Use the macro assembler Set instead of explicit xor for clearing registers.

src/ia32/code-stubs-ia32.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 86 matching lines @@
 
   // Get the function from the stack.
   __ mov(ecx, Operand(esp, 1 * kPointerSize));
 
   // Setup the object header.
   __ mov(FieldOperand(eax, HeapObject::kMapOffset), Factory::context_map());
   __ mov(FieldOperand(eax, Context::kLengthOffset),
          Immediate(Smi::FromInt(length)));
 
   // Setup the fixed slots.
-  __ xor_(ebx, Operand(ebx));  // Set to NULL.
+  __ Set(ebx, Immediate(0));  // Set to NULL.
   __ mov(Operand(eax, Context::SlotOffset(Context::CLOSURE_INDEX)), ecx);
   __ mov(Operand(eax, Context::SlotOffset(Context::FCONTEXT_INDEX)), eax);
   __ mov(Operand(eax, Context::SlotOffset(Context::PREVIOUS_INDEX)), ebx);
   __ mov(Operand(eax, Context::SlotOffset(Context::EXTENSION_INDEX)), ebx);
 
   // Copy the global object from the surrounding context. We go through the
   // context in the function (ecx) to match the allocation behavior we have
   // in the runtime system (see Heap::AllocateFunctionContext).
   __ mov(ebx, FieldOperand(ecx, JSFunction::kContextOffset));
   __ mov(ebx, Operand(ebx, Context::SlotOffset(Context::GLOBAL_INDEX)));
@@ skipping 4178 matching lines @@
       // The representation of NaN values has all exponent bits (52..62) set,
       // and not all mantissa bits (0..51) clear.
       // We only accept QNaNs, which have bit 51 set.
       // Read top bits of double representation (second word of value).
 
       // Value is a QNaN if value & kQuietNaNMask == kQuietNaNMask, i.e.,
       // all bits in the mask are set. We only need to check the word
       // that contains the exponent and high bit of the mantissa.
       STATIC_ASSERT(((kQuietNaNHighBitsMask << 1) & 0x80000000u) != 0);
       __ mov(edx, FieldOperand(edx, HeapNumber::kExponentOffset));
-      __ xor_(eax, Operand(eax));
+      __ Set(eax, Immediate(0));
       // Shift value and mask so kQuietNaNHighBitsMask applies to topmost
       // bits.
       __ add(edx, Operand(edx));
       __ cmp(edx, kQuietNaNHighBitsMask << 1);
       if (cc_ == equal) {
         STATIC_ASSERT(EQUAL != 1);
         __ setcc(above_equal, eax);
         __ ret(0);
       } else {
         NearLabel nan;
@@ skipping 109 matching lines @@
       __ FCmp();
 
       // Don't base result on EFLAGS when a NaN is involved.
       __ j(parity_even, &unordered, not_taken);
 
       NearLabel below_label, above_label;
       // Return a result of -1, 0, or 1, based on EFLAGS.
       __ j(below, &below_label, not_taken);
       __ j(above, &above_label, not_taken);
 
-      __ xor_(eax, Operand(eax));
+      __ Set(eax, Immediate(0));
       __ ret(0);
 
       __ bind(&below_label);
       __ mov(eax, Immediate(Smi::FromInt(-1)));
       __ ret(0);
 
       __ bind(&above_label);
       __ mov(eax, Immediate(Smi::FromInt(1)));
       __ ret(0);
     }
@@ skipping 192 matching lines @@
   // Restore next handler and frame pointer, discard handler state.
   STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   __ pop(Operand::StaticVariable(handler_address));
   STATIC_ASSERT(StackHandlerConstants::kFPOffset == 1 * kPointerSize);
   __ pop(ebp);
   __ pop(edx);  // Remove state.
 
   // Before returning we restore the context from the frame pointer if
   // not NULL.  The frame pointer is NULL in the exception handler of
   // a JS entry frame.
-  __ xor_(esi, Operand(esi));  // Tentatively set context pointer to NULL.
+  __ Set(esi, Immediate(0));  // Tentatively set context pointer to NULL.
   NearLabel skip;
   __ cmp(ebp, 0);
   __ j(equal, &skip, not_taken);
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
   __ bind(&skip);
 
   STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   __ ret(0);
 }
 
@@ skipping 132 matching lines @@
     __ mov(eax, false);
     __ mov(Operand::StaticVariable(external_caught), eax);
 
     // Set pending exception and eax to out of memory exception.
     ExternalReference pending_exception(Top::k_pending_exception_address);
     __ mov(eax, reinterpret_cast<int32_t>(Failure::OutOfMemoryException()));
     __ mov(Operand::StaticVariable(pending_exception), eax);
   }
 
   // Clear the context pointer.
-  __ xor_(esi, Operand(esi));
+  __ Set(esi, Immediate(0));
 
   // Restore fp from handler and discard handler state.
   STATIC_ASSERT(StackHandlerConstants::kFPOffset == 1 * kPointerSize);
   __ pop(ebp);
   __ pop(edx);  // State.
 
   STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   __ ret(0);
 }
 
@@ skipping 1592 matching lines @@
   // Do a tail call to the rewritten stub.
   __ jmp(Operand(edi));
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32