[turbofan] Improve NumberAbs lowering for Signed32 input.

We can just do the Int32Abs lowering always for Signed32 inputs.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2134143002
Cr-Commit-Position: refs/heads/master@{#37638}

src/compiler/simplified-lowering.cc

@@ -1601,7 +1601,7 @@ class RepresentationSelector {
           VisitUnop(node, UseInfo::TruncatingWord32(),
                     MachineRepresentation::kWord32);
           if (lower()) DeferReplacement(node, node->InputAt(0));
-        } else if (InputIs(node, type_cache_.kSafeSigned32)) {
+        } else if (InputIs(node, Type::Signed32())) {
           VisitUnop(node, UseInfo::TruncatingWord32(),
                     MachineRepresentation::kWord32);
           if (lower()) DeferReplacement(node, lowering->Int32Abs(node));

src/type-cache.h

@@ -73,7 +73,6 @@ class TypeCache final {
   Type* const kSafeIntegerOrMinusZero =
       Type::Union(kSafeInteger, Type::MinusZero(), zone());
   Type* const kPositiveSafeInteger = CreateRange(0.0, kMaxSafeInteger);
-  Type* const kSafeSigned32 = CreateRange(-kMaxInt, kMaxInt);
 
   Type* const kUntaggedUndefined =
       Type::Intersect(Type::Undefined(), Type::Untagged(), zone());