PPC/s390: [arm] Fix infinite loop in Math.pow(2,2147483648).

Port e83739c0

    Fix applies to PPC/s390 as well.

R=jacob.bramley@arm.com, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=v8:5214
LOG=N

Review-Url: https://codereview.chromium.org/2167273003
Cr-Commit-Position: refs/heads/master@{#37956}

src/ppc/code-stubs-ppc.cc

@@ -805,7 +805,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   __ beq(&no_carry, cr0);
   __ fmul(double_result, double_result, double_scratch);
   __ bind(&no_carry);
-  __ ShiftRightArithImm(scratch, scratch, 1, SetRC);
+  __ ShiftRightImm(scratch, scratch, Operand(1), SetRC);
   __ beq(&loop_end, cr0);
   __ fmul(double_scratch, double_scratch, double_scratch);
   __ b(&while_true);

src/s390/code-stubs-s390.cc

@@ -776,7 +776,8 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   __ beq(&no_carry, Label::kNear);
   __ mdbr(double_result, double_scratch);
   __ bind(&no_carry);
-  __ ShiftRightArithP(scratch, scratch, Operand(1));
+  __ ShiftRightP(scratch, scratch, Operand(1));
+  __ LoadAndTestP(scratch, scratch);
   __ beq(&loop_end, Label::kNear);
   __ mdbr(double_scratch, double_scratch);
   __ b(&while_true);