_BOOL(turbo, false, "enable TurboFan compiler")
 DEFINE_BOOL(turbo_shipping, true, "enable TurboFan compiler on subset")
 DEFINE_BOOL(turbo_greedy_regalloc, false, "use the greedy register allocator")
+DEFINE_BOOL(turbo_preprocess_ranges, false,
+            "run pre-register allocation heuristics")
+DEFINE_IMPLICATION(turbo_greedy_regalloc, turbo_preprocess_ranges)
 DEFINE_IMPLICATION(turbo, turbo_asm_deoptimization)
 DEFINE_STRING(turbo_filter, "~~", "optimization filter for TurboFan compiler")
 DEFINE_BOOL(trace_turbo, false, "trace generated TurboFan IR")

tools/gyp/v8.gyp

@@ -575,6 +575,8 @@
         '../../src/compiler/pipeline.h',
         '../../src/compiler/pipeline-statistics.cc',
         '../../src/compiler/pipeline-statistics.h',
+        '../../src/compiler/preprocess-live-ranges.cc',
+        '../../src/compiler/preprocess-live-ranges.h',
         '../../src/compiler/raw-machine-assembler.cc',
         '../../src/compiler/raw-machine-assembler.h',
         '../../src/compiler/register-allocator.cc',