Add flag --trace-phase to selectively produce IR trace output.

src/x64/lithium-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 364 matching lines @@
   int index = GetNextSpillIndex(is_double);
   if (is_double) {
     return LDoubleStackSlot::Create(index);
   } else {
     return LStackSlot::Create(index);
   }
 }
 
 
 void LChunk::MarkEmptyBlocks() {
-  HPhase phase("Mark empty blocks", this);
+  HPhase phase("L Mark empty blocks", this);
   for (int i = 0; i < graph()->blocks()->length(); ++i) {
     HBasicBlock* block = graph()->blocks()->at(i);
     int first = block->first_instruction_index();
     int last = block->last_instruction_index();
     LInstruction* first_instr = instructions()->at(first);
     LInstruction* last_instr = instructions()->at(last);
 
     LLabel* label = LLabel::cast(first_instr);
     if (last_instr->IsGoto()) {
       LGoto* goto_instr = LGoto::cast(last_instr);
@@ skipping 142 matching lines @@
 
 Representation LChunk::LookupLiteralRepresentation(
     LConstantOperand* operand) const {
   return graph_->LookupValue(operand->index())->representation();
 }
 
 
 LChunk* LChunkBuilder::Build() {
   ASSERT(is_unused());
   chunk_ = new(zone()) LChunk(info(), graph());
-  HPhase phase("Building chunk", chunk_);
+  HPhase phase("L Building chunk", chunk_);
   status_ = BUILDING;
   const ZoneList<HBasicBlock*>* blocks = graph()->blocks();
   for (int i = 0; i < blocks->length(); i++) {
     HBasicBlock* next = NULL;
     if (i < blocks->length() - 1) next = blocks->at(i + 1);
     DoBasicBlock(blocks->at(i), next);
     if (is_aborted()) return NULL;
   }
   status_ = DONE;
   return chunk_;
@@ skipping 1768 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64