[turbofan] Refine typing of equality

Generalize the HeapConstant case to a Singleton case.

Change-Id: Ief8c325a4326e02c8c361f3b41fc40ca398167ad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2096619
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66659}

src/compiler/operation-typer.cc

@@ -1245,9 +1245,11 @@ Type OperationTyper::StrictEqual(Type lhs, Type rhs) {
   if ((lhs.Is(Type::Hole()) || rhs.Is(Type::Hole())) && !lhs.Maybe(rhs)) {
     return singleton_false();
   }
-  if (lhs.IsHeapConstant() && rhs.Is(lhs)) {
+  if (lhs.IsSingleton() && rhs.Is(lhs)) {
     // Types are equal and are inhabited only by a single semantic value,
     // which is not nan due to the earlier check.
+    DCHECK(lhs.Is(rhs));
+    DCHECK(lhs.Is(Type::NonInternal()) || lhs.Is(Type::Hole()));
     return singleton_true();
   }
   return Type::Boolean();

src/compiler/typer.cc

@@ -1077,9 +1077,11 @@ Type Typer::Visitor::JSEqualTyper(Type lhs, Type rhs, Typer* t) {
       (lhs.Max() < rhs.Min() || lhs.Min() > rhs.Max())) {
     return t->singleton_false_;
   }
-  if (lhs.IsHeapConstant() && rhs.Is(lhs)) {
+  if (lhs.IsSingleton() && rhs.Is(lhs)) {
     // Types are equal and are inhabited only by a single semantic value,
     // which is not nan due to the earlier check.
+    DCHECK(lhs.Is(rhs));
+    DCHECK(lhs.Is(Type::NonInternal()) || lhs.Is(Type::Hole()));
     return t->singleton_true_;
   }
   return Type::Boolean();

src/compiler/types.cc

@@ -564,7 +564,7 @@ bool Type::SlowIs(Type that) const {
   }
 
   if (that.IsRange()) {
-    return (this->IsRange() && Contains(that.AsRange(), this->AsRange()));
+    return this->IsRange() && Contains(that.AsRange(), this->AsRange());
   }
   if (this->IsRange()) return false;
 

src/compiler/types.h

@@ -412,6 +412,13 @@ class V8_EXPORT_PRIVATE Type {
   }
   bool IsTuple() const { return IsKind(TypeBase::kTuple); }
 
+  bool IsSingleton() const {
+    if (IsNone()) return false;
+    return Is(Type::Null()) || Is(Type::Undefined()) || Is(Type::MinusZero()) ||
+           Is(Type::NaN()) || Is(Type::Hole()) || IsHeapConstant() ||
+           (Is(Type::PlainNumber()) && Min() == Max());
+  }
+
   const HeapConstantType* AsHeapConstant() const;
   const OtherNumberConstantType* AsOtherNumberConstant() const;
   const RangeType* AsRange() const;