[wasm] Fix constant folding with signalling NaN.

test/cctest/compiler/test-machine-operator-reducer.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.
 
 #include "src/base/utils/random-number-generator.h"
 #include "src/codegen.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/compiler/operator-properties.h"
 #include "src/compiler/typer.h"
@@ skipping 832 matching lines @@
   R.binop = R.machine.Float32Sub();
 
   FOR_FLOAT32_INPUTS(pl) {
     FOR_FLOAT32_INPUTS(pr) {
       float x = *pl, y = *pr;
       R.CheckFoldBinop<float>(x - y, x, y);
     }
   }
 
   Node* x = R.Parameter();
-  Node* zero = R.Constant<float>(0.0);
   Node* nan = R.Constant<float>(std::numeric_limits<float>::quiet_NaN());
 
-  R.CheckBinop(x, x, zero);   // x - 0 => x
-  R.CheckBinop(nan, nan, x);  // nan - x  => nan
-  R.CheckBinop(nan, x, nan);  // x - nan => nan
+  // nan - x  => nan
+  R.CheckFoldBinop(std::numeric_limits<float>::quiet_NaN(), nan, x);
+  // x - nan => nan
+  R.CheckFoldBinop(std::numeric_limits<float>::quiet_NaN(), x, nan);
 }
 
 TEST(ReduceFloat64Sub) {
   ReducerTester R;
   R.binop = R.machine.Float64Sub();
 
   FOR_FLOAT64_INPUTS(pl) {
     FOR_FLOAT64_INPUTS(pr) {
       double x = *pl, y = *pr;
       R.CheckFoldBinop<double>(x - y, x, y);
     }
   }
 
   Node* x = R.Parameter();
-  Node* zero = R.Constant<double>(0.0);
   Node* nan = R.Constant<double>(std::numeric_limits<double>::quiet_NaN());
 
-  R.CheckBinop(x, x, zero);   // x - 0 => x
-  R.CheckBinop(nan, nan, x);  // nan - x  => nan
-  R.CheckBinop(nan, x, nan);  // x - nan => nan
+  // nan - x  => nan
+  R.CheckFoldBinop(std::numeric_limits<double>::quiet_NaN(), nan, x);
+  // x - nan => nan
+  R.CheckFoldBinop(std::numeric_limits<double>::quiet_NaN(), x, nan);
 }
 
 // TODO(titzer): test MachineOperatorReducer for Word64And
 // TODO(titzer): test MachineOperatorReducer for Word64Or
 // TODO(titzer): test MachineOperatorReducer for Word64Xor
 // TODO(titzer): test MachineOperatorReducer for Word64Equal
 // TODO(titzer): test MachineOperatorReducer for Word64Not
 // TODO(titzer): test MachineOperatorReducer for Int64Mul
 // TODO(titzer): test MachineOperatorReducer for Int64UMul
 // TODO(titzer): test MachineOperatorReducer for Int64Div
 // TODO(titzer): test MachineOperatorReducer for Uint64Div
 // TODO(titzer): test MachineOperatorReducer for Int64Mod
 // TODO(titzer): test MachineOperatorReducer for Uint64Mod
 // TODO(titzer): test MachineOperatorReducer for Int64Neg
 // TODO(titzer): test MachineOperatorReducer for ChangeInt32ToFloat64
 // TODO(titzer): test MachineOperatorReducer for ChangeFloat64ToInt32
 // TODO(titzer): test MachineOperatorReducer for Float64Compare
 // TODO(titzer): test MachineOperatorReducer for Float64Add
 // TODO(titzer): test MachineOperatorReducer for Float64Sub
 // TODO(titzer): test MachineOperatorReducer for Float64Mul
 // TODO(titzer): test MachineOperatorReducer for Float64Div
 // TODO(titzer): test MachineOperatorReducer for Float64Mod
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8