X87: [turbofan] avoid xchg instruction on Intel.

src/x87/code-stubs-x87.cc

 // Copyright 2012 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_X87
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 3033 matching lines @@
   __ JumpIfNotRoot(ecx, Heap::kBooleanMapRootIndex, &miss, miss_distance);
   __ JumpIfNotRoot(ebx, Heap::kBooleanMapRootIndex, &miss, miss_distance);
   if (op() != Token::EQ_STRICT && is_strong(strength())) {
     __ TailCallRuntime(Runtime::kThrowStrongModeImplicitConversion);
   } else {
     if (!Token::IsEqualityOp(op())) {
       __ mov(eax, FieldOperand(eax, Oddball::kToNumberOffset));
       __ AssertSmi(eax);
       __ mov(edx, FieldOperand(edx, Oddball::kToNumberOffset));
       __ AssertSmi(edx);
-      __ xchg(eax, edx);
+      __ push(eax);
+      __ mov(eax, edx);
+      __ pop(edx);
     }
     __ sub(eax, edx);
     __ Ret();
   }
 
   __ bind(&miss);
   GenerateMiss(masm);
 }
 
 
@@ skipping 2285 matching lines @@
                            Operand(ebp, 7 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X87