[Turbofan]: Eliminate the check for -0 if it's not possible/observable.

src/compiler/simplified-operator.h

 // 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.
 
 #ifndef V8_COMPILER_SIMPLIFIED_OPERATOR_H_
 #define V8_COMPILER_SIMPLIFIED_OPERATOR_H_
 
 #include <iosfwd>
 
 #include "src/compiler/operator.h"
@@ skipping 111 matching lines @@
   kNeverReturnHole,        // Never return the hole (deoptimize instead).
   kConvertHoleToUndefined  // Convert the hole to undefined.
 };
 
 size_t hash_value(CheckTaggedHoleMode);
 
 std::ostream& operator<<(std::ostream&, CheckTaggedHoleMode);
 
 CheckTaggedHoleMode CheckTaggedHoleModeOf(const Operator*) WARN_UNUSED_RESULT;
 
+enum class CheckForMinusZeroMode : uint8_t {
+  kCheckForMinusZero,
+  kDontCheckForMinusZero,
+};
+
+size_t hash_value(CheckForMinusZeroMode);
+
+std::ostream& operator<<(std::ostream&, CheckForMinusZeroMode);
+
+CheckForMinusZeroMode CheckMinusZeroModeOf(const Operator*) WARN_UNUSED_RESULT;
+
 Type* TypeOf(const Operator* op) WARN_UNUSED_RESULT;
 
 BinaryOperationHints::Hint BinaryOperationHintOf(const Operator* op);
 
 CompareOperationHints::Hint CompareOperationHintOf(const Operator* op);
 
 // Interface for building simplified operators, which represent the
 // medium-level operations of V8, including adding numbers, allocating objects,
 // indexing into objects and arrays, etc.
 // All operators are typed but many are representation independent.
@@ skipping 112 matching lines @@
   const Operator* CheckNumber();
   const Operator* CheckTaggedPointer();
   const Operator* CheckTaggedSigned();
 
   const Operator* CheckedInt32Add();
   const Operator* CheckedInt32Sub();
   const Operator* CheckedInt32Div();
   const Operator* CheckedInt32Mod();
   const Operator* CheckedUint32Div();
   const Operator* CheckedUint32Mod();
-  const Operator* CheckedInt32Mul();
+  const Operator* CheckedInt32Mul(CheckForMinusZeroMode);
   const Operator* CheckedUint32ToInt32();
   const Operator* CheckedFloat64ToInt32();
   const Operator* CheckedTaggedToInt32();
   const Operator* CheckedTaggedToFloat64();
 
   const Operator* CheckFloat64Hole(CheckFloat64HoleMode);
   const Operator* CheckTaggedHole(CheckTaggedHoleMode);
 
   const Operator* ObjectIsCallable();
   const Operator* ObjectIsNumber();
@@ skipping 26 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(SimplifiedOperatorBuilder);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_SIMPLIFIED_OPERATOR_H_