[v8-dev] [v8] r10870 committed - Eliminate overflow check after integer add and sub operation if result...

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Revision: 10870
Author:   fschnei...@chromium.org
Date:     Wed Feb 29 05:41:18 2012
Log:      Eliminate overflow check after integer add and sub operation if  
result is truncated to int32.
Review URL: https://chromiumcodereview.appspot.com/9286002
http://code.google.com/p/v8/source/detail?r=10870
Modified:
 /branches/bleeding_edge/src/hydrogen-instructions.cc
 /branches/bleeding_edge/src/hydrogen-instructions.h
 /branches/bleeding_edge/src/hydrogen.cc

=======================================
--- /branches/bleeding_edge/src/hydrogen-instructions.cc	Tue Feb 28  
07:32:58 2012
+++ /branches/bleeding_edge/src/hydrogen-instructions.cc	Wed Feb 29  
05:41:18 2012
@@ -283,6 +283,14 @@
   }
   return tail_;
 }
+
+
+bool HValue::CheckUsesForFlag(Flag f) {
+  for (HUseIterator it(uses()); !it.Done(); it.Advance()) {
+    if (!it.value()->CheckFlag(f)) return false;
+  }
+  return true;
+}


 HUseIterator::HUseIterator(HUseListNode* head) : next_(head) {
@@ -831,12 +839,12 @@


 HValue* HConstant::Canonicalize() {
-  return HasNoUses() && !IsBlockEntry() ? NULL : this;
+  return HasNoUses() ? NULL : this;
 }


 HValue* HTypeof::Canonicalize() {
-  return HasNoUses() && !IsBlockEntry() ? NULL : this;
+  return HasNoUses() ? NULL : this;
 }


@@ -856,6 +864,20 @@
   }
   return this;
 }
+
+
+HValue* HAdd::Canonicalize() {
+  if (!representation().IsInteger32()) return this;
+  if (CheckUsesForFlag(kTruncatingToInt32)) ClearFlag(kCanOverflow);
+  return this;
+}
+
+
+HValue* HSub::Canonicalize() {
+  if (!representation().IsInteger32()) return this;
+  if (CheckUsesForFlag(kTruncatingToInt32)) ClearFlag(kCanOverflow);
+  return this;
+}


 HValue* HChange::Canonicalize() {
=======================================
--- /branches/bleeding_edge/src/hydrogen-instructions.h	Tue Feb 28 07:32:58  
2012
+++ /branches/bleeding_edge/src/hydrogen-instructions.h	Wed Feb 29 05:41:18  
2012
@@ -644,6 +644,9 @@
   void SetFlag(Flag f) { flags_ |= (1 << f); }
   void ClearFlag(Flag f) { flags_ &= ~(1 << f); }
   bool CheckFlag(Flag f) const { return (flags_ & (1 << f)) != 0; }
+
+  // Returns true if the flag specified is set for all uses, false  
otherwise.
+  bool CheckUsesForFlag(Flag f);

   GVNFlagSet gvn_flags() const { return gvn_flags_; }
   void SetGVNFlag(GVNFlag f) { gvn_flags_.Add(f); }
@@ -823,6 +826,8 @@
   int position() const { return position_; }
   bool has_position() const { return position_ != RelocInfo::kNoPosition; }
   void set_position(int position) { position_ = position; }
+
+  bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }

   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;

@@ -1120,10 +1125,6 @@
   static HUnaryOperation* cast(HValue* value) {
     return reinterpret_cast<HUnaryOperation*>(value);
   }
-
-  virtual bool CanTruncateToInt32() const {
-    return CheckFlag(kTruncatingToInt32);
-  }

   HValue* value() { return OperandAt(0); }
   virtual void PrintDataTo(StringStream* stream);
@@ -1248,15 +1249,12 @@
       : HUnaryOperation(value) {
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
+    SetFlag(kTruncatingToInt32);
   }

   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
-
-  virtual bool CanTruncateToInt32() const {
-    return true;
-  }

   virtual HValue* Canonicalize() {
     if (value()->representation().IsInteger32()) {
@@ -3154,6 +3152,8 @@

   virtual HType CalculateInferredType();

+  virtual HValue* Canonicalize();
+
   DECLARE_CONCRETE_INSTRUCTION(Add)

  protected:
@@ -3172,6 +3172,8 @@

   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);

+  virtual HValue* Canonicalize();
+
   static HInstruction* NewHSub(Zone* zone,
                               HValue* context,
                               HValue* left,
@@ -3257,7 +3259,6 @@

   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);

-
   static HInstruction* NewHDiv(Zone* zone,
                                HValue* context,
                                HValue* left,
=======================================
--- /branches/bleeding_edge/src/hydrogen.cc     Wed Feb 29 04:12:52 2012
+++ /branches/bleeding_edge/src/hydrogen.cc     Wed Feb 29 05:41:18 2012
@@ -2067,13 +2067,9 @@
     for (int i = 0; i < phi_list()->length(); i++) {
       HPhi* phi = phi_list()->at(i);
       if (!phi->CheckFlag(HValue::kTruncatingToInt32)) continue;
-      for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
-        HValue* use = it.value();
-        if (!use->CheckFlag(HValue::kTruncatingToInt32)) {
-          phi->ClearFlag(HValue::kTruncatingToInt32);
-          change = true;
-          break;
-        }
+      if (!phi->CheckUsesForFlag(HValue::kTruncatingToInt32)) {
+        phi->ClearFlag(HValue::kTruncatingToInt32);
+        change = true;
       }
     }
   }

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