Change store buffer overflow check to not rely on the store buffer being (2*Size) aligned.

src/x87/macro-assembler-x87.cc

Index: src/x87/macro-assembler-x87.cc
diff --git a/src/x87/macro-assembler-x87.cc b/src/x87/macro-assembler-x87.cc
index f8e43ac28afe3c8f3f8bc93bffd64d2b14e0c435..b46167d1f9ae3f6b33e9449c7b1a8280acbe3a05 100644
--- a/src/x87/macro-assembler-x87.cc
+++ b/src/x87/macro-assembler-x87.cc
@@ -196,15 +196,15 @@ void MacroAssembler::RememberedSetHelper(
   mov(Operand::StaticVariable(store_buffer), scratch);
   // Call stub on end of buffer.
   // Check for end of buffer.
-  test(scratch, Immediate(StoreBuffer::kStoreBufferOverflowBit));
+  test(scratch, Immediate(StoreBuffer::kStoreBufferMask));
   if (and_then == kReturnAtEnd) {
     Label buffer_overflowed;
-    j(not_equal, &buffer_overflowed, Label::kNear);
+    j(equal, &buffer_overflowed, Label::kNear);
     ret(0);
     bind(&buffer_overflowed);
   } else {
     DCHECK(and_then == kFallThroughAtEnd);
-    j(equal, &done, Label::kNear);
+    j(not_equal, &done, Label::kNear);
   }
   StoreBufferOverflowStub store_buffer_overflow(isolate(), save_fp);
   CallStub(&store_buffer_overflow);