Refine typing of addition, subtraction, multiplication, and division.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index b6604c7f384b323cb3306adf70a07402485d0d16..56c6b8bc93785446a0884ef232064765e02f1245 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -32,8 +32,8 @@ Typer::Typer(Graph* graph, MaybeHandle<Context> context)
 
   Handle<Object> zero = f->NewNumber(0);
   Handle<Object> one = f->NewNumber(1);
-  Handle<Object> positive_infinity = f->NewNumber(+V8_INFINITY);
-  Handle<Object> negative_infinity = f->NewNumber(-V8_INFINITY);
+  Handle<Object> infinity = f->NewNumber(+V8_INFINITY);
+  Handle<Object> minusinfinity = f->NewNumber(-V8_INFINITY);
 
   negative_signed32 = Type::Union(
       Type::SignedSmall(), Type::OtherSigned32(), zone);
@@ -49,7 +49,9 @@ Typer::Typer(Graph* graph, MaybeHandle<Context> context)
       singleton_zero, Type::Union(Type::NaN(), Type::MinusZero(), zone), zone);
   falsish = Type::Union(Type::Undetectable(),
       Type::Union(zeroish, undefined_or_null, zone), zone);
-  integer = Type::Range(negative_infinity, positive_infinity, zone);
+  integer = Type::Range(minusinfinity, infinity, zone);
+  weakint = Type::Union(
+      integer, Type::Union(Type::NaN(), Type::MinusZero(), zone), zone);
 
   Type* number = Type::Number();
   Type* signed32 = Type::Signed32();
@@ -57,8 +59,6 @@ Typer::Typer(Graph* graph, MaybeHandle<Context> context)
   Type* integral32 = Type::Integral32();
   Type* object = Type::Object();
   Type* undefined = Type::Undefined();
-  Type* weakint = Type::Union(
-      integer, Type::Union(Type::NaN(), Type::MinusZero(), zone), zone);
 
   number_fun0_ = Type::Function(number, zone);
   number_fun1_ = Type::Function(number, number, zone);
@@ -164,7 +164,7 @@ class Typer::Visitor : public NullNodeVisitor {
 
   Bounds BoundsOrNone(Node* node) {
     return NodeProperties::IsTyped(node)
-        ? NodeProperties::GetBounds(node) : Bounds(Type::None(zone()));
+        ? NodeProperties::GetBounds(node) : Bounds(Type::None());
   }
 
   Bounds Operand(Node* node, int i) {
@@ -197,6 +197,7 @@ class Typer::Visitor : public NullNodeVisitor {
 
   static Type* Invert(Type*, Typer*);
   static Type* FalsifyUndefined(Type*, Typer*);
+  static Type* Rangify(Type*, Typer*);
 
   static Type* ToPrimitive(Type*, Typer*);
   static Type* ToBoolean(Type*, Typer*);
@@ -250,11 +251,11 @@ class Typer::NarrowVisitor : public Typer::Visitor {
   GenericGraphVisit::Control Pre(Node* node) {
     if (OperatorProperties::HasValueOutput(node->op())) {
       Bounds previous = NodeProperties::GetBounds(node);
-      Bounds bounds = TypeNode(node);
-      NodeProperties::SetBounds(node, Bounds::Both(bounds, previous, zone()));
-      DCHECK(bounds.Narrows(previous));
+      Bounds current = TypeNode(node);
+      NodeProperties::SetBounds(node, Bounds::Both(current, previous, zone()));
+      DCHECK(current.Narrows(previous));
       // Stop when nothing changed (but allow re-entry in case it does later).
-      return previous.Narrows(bounds)
+      return previous.Narrows(current)
           ? GenericGraphVisit::DEFER : GenericGraphVisit::REENTER;
     } else {
       return GenericGraphVisit::SKIP;
@@ -274,12 +275,17 @@ class Typer::WidenVisitor : public Typer::Visitor {
   GenericGraphVisit::Control Pre(Node* node) {
     if (OperatorProperties::HasValueOutput(node->op())) {
       Bounds previous = BoundsOrNone(node);
-      Bounds bounds = TypeNode(node);
-      DCHECK(previous.lower->Is(bounds.lower));
-      DCHECK(previous.upper->Is(bounds.upper));
-      NodeProperties::SetBounds(node, bounds);
+      Bounds current = TypeNode(node);
+      DCHECK(previous.lower->Is(current.lower));
+      DCHECK(previous.upper->Is(current.upper));
+
+      // Speed up termination in the presence of range types:
+      current.upper = MaybeWeaken(current.upper, previous.upper);
+      current.lower = MaybeWeaken(current.lower, previous.lower);
+
+      NodeProperties::SetBounds(node, current);
       // Stop when nothing changed (but allow re-entry in case it does later).
-      return bounds.Narrows(previous)
+      return previous.Narrows(current) && current.Narrows(previous)
           ? GenericGraphVisit::DEFER : GenericGraphVisit::REENTER;
     } else {
       return GenericGraphVisit::SKIP;
@@ -289,6 +295,14 @@ class Typer::WidenVisitor : public Typer::Visitor {
   GenericGraphVisit::Control Post(Node* node) {
     return GenericGraphVisit::REENTER;
   }
+
+ private:
+  Type* MaybeWeaken(Type* current, Type* previous) {
+    if (current->IsRange() && previous->IsRange() && !current->Is(previous)) {
+      return current->AsRange()->Weaken(zone());
+    }
+    return current;
+  }
 };
 
