[turbofan] Remove minus zero check for rhs of CheckedInt32Sub.

src/compiler/simplified-lowering.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/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/address-map.h"
 #include "src/base/bits.h"
@@ skipping 69 matching lines @@
       return MachineRepresentation::kWord32;
     case kExternalFloat32Array:
       return MachineRepresentation::kFloat32;
     case kExternalFloat64Array:
       return MachineRepresentation::kFloat64;
   }
   UNREACHABLE();
   return MachineRepresentation::kNone;
 }
 
-UseInfo CheckedUseInfoAsWord32FromHint(NumberOperationHint hint) {
+UseInfo CheckedUseInfoAsWord32FromHint(
+    NumberOperationHint hint, CheckForMinusZeroMode minus_zero_mode =
+                                  CheckForMinusZeroMode::kCheckForMinusZero) {
   switch (hint) {
     case NumberOperationHint::kSignedSmall:
-      return UseInfo::CheckedSignedSmallAsWord32();
+      return UseInfo::CheckedSignedSmallAsWord32(minus_zero_mode);
     case NumberOperationHint::kSigned32:
-      return UseInfo::CheckedSigned32AsWord32();
+      return UseInfo::CheckedSigned32AsWord32(minus_zero_mode);
     case NumberOperationHint::kNumber:
       return UseInfo::CheckedNumberAsWord32();
     case NumberOperationHint::kNumberOrOddball:
       return UseInfo::CheckedNumberOrOddballAsWord32();
   }
   UNREACHABLE();
   return UseInfo::None();
 }
 
 UseInfo CheckedUseInfoAsFloat64FromHint(NumberOperationHint hint) {
@@ skipping 1033 matching lines @@
           hint == NumberOperationHint::kSigned32) {
         VisitBinop(node, UseInfo::TruncatingWord32(),
                    MachineRepresentation::kWord32, Type::Signed32());
         if (lower()) ChangeToInt32OverflowOp(node);
         return;
       }
     }
 
     if (hint == NumberOperationHint::kSignedSmall ||
         hint == NumberOperationHint::kSigned32) {
-      VisitBinop(node, CheckedUseInfoAsWord32FromHint(hint),
-                 MachineRepresentation::kWord32, Type::Signed32());
+      UseInfo left_use = CheckedUseInfoAsWord32FromHint(hint);
+      // For subtraction, the right hand side can be minus zero without
+      // resulting in minus zero, so we skip the check for it.
+      UseInfo right_use = CheckedUseInfoAsWord32FromHint(
+          hint, node->opcode() == IrOpcode::kSpeculativeNumberSubtract
+                    ? CheckForMinusZeroMode::kDontCheckForMinusZero
+                    : CheckForMinusZeroMode::kCheckForMinusZero);
+      VisitBinop(node, left_use, right_use, MachineRepresentation::kWord32,
+                 Type::Signed32());
       if (lower()) ChangeToInt32OverflowOp(node);
       return;
     }
 
     // default case => Float64Add/Sub
     VisitBinop(node, UseInfo::CheckedNumberOrOddballAsFloat64(),
                MachineRepresentation::kFloat64, Type::Number());
     if (lower()) {
       ChangeToPureOp(node, Float64Op(node));
     }
@@ skipping 2080 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoProperties);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8