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Unified Diff: src/ia32/full-codegen-ia32.cc

Issue 10909007: Sharing of descriptor arrays. (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: Addressed comments Created 8 years, 3 months ago
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Index: src/ia32/full-codegen-ia32.cc
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index de8e490d2873c87cc4c43c46b7326eafcb0411fb..84b8261d0e792bab33c96c820a48a6a51df43b8c 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -2669,22 +2669,28 @@ void FullCodeGenerator::EmitIsStringWrapperSafeForDefaultValueOf(
__ j(equal, if_false);
// Look for valueOf symbol in the descriptor array, and indicate false if
- // found. The type is not checked, so if it is a transition it is a false
- // negative.
+ // found. Since we omit an enumeration index check, if it is added via a
+ // transition that shares its descriptor array, this is a false positive.
+ Label entry, loop, done;
+
+ // Skip loop if no descriptors are valid.
+ __ NumberOfOwnDescriptors(ecx, ebx);
+ __ cmp(ecx, 0);
+ __ j(equal, &done);
+
__ LoadInstanceDescriptors(ebx, ebx);
- __ mov(ecx, FieldOperand(ebx, FixedArray::kLengthOffset));
- // ebx: descriptor array
- // ecx: length of descriptor array
+ // ebx: descriptor array.
+ // ecx: valid entries in the descriptor array.
// Calculate the end of the descriptor array.
STATIC_ASSERT(kSmiTag == 0);
STATIC_ASSERT(kSmiTagSize == 1);
STATIC_ASSERT(kPointerSize == 4);
- __ lea(ecx, Operand(ebx, ecx, times_2, FixedArray::kHeaderSize));
+ __ imul(ecx, ecx, DescriptorArray::kDescriptorSize);
+ __ lea(ecx, Operand(ebx, ecx, times_2, DescriptorArray::kFirstOffset));
// Calculate location of the first key name.
__ add(ebx, Immediate(DescriptorArray::kFirstOffset));
// Loop through all the keys in the descriptor array. If one of these is the
// symbol valueOf the result is false.
- Label entry, loop;
__ jmp(&entry);
__ bind(&loop);
__ mov(edx, FieldOperand(ebx, 0));
@@ -2695,10 +2701,12 @@ void FullCodeGenerator::EmitIsStringWrapperSafeForDefaultValueOf(
__ cmp(ebx, ecx);
__ j(not_equal, &loop);
+ __ bind(&done);
+
// Reload map as register ebx was used as temporary above.
__ mov(ebx, FieldOperand(eax, HeapObject::kMapOffset));
- // If a valueOf property is not found on the object check that it's
+ // If a valueOf property is not found on the object check that its
// prototype is the un-modified String prototype. If not result is false.
__ mov(ecx, FieldOperand(ebx, Map::kPrototypeOffset));
__ JumpIfSmi(ecx, if_false);
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