[turbofan] More efficient truncation analysis for add, sub.

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 1086 matching lines @@
     Node* overflow = graph()->NewNode(common()->Projection(1), arith);
     effect =
         graph()->NewNode(simplified()->CheckIf(), overflow, effect, control);
     Node* value = graph()->NewNode(common()->Projection(0), arith);
     ReplaceEffectControlUses(node, effect, control);
     DeferReplacement(node, value);
   }
 
   void VisitSpeculativeAdditiveOp(Node* node, Truncation truncation,
                                   SimplifiedLowering* lowering) {
-    if (BothInputsAre(node, Type::Signed32()) &&
+    if (BothInputsAre(node, type_cache_.kSigned32OrMinusZero) &&
         NodeProperties::GetType(node)->Is(Type::Signed32())) {
       // int32 + int32 = int32   ==>   signed Int32Add/Sub
       VisitInt32Binop(node);
       if (lower()) ChangeToPureOp(node, Int32Op(node));
       return;
     }
 
     // Use truncation if available.
     if (BothInputsAre(node, type_cache_.kAdditiveSafeIntegerOrMinusZero) &&
         truncation.TruncatesToWord32()) {
       // safe-int + safe-int = x (truncated to int32)
       // => signed Int32Add/Sub (truncated)
       VisitWord32TruncatingBinop(node);
       if (lower()) ChangeToPureOp(node, Int32Op(node));
       return;
     }
 
     // Try to use type feedback.
     BinaryOperationHints::Hint hint = BinaryOperationHintOf(node->op());
 
-    // TODO(jarin) This might not be necessary (covered by the next case).
-    // The only real difference is that this one actually treats the
-    // inputs as truncated to word32.
-    if (BothInputsAre(node, Type::Signed32())) {
+    // Handle the case when no int32 checks on inputs are necessary
+    // (but an overflow check is needed on the output).
+    if (BothInputsAre(node, Type::Signed32()) ||
+        (BothInputsAre(node, type_cache_.kSigned32OrMinusZero) &&
+         NodeProperties::GetType(node)->Is(type_cache_.kSafeInteger))) {
       // If both the inputs the feedback are int32, use the overflow op.
       if (hint == BinaryOperationHints::kSignedSmall ||
           hint == BinaryOperationHints::kSigned32) {
         VisitBinop(node, UseInfo::TruncatingWord32(),
                    MachineRepresentation::kWord32, TypeCheckKind::kSigned32);
         if (lower()) {
           ChangeToInt32OverflowOp(node, Int32OverflowOp(node));
         }
         return;
       }
@@ skipping 1891 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