 
@@ -379,6 +393,15 @@ Type* Typer::Visitor::FalsifyUndefined(Type* type, Typer* t) {
 }
 
 
+Type* Typer::Visitor::Rangify(Type* type, Typer* t) {
+  if (!type->Is(t->integer)) return type;  // Give up.
+  if (type->IsRange()) return type;  // Shortcut.
+  Factory* f = t->isolate()->factory();
+  return Type::Range(
+      f->NewNumber(type->Min()), f->NewNumber(type->Max()), t->zone());
+}
+
+
 // Type conversion.
 
 
@@ -453,7 +476,7 @@ Bounds Typer::Visitor::TypeParameter(Node* node) {
 
 
 Bounds Typer::Visitor::TypeInt32Constant(Node* node) {
-  Factory* f = zone()->isolate()->factory();
+  Factory* f = isolate()->factory();
   Handle<Object> number = f->NewNumber(OpParameter<int32_t>(node));
   return Bounds(Type::Intersect(
       Type::Range(number, number, zone()), Type::UntaggedInt32(), zone()));
@@ -480,7 +503,7 @@ Bounds Typer::Visitor::TypeFloat64Constant(Node* node) {
 
 
 Bounds Typer::Visitor::TypeNumberConstant(Node* node) {
-  Factory* f = zone()->isolate()->factory();
+  Factory* f = isolate()->factory();
   return Bounds(Type::Constant(
       f->NewNumber(OpParameter<double>(node)), zone()));
 }
@@ -657,7 +680,7 @@ Type* Typer::Visitor::JSGreaterThanOrEqualTyper(
 
 
 Type* Typer::Visitor::JSBitwiseOrTyper(Type* lhs, Type* rhs, Typer* t) {
-  Factory* f = t->zone()->isolate()->factory();
+  Factory* f = t->isolate()->factory();
   lhs = NumberToInt32(ToNumber(lhs, t), t);
   rhs = NumberToInt32(ToNumber(rhs, t), t);
   double lmin = lhs->Min();
@@ -681,7 +704,7 @@ Type* Typer::Visitor::JSBitwiseOrTyper(Type* lhs, Type* rhs, Typer* t) {
 
 
 Type* Typer::Visitor::JSBitwiseAndTyper(Type* lhs, Type* rhs, Typer* t) {
-  Factory* f = t->zone()->isolate()->factory();
+  Factory* f = t->isolate()->factory();
   lhs = NumberToInt32(ToNumber(lhs, t), t);
   rhs = NumberToInt32(ToNumber(rhs, t), t);
   double lmin = lhs->Min();
@@ -729,7 +752,7 @@ Type* Typer::Visitor::JSShiftLeftTyper(Type* lhs, Type* rhs, Typer* t) {
 
 Type* Typer::Visitor::JSShiftRightTyper(Type* lhs, Type* rhs, Typer* t) {
   lhs = NumberToInt32(ToNumber(lhs, t), t);
-  Factory* f = t->zone()->isolate()->factory();
+  Factory* f = t->isolate()->factory();
   if (lhs->Min() >= 0) {
     // Right-shifting a non-negative value cannot make it negative, nor larger.
     Handle<Object> min = f->NewNumber(0);
@@ -748,7 +771,7 @@ Type* Typer::Visitor::JSShiftRightTyper(Type* lhs, Type* rhs, Typer* t) {
 
 Type* Typer::Visitor::JSShiftRightLogicalTyper(Type* lhs, Type* rhs, Typer* t) {
   lhs = NumberToUint32(ToNumber(lhs, t), t);
-  Factory* f = t->zone()->isolate()->factory();
+  Factory* f = t->isolate()->factory();
   // Logical right-shifting any value cannot make it larger.
   Handle<Object> min = f->NewNumber(0);
   Handle<Object> max = f->NewNumber(lhs->Max());
@@ -759,6 +782,63 @@ Type* Typer::Visitor::JSShiftRightLogicalTyper(Type* lhs, Type* rhs, Typer* t) {
 // JS arithmetic operators.
 
 
+// Returns the array's least element, ignoring NaN.
+// There must be at least one non-NaN element.
+// Any -0 is converted to 0.
+static double array_min(double a[], size_t n) {
+  DCHECK(n != 0);
+  double x = a[0];
+  for (size_t i = 1; i < n; ++i) {
+    x = std::min(std::isnan(a[i]) ? +V8_INFINITY : a[i], x);
+  }
+  DCHECK(!std::isnan(x));
+  return x == 0 ? 0 : x;  // -0 -> 0
+}
+
+
+// Returns the array's greatest element, ignoring NaN.
+// There must be at least one non-NaN element.
+// Any -0 is converted to 0.
+static double array_max(double a[], size_t n) {
+  DCHECK(n != 0);
+  double x = a[0];
+  for (size_t i = 1; i < n; ++i) {
+    x = std::max(std::isnan(a[i]) ? -V8_INFINITY : a[i], x);
+  }
+  DCHECK(!std::isnan(x));
+  return x == 0 ? 0 : x;  // -0 -> 0
+}
+
+
+Type* Typer::Visitor::JSAddRanger(
+    Type::RangeType* lhs, Type::RangeType* rhs, Typer* t) {
+  double results[4];
+  results[0] = lhs->Min()->Number() + rhs->Min()->Number();
+  results[1] = lhs->Min()->Number() + rhs->Max()->Number();
+  results[2] = lhs->Max()->Number() + rhs->Min()->Number();
+  results[3] = lhs->Max()->Number() + rhs->Max()->Number();
+  // Since none of the inputs can be -0, the result cannot be -0 either.
+  // However, it can be nan (the sum of two infinities of opposite sign).
+  // On the other hand, if none of the "results" above is nan, then the actual
+  // result cannot be nan either.
+  int nans = 0;
+  for (int i = 0; i < 4; ++i) {
+    if (std::isnan(results[i])) ++nans;
+  }
+  if (nans == 4) return Type::NaN();  // [-inf..-inf] + [inf..inf] or vice versa
+  Factory* f = t->isolate()->factory();
+  Type* range = Type::Range(
+      f->NewNumber(array_min(results, 4)), f->NewNumber(array_max(results, 4)),
+      t->zone());
+  return nans == 0 ? range : Type::Union(range, Type::NaN(), t->zone());
+  // Examples:
+  //   [-inf, -inf] + [+inf, +inf] = NaN
+  //   [-inf, -inf] + [n, +inf] = [-inf, -inf] \/ NaN
+  //   [-inf, +inf] + [n, +inf] = [-inf, +inf] \/ NaN
+  //   [-inf, m] + [n, +inf] = [-inf, +inf] \/ NaN
+}
+
+
 Type* Typer::Visitor::JSAddTyper(Type* lhs, Type* rhs, Typer* t) {
   lhs = ToPrimitive(lhs, t);
   rhs = ToPrimitive(rhs, t);
@@ -769,29 +849,97 @@ Type* Typer::Visitor::JSAddTyper(Type* lhs, Type* rhs, Typer* t) {
       return Type::NumberOrString();
     }
   }
-  lhs = ToNumber(lhs, t);
-  rhs = ToNumber(rhs, t);
+  lhs = Rangify(ToNumber(lhs, t), t);
+  rhs = Rangify(ToNumber(rhs, t), t);
   if (lhs->Is(Type::NaN()) || rhs->Is(Type::NaN())) return Type::NaN();
-  // TODO(neis): Do some analysis.
+  if (lhs->IsRange() && rhs->IsRange()) {
+    return JSAddRanger(lhs->AsRange(), rhs->AsRange(), t);
+  }
   // TODO(neis): Deal with numeric bitsets here and elsewhere.
   return Type::Number();
 }
 
 
+Type* Typer::Visitor::JSSubtractRanger(
+    Type::RangeType* lhs, Type::RangeType* rhs, Typer* t) {
+  double results[4];
+  results[0] = lhs->Min()->Number() - rhs->Min()->Number();
+  results[1] = lhs->Min()->Number() - rhs->Max()->Number();
+  results[2] = lhs->Max()->Number() - rhs->Min()->Number();
+  results[3] = lhs->Max()->Number() - rhs->Max()->Number();
+  // Since none of the inputs can be -0, the result cannot be -0.
+  // However, it can be nan (the subtraction of two infinities of same sign).
+  // On the other hand, if none of the "results" above is nan, then the actual
+  // result cannot be nan either.
+  int nans = 0;
+  for (int i = 0; i < 4; ++i) {
+    if (std::isnan(results[i])) ++nans;
+  }
+  if (nans == 4) return Type::NaN();  // [inf..inf] - [inf..inf] (all same sign)
+  Factory* f = t->isolate()->factory();
+  Type* range = Type::Range(
+      f->NewNumber(array_min(results, 4)), f->NewNumber(array_max(results, 4)),
+      t->zone());
+  return nans == 0 ? range : Type::Union(range, Type::NaN(), t->zone());
+  // Examples:
+  //   [-inf, +inf] - [-inf, +inf] = [-inf, +inf] \/ NaN
+  //   [-inf, -inf] - [-inf, -inf] = NaN
+  //   [-inf, -inf] - [n, +inf] = [-inf, -inf] \/ NaN
+  //   [m, +inf] - [-inf, n] = [-inf, +inf] \/ NaN
+}
+
+
 Type* Typer::Visitor::JSSubtractTyper(Type* lhs, Type* rhs, Typer* t) {
-  lhs = ToNumber(lhs, t);
-  rhs = ToNumber(rhs, t);
+  lhs = Rangify(ToNumber(lhs, t), t);
+  rhs = Rangify(ToNumber(rhs, t), t);
   if (lhs->Is(Type::NaN()) || rhs->Is(Type::NaN())) return Type::NaN();
-  // TODO(neis): Do some analysis.
+  if (lhs->IsRange() && rhs->IsRange()) {
+    return JSSubtractRanger(lhs->AsRange(), rhs->AsRange(), t);
+  }
   return Type::Number();
 }
 
 
+Type* Typer::Visitor::JSMultiplyRanger(
+    Type::RangeType* lhs, Type::RangeType* rhs, Typer* t) {
+  double results[4];
+  double lmin = lhs->Min()->Number();
+  double lmax = lhs->Max()->Number();
+  double rmin = rhs->Min()->Number();
+  double rmax = rhs->Max()->Number();
+  results[0] = lmin * rmin;
+  results[1] = lmin * rmax;
+  results[2] = lmax * rmin;
+  results[3] = lmax * rmax;
+  // If the result may be nan, we give up on calculating a precise type, because
+  // the discontinuity makes it too complicated.  Note that even if none of the
+  // "results" above is nan, the actual result may still be, so we have to do a
+  // different check:
+  bool maybe_nan =
+      (lhs->Maybe(t->singleton_zero) &&
+          (rmin == -V8_INFINITY || rmax == +V8_INFINITY)) ||
+      (rhs->Maybe(t->singleton_zero) &&
+          (lmin == -V8_INFINITY || lmax == +V8_INFINITY));
+  if (maybe_nan) return t->weakint;  // Giving up.
+  bool maybe_minuszero =
+    (lhs->Maybe(t->singleton_zero) && rmin < 0) ||
+    (rhs->Maybe(t->singleton_zero) && lmin < 0);
+  Factory* f = t->isolate()->factory();
+  Type* range = Type::Range(
+      f->NewNumber(array_min(results, 4)), f->NewNumber(array_max(results, 4)),
+      t->zone());
+  return maybe_minuszero ?
+      Type::Union(range, Type::MinusZero(), t->zone()) : range;
+}
+
+
 Type* Typer::Visitor::JSMultiplyTyper(Type* lhs, Type* rhs, Typer* t) {
-  lhs = ToNumber(lhs, t);
-  rhs = ToNumber(rhs, t);
+  lhs = Rangify(ToNumber(lhs, t), t);
+  rhs = Rangify(ToNumber(rhs, t), t);
   if (lhs->Is(Type::NaN()) || rhs->Is(Type::NaN())) return Type::NaN();
-  // TODO(neis): Do some analysis.
+  if (lhs->IsRange() && rhs->IsRange()) {
+    return JSMultiplyRanger(lhs->AsRange(), rhs->AsRange(), t);
+  }
   return Type::Number();
 }
 
@@ -800,8 +948,14 @@ Type* Typer::Visitor::JSDivideTyper(Type* lhs, Type* rhs, Typer* t) {
   lhs = ToNumber(lhs, t);
   rhs = ToNumber(rhs, t);
   if (lhs->Is(Type::NaN()) || rhs->Is(Type::NaN())) return Type::NaN();
-  // TODO(neis): Do some analysis.
-  return Type::Number();
+  // Division is tricky, so all we do is try ruling out nan.
+  // TODO(neis): try ruling out -0 as well?
+  bool maybe_nan =
+      lhs->Maybe(Type::NaN()) || rhs->Maybe(Type::NaN()) ||
+