[turbofan] Improve typing rules for NumberFloor and NumberDivide.

Also rule out -0 for NumberDivide if possible, and rule out NaN and -0
for NumberFloor if possible.

R=jarin@chromium.org
BUG=v8:5267

Review-Url: https://codereview.chromium.org/2609373002
Cr-Commit-Position: refs/heads/master@{#42059}

src/compiler/operation-typer.cc

@@ -366,8 +366,9 @@ Type* OperationTyper::NumberExpm1(Type* type) {
 Type* OperationTyper::NumberFloor(Type* type) {
   DCHECK(type->Is(Type::Number()));
   if (type->Is(cache_.kIntegerOrMinusZeroOrNaN)) return type;
-  // TODO(bmeurer): We could infer a more precise type here.
-  return cache_.kIntegerOrMinusZeroOrNaN;
+  type = Type::Intersect(type, Type::MinusZeroOrNaN(), zone());
+  type = Type::Union(type, cache_.kInteger, zone());
+  return type;
 }
 
 Type* OperationTyper::NumberFround(Type* type) {
@@ -624,12 +625,19 @@ Type* OperationTyper::NumberDivide(Type* lhs, Type* rhs) {
   }
 
   if (lhs->Is(Type::NaN()) || rhs->Is(Type::NaN())) return Type::NaN();
-  // Division is tricky, so all we do is try ruling out nan.
+  // Division is tricky, so all we do is try ruling out -0 and NaN.
+  bool maybe_minuszero = !lhs->Is(cache_.kPositiveIntegerOrNaN) ||
+                         !rhs->Is(cache_.kPositiveIntegerOrNaN);
   bool maybe_nan =
       lhs->Maybe(Type::NaN()) || rhs->Maybe(cache_.kZeroish) ||
       ((lhs->Min() == -V8_INFINITY || lhs->Max() == +V8_INFINITY) &&
        (rhs->Min() == -V8_INFINITY || rhs->Max() == +V8_INFINITY));
-  return maybe_nan ? Type::Number() : Type::OrderedNumber();
+
+  // Take into account the -0 and NaN information computed earlier.
+  Type* type = Type::PlainNumber();
+  if (maybe_minuszero) type = Type::Union(type, Type::MinusZero(), zone());
+  if (maybe_nan) type = Type::Union(type, Type::NaN(), zone());
+  return type;
 }
 
 Type* OperationTyper::NumberModulus(Type* lhs, Type* rhs) {

src/compiler/type-cache.h

@@ -64,6 +64,8 @@ class TypeCache final {
   Type* const kPositiveInteger = CreateRange(0.0, V8_INFINITY);
   Type* const kPositiveIntegerOrMinusZero =
       Type::Union(kPositiveInteger, Type::MinusZero(), zone());
+  Type* const kPositiveIntegerOrNaN =
+      Type::Union(kPositiveInteger, Type::NaN(), zone());
   Type* const kPositiveIntegerOrMinusZeroOrNaN =
       Type::Union(kPositiveIntegerOrMinusZero, Type::NaN(), zone());