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

src/ppc/macro-assembler-ppc.cc

 // Copyright 2014 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.
 
 #include <assert.h>  // For assert
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/base/bits.h"
@@ skipping 552 matching lines @@
       ExternalReference::store_buffer_top(isolate());
   mov(ip, Operand(store_buffer));
   LoadP(scratch, MemOperand(ip));
   // Store pointer to buffer and increment buffer top.
   StoreP(address, MemOperand(scratch));
   addi(scratch, scratch, Operand(kPointerSize));
   // Write back new top of buffer.
   StoreP(scratch, MemOperand(ip));
   // Call stub on end of buffer.
   // Check for end of buffer.
-  mov(r0, Operand(StoreBuffer::kStoreBufferOverflowBit));
+  mov(r0, Operand(StoreBuffer::kStoreBufferMask));
   and_(r0, scratch, r0, SetRC);
 
   if (and_then == kFallThroughAtEnd) {
-    beq(&done, cr0);
+    bne(&done, cr0);
   } else {
     DCHECK(and_then == kReturnAtEnd);
-    Ret(eq, cr0);
+    Ret(ne, cr0);
   }
   mflr(r0);
   push(r0);
   StoreBufferOverflowStub store_buffer_overflow(isolate(), fp_mode);
   CallStub(&store_buffer_overflow);
   pop(r0);
   mtlr(r0);
   bind(&done);
   if (and_then == kReturnAtEnd) {
     Ret();
@@ skipping 4050 matching lines @@
   }
   if (mag.shift > 0) srawi(result, result, mag.shift);
   ExtractBit(r0, dividend, 31);
   add(result, result, r0);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_PPC