Fix constant offset check for inlined write barrier to work in cases when offset...

Review URL: http://codereview.chromium.org/1646008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4431 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 2d7be9d..7a9bcf0 100644 (file)
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -143,7 +143,17 @@ void MacroAssembler::RecordWrite(Register object, int offset,
 
   InNewSpace(object, value, equal, &done);
 
-  if ((offset > 0) && (offset < Page::kMaxHeapObjectSize)) {
+  // The offset is relative to a tagged or untagged HeapObject pointer,
+  // so either offset or offset + kHeapObjectTag must be a
+  // multiple of kPointerSize.
+  ASSERT(IsAligned(offset, kPointerSize) ||
+         IsAligned(offset + kHeapObjectTag, kPointerSize));
+
+  // We use optimized write barrier code if the word being written to is not in
+  // a large object chunk or is in the first page of a large object chunk.
+  // We make sure that an offset is inside the right limits whether it is
+  // tagged or untagged.
+  if ((offset > 0) && (offset < Page::kMaxHeapObjectSize - kHeapObjectTag)) {
     // Compute the bit offset in the remembered set, leave it in 'value'.
     lea(value, Operand(object, offset));
     and_(value, Page::kPageAlignmentMask);

diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 3e8dec6..e9aa7a2 100644 (file)
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -226,7 +226,17 @@ void MacroAssembler::RecordWriteNonSmi(Register object,
   cmpq(scratch, kScratchRegister);
   j(equal, &done);
 
-  if ((offset > 0) && (offset < Page::kMaxHeapObjectSize)) {
+  // The offset is relative to a tagged or untagged HeapObject pointer,
+  // so either offset or offset + kHeapObjectTag must be a
+  // multiple of kPointerSize.
+  ASSERT(IsAligned(offset, kPointerSize) ||
+         IsAligned(offset + kHeapObjectTag, kPointerSize));
+
+  // We use optimized write barrier code if the word being written to is not in
+  // a large object page, or is in the first "page" of a large object page.
+  // We make sure that an offset is inside the right limits whether it is
+  // tagged or untagged.
+  if ((offset > 0) && (offset < Page::kMaxHeapObjectSize - kHeapObjectTag)) {
     // Compute the bit offset in the remembered set, leave it in 'value'.
     lea(scratch, Operand(object, offset));
     ASSERT(is_int32(Page::kPageAlignmentMask));