[turbofan] Fix optimized lowering of Math.imul.

src/compiler/typer.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/typer.h"
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/common-operator.h"
@@ skipping 1727 matching lines @@
 
 Type* Typer::Visitor::TypeNumberShiftRight(Node* node) {
   return Type::Signed32();
 }
 
 
 Type* Typer::Visitor::TypeNumberShiftRightLogical(Node* node) {
   return Type::Unsigned32();
 }
 
+Type* Typer::Visitor::TypeNumberImul(Node* node) { return Type::Signed32(); }
+
 Type* Typer::Visitor::TypeNumberClz32(Node* node) {
   return typer_->cache_.kZeroToThirtyTwo;
 }
 
 Type* Typer::Visitor::TypeNumberCeil(Node* node) {
   return TypeUnaryOp(node, NumberCeil);
 }
 
 Type* Typer::Visitor::TypeNumberFloor(Node* node) {
   return TypeUnaryOp(node, NumberFloor);
@@ skipping 813 matching lines @@
   }
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8