PPC/s390: SmiUntag only for 32bit

R=joransiu@ca.ibm.com, jyan@ca.ibm.com
BUG=
LOG=n

Review-Url: https://codereview.chromium.org/2842843005
Cr-Commit-Position: refs/heads/master@{#44908}

src/builtins/ppc/builtins-ppc.cc

@@ -2208,7 +2208,9 @@ void Builtins::Generate_CallForwardVarargs(MacroAssembler* masm,
   __ bind(&arguments_done);
 
   Label stack_empty, stack_done, stack_overflow;
+#if !V8_TARGET_ARCH_PPC64
   __ SmiUntag(r3);
+#endif
   __ sub(r3, r3, r5);
   __ cmpi(r3, Operand::Zero());
   __ ble(&stack_empty);

src/builtins/s390/builtins-s390.cc

@@ -2218,7 +2218,9 @@ void Builtins::Generate_CallForwardVarargs(MacroAssembler* masm,
   __ 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);