Bug 1471361: Keep stack height constant when fastpathing truncation r=tcampbell

--HG--
extra : rebase_source : b2f2238e73a1c24ce3b926dd76d147feef5a0ddf

js/src/jit/CacheIRCompiler.cpp

@@ -1932,13 +1932,13 @@ CacheIRCompiler::emitTruncateDoubleToUInt32()
     ValueOperand val = allocator.useValueRegister(masm, reader.valOperandId());
     Register res = allocator.defineRegister(masm, reader.int32OperandId());
 
+    Label int32, done;
+    masm.branchTestInt32(Assembler::Equal, val, &int32);
+
     Label doneTruncate,  truncateABICall;
     if (mode_ != Mode::Baseline)
         masm.push(FloatReg0);
 
-    Label int32, done;
-    masm.branchTestInt32(Assembler::Equal, val, &int32);
-
     masm.unboxDouble(val, FloatReg0);
     masm.branchTruncateDoubleMaybeModUint32(FloatReg0, res, &truncateABICall);
     masm.jump(&doneTruncate);