S390: Fix Register conflict in CEntryStub

src/s390/code-stubs-s390.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.
 
 #if V8_TARGET_ARCH_S390
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 1086 matching lines @@
   Label exception_returned;
   __ CompareRoot(r2, Heap::kExceptionRootIndex);
   __ beq(&exception_returned, Label::kNear);
 
   // Check that there is no pending exception, otherwise we
   // should have returned the exception sentinel.
   if (FLAG_debug_code) {
     Label okay;
     ExternalReference pending_exception_address(
         Isolate::kPendingExceptionAddress, isolate());
-    __ mov(r4, Operand(pending_exception_address));
-    __ LoadP(r4, MemOperand(r4));
-    __ CompareRoot(r4, Heap::kTheHoleValueRootIndex);
+    __ mov(r1, Operand(pending_exception_address));
+    __ LoadP(r1, MemOperand(r1));
+    __ CompareRoot(r1, Heap::kTheHoleValueRootIndex);
     // Cannot use check here as it attempts to generate call into runtime.
     __ beq(&okay, Label::kNear);
     __ stop("Unexpected pending exception");
     __ bind(&okay);
   }
 
   // Exit C frame and return.
   // r2:r3: result
   // sp: stack pointer
   // fp: frame pointer
@@ skipping 4594 matching lines @@
   CallApiFunctionAndReturn(masm, api_function_address, thunk_ref,
                            kStackUnwindSpace, NULL, return_value_operand, NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_S390