[turbofan] Fix optimized lowering of Math.imul.

src/compiler/representation-change.cc

 // Copyright 2015 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/representation-change.h"
 
 #include <sstream>
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 473 matching lines @@
     case IrOpcode::kNumberModulus:
       return machine()->Uint32Mod();
     case IrOpcode::kNumberEqual:
       return machine()->Word32Equal();
     case IrOpcode::kNumberLessThan:
       return machine()->Uint32LessThan();
     case IrOpcode::kNumberLessThanOrEqual:
       return machine()->Uint32LessThanOrEqual();
     case IrOpcode::kNumberClz32:
       return machine()->Word32Clz();
+    case IrOpcode::kNumberImul:
+      return machine()->Int32Mul();
     default:
       UNREACHABLE();
       return nullptr;
   }
 }
 
 
 const Operator* RepresentationChanger::Float64OperatorFor(
     IrOpcode::Value opcode) {
   switch (opcode) {
@@ skipping 62 matching lines @@
 }
 
 Node* RepresentationChanger::InsertChangeTaggedToFloat64(Node* node) {
   return jsgraph()->graph()->NewNode(simplified()->ChangeTaggedToFloat64(),
                                      node);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8