[turbofan] Introduce integer multiplication with overflow.

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 797 matching lines @@
                                      (rep == MachineRepresentation::kWord16 &&
                                       m.right().IsInRange(1, 16)))) {
         Int32BinopMatcher mleft(m.left().node());
         if (mleft.right().Is(m.right().Value())) {
           node->ReplaceInput(value_input, mleft.left().node());
           return Changed(node);
         }
       }
       break;
     }
+    // TODO(mvstanton): put kInt32MulWithOverflow here too, eh?

[Benedikt Meurer, 2016/07/12 04:09:28]

Nope, that doesn't make sense. The rules for the shift/and above are unnecessary
extensions/truncations.

[mvstanton, 2016/07/12 08:52:49]

Done.

     default:
       break;
   }
   return NoChange();
 }
 
 
 Reduction MachineOperatorReducer::ReduceProjection(size_t index, Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kInt32AddWithOverflow: {
@@ skipping 382 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8