PPC: Fix I32AtomicCompareExchange

R=joransiu@ca.ibm.com

Change-Id: Icfbd76b8da133bf39960f1c172cd872876e2cf3e
Reviewed-on: https://chromium-review.googlesource.com/1225672Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#55879}

src/compiler/ppc/code-generator-ppc.cc

@@ -691,7 +691,7 @@ void EmitWordLoadPoisoningIfNeeded(CodeGenerator* codegen, Instruction* instr,
     Label exit;                                                                \
     __ bind(&loop);                                                            \
     __ load_inst(i.OutputRegister(), operand);                                 \
-    __ cmp_inst(i.OutputRegister(), i.InputRegister(2));                       \
+    __ cmp_inst(i.OutputRegister(), i.InputRegister(2), cr0);                  \
     __ bne(&exit, cr0);                                                        \
     __ store_inst(i.InputRegister(3), operand);                                \
     __ bne(&loop, cr0);                                                        \