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

src/arm64/macro-assembler-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 4014 matching lines @@
 
   // Load store buffer top.
   Mov(scratch2, ExternalReference::store_buffer_top(isolate()));
   Ldr(scratch1, MemOperand(scratch2));
   // Store pointer to buffer and increment buffer top.
   Str(address, MemOperand(scratch1, kPointerSize, PostIndex));
   // Write back new top of buffer.
   Str(scratch1, MemOperand(scratch2));
   // Call stub on end of buffer.
   // Check for end of buffer.
-  DCHECK(StoreBuffer::kStoreBufferOverflowBit ==
-         (1 << (14 + kPointerSizeLog2)));
+  Tst(scratch1, StoreBuffer::kStoreBufferMask);
   if (and_then == kFallThroughAtEnd) {
-    Tbz(scratch1, (14 + kPointerSizeLog2), &done);
+    B(ne, &done);
   } else {
     DCHECK(and_then == kReturnAtEnd);
-    Tbnz(scratch1, (14 + kPointerSizeLog2), &store_buffer_overflow);
+    B(eq, &store_buffer_overflow);
     Ret();
   }
 
   Bind(&store_buffer_overflow);
   Push(lr);
   StoreBufferOverflowStub store_buffer_overflow_stub(isolate(), fp_mode);
   CallStub(&store_buffer_overflow_stub);
   Pop(lr);
 
   Bind(&done);
@@ skipping 1041 matching lines @@
 }
 
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64