Fix for issue 2132.

src/hydrogen-instructions.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 504 matching lines @@
 
 
 void HValue::RemoveLastAddedRange() {
   ASSERT(HasRange());
   ASSERT(range_->next() != NULL);
   range_ = range_->next();
 }
 
 
 void HValue::ComputeInitialRange(Zone* zone) {
-  ASSERT(!HasRange());
-  range_ = InferRange(zone);
+  ASSERT(CheckFlag(kHasPreinitializedRange) || !HasRange());
+  Range* new_range = InferRange(zone);
+  if (CheckFlag(kHasPreinitializedRange)) {
+    range_->Intersect(new_range);
+    ClearFlag(kHasPreinitializedRange);
+  } else {
+    range_ = new_range;
+  }
   ASSERT(HasRange());
 }
 
+
+void HValue::PreinitializeRange(Zone* zone) {
+  ASSERT(!HasRange());
+  range_ = new(zone) Range();
+  range_->set_can_be_minus_zero(true);
+  SetFlag(kHasPreinitializedRange);
+  ASSERT(HasRange());
+}
+
 
 void HInstruction::PrintTo(StringStream* stream) {
   PrintMnemonicTo(stream);
   PrintDataTo(stream);
   PrintRangeTo(stream);
   PrintChangesTo(stream);
   PrintTypeTo(stream);
 }
 
 
@@ skipping 314 matching lines @@
 }
 
 
 HValue* HBitwise::Canonicalize() {
   if (!representation().IsInteger32()) return this;
   // If x is an int32, then x & -1 == x, x | 0 == x and x ^ 0 == x.
   int32_t nop_constant = (op() == Token::BIT_AND) ? -1 : 0;
   if (left()->IsConstant() &&
       HConstant::cast(left())->HasInteger32Value() &&
       HConstant::cast(left())->Integer32Value() == nop_constant) {
+    right()->PreinitializeRange(block()->zone());
+    right()->range()->set_can_be_minus_zero(false);

[Vyacheslav Egorov (Chromium), 2012/05/18 17:39:05]

I don't think this is correct. Consider code like:

function mul(a, b) {
  var x = a * b;
  x | 0;
  return x;
}

your code will remove minus zero from the range of x but this is incorrect.

     return right();
   }
   if (right()->IsConstant() &&
       HConstant::cast(right())->HasInteger32Value() &&
       HConstant::cast(right())->Integer32Value() == nop_constant) {
+    left()->PreinitializeRange(block()->zone());
+    left()->range()->set_can_be_minus_zero(false);
     return left();
   }
   return this;
 }
 
 
 HValue* HBitNot::Canonicalize() {
   // Optimize ~~x, a common pattern used for ToInt32(x).
   if (value()->IsBitNot()) {
     HValue* result = HBitNot::cast(value())->value();
@@ skipping 1557 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal