Optimize redundant HCompareMap instructions with known successors.

R=ishell@chromium.org

Review URL: https://codereview.chromium.org/150663005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19094 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index e670d34..38509a6 100644 (file)
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -942,6 +942,9 @@ LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
+  LInstruction* goto_instr = CheckElideControlInstruction(instr);
+  if (goto_instr != NULL) return goto_instr;
+
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   LOperand* temp = TempRegister();

diff --git a/src/hydrogen-check-elimination.cc b/src/hydrogen-check-elimination.cc
index cd002a1..e12f14a 100644 (file)
--- a/src/hydrogen-check-elimination.cc
+++ b/src/hydrogen-check-elimination.cc
@@ -341,11 +341,15 @@ class HCheckTable : public ZoneObject {
     if (maps == NULL) return;
     if (maps->Contains(instr->map())) {
       if (maps->size() == 1) {
-        // TODO(titzer): replace with goto true branch
+        TRACE(("Marking redundant CompareMap #%d at B%d as true\n",
+            instr->id(), instr->block()->block_id()));
+        instr->set_known_successor_index(0);
         INC_STAT(compares_true_);
       }
     } else {
-      // TODO(titzer): replace with goto false branch
+      TRACE(("Marking redundant CompareMap #%d at B%d as false\n",
+          instr->id(), instr->block()->block_id()));
+      instr->set_known_successor_index(1);
       INC_STAT(compares_false_);
     }
   }

diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 8f1c62b..c25dff1 100644 (file)
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1117,6 +1117,11 @@ void HCompareMap::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
   stream->Add(" (%p)", *map().handle());
   HControlInstruction::PrintDataTo(stream);
+  if (known_successor_index() == 0) {
+    stream->Add(" [true]");
+  } else if (known_successor_index() == 1) {
+    stream->Add(" [false]");
+  }
 }
 
 

diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index cfd5444..a6da1c3 100644 (file)
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -1529,8 +1529,23 @@ class HCompareMap V8_FINAL : public HUnaryControlInstruction {
   DECLARE_INSTRUCTION_FACTORY_P4(HCompareMap, HValue*, Handle<Map>,
                                  HBasicBlock*, HBasicBlock*);
 
+  virtual bool KnownSuccessorBlock(HBasicBlock** block) V8_OVERRIDE {
+    if (known_successor_index() != kNoKnownSuccessorIndex) {
+      *block = SuccessorAt(known_successor_index());
+      return true;
+    }
+    *block = NULL;
+    return false;
+  }
+
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
+  static const int kNoKnownSuccessorIndex = -1;
+  int known_successor_index() const { return known_successor_index_; }
+  void set_known_successor_index(int known_successor_index) {
+    known_successor_index_ = known_successor_index;
+  }
+
   Unique<Map> map() const { return map_; }
 
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
@@ -1548,10 +1563,11 @@ class HCompareMap V8_FINAL : public HUnaryControlInstruction {
               HBasicBlock* true_target = NULL,
               HBasicBlock* false_target = NULL)
       : HUnaryControlInstruction(value, true_target, false_target),
-        map_(Unique<Map>(map)) {
+        known_successor_index_(kNoKnownSuccessorIndex), map_(Unique<Map>(map)) {
     ASSERT(!map.is_null());
   }
 
+  int known_successor_index_;
   Unique<Map> map_;
 };
 

diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 4ebcb30..27a5672 100644 (file)
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1027,6 +1027,9 @@ LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
+  LInstruction* goto_instr = CheckElideControlInstruction(instr);
+  if (goto_instr != NULL) return goto_instr;
+
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   return new(zone()) LCmpMapAndBranch(value);

diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 6b1b982..bb8e750 100644 (file)
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -945,6 +945,9 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
+  LInstruction* goto_instr = CheckElideControlInstruction(instr);
+  if (goto_instr != NULL) return goto_instr;
+
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   LOperand* temp = TempRegister();

diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 3c9eb2d..666b688 100644 (file)
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -952,6 +952,9 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
+  LInstruction* goto_instr = CheckElideControlInstruction(instr);
+  if (goto_instr != NULL) return goto_instr;
+
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   return new(zone()) LCmpMapAndBranch(value);