[wasm] Remove x / -1 = -x constant folding for wasm

src/compiler/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/compiler/machine-operator-reducer.h"
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/base/ieee754.h"
 #include "src/codegen.h"
@@ skipping 419 matching lines @@
         // Do some calculation to make a signalling NaN quiet.
         return ReplaceFloat64(m.right().Value() - m.right().Value());
       }
       if (m.left().IsNaN()) {  // NaN / x => NaN
         // Do some calculation to make a signalling NaN quiet.
         return ReplaceFloat64(m.left().Value() - m.left().Value());
       }
       if (m.IsFoldable()) {  // K / K => K
         return ReplaceFloat64(m.left().Value() / m.right().Value());
       }
-      if (m.right().Is(-1)) {  // x / -1.0 => -x
+      if (!wasm_origin_ && m.right().Is(-1)) {  // x / -1.0 => -x

[titzer, 2017/01/31 17:24:49]

Can we rename this option to something closer to what it means, e.g.
"preserve_nan_bits" or something similar?

[ahaas, 2017/01/31 19:43:37]

Done with the rebasing.

         node->RemoveInput(1);
         NodeProperties::ChangeOp(node, machine()->Float64Neg());
         return Changed(node);
       }
       if (m.right().IsNormal() && m.right().IsPositiveOrNegativePowerOf2()) {
         // All reciprocals of non-denormal powers of two can be represented
         // exactly, so division by power of two can be reduced to
         // multiplication by reciprocal, with the same result.
         node->ReplaceInput(1, Float64Constant(1.0 / m.right().Value()));
         NodeProperties::ChangeOp(node, machine()->Float64Mul());
@@ skipping 972 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8