Reland of PPC/s390: SmiUntag only for 32bit

src/builtins/s390/builtins-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/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 2196 matching lines @@
     __ LoadP(r2, FieldMemOperand(r2, JSFunction::kSharedFunctionInfoOffset));
     __ LoadW(r2, FieldMemOperand(
                      r2, SharedFunctionInfo::kFormalParameterCountOffset));
     __ LoadRR(r5, fp);
   }
   __ b(&arguments_done);
   __ bind(&arguments_adaptor);
   {
     // Load the length from the ArgumentsAdaptorFrame.
     __ LoadP(r2, MemOperand(r5, ArgumentsAdaptorFrameConstants::kLengthOffset));
+#if V8_TARGET_ARCH_S390X
+    __ SmiUntag(r2);
+#endif
   }
   __ bind(&arguments_done);
 
   Label stack_empty, stack_done, stack_overflow;
+#if !V8_TARGET_ARCH_S390X
   __ SmiUntag(r2);
+#endif
   __ SubP(r2, r2, r4);
   __ CmpP(r2, Operand::Zero());
   __ ble(&stack_empty);
   {
     // Check for stack overflow.
     Generate_StackOverflowCheck(masm, r2, r4, &stack_overflow);
 
     // Forward the arguments from the caller frame.
     {
       Label loop;
@@ skipping 890 matching lines @@
   // Now jump to the instructions of the returned code object.
   __ Jump(ip);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_S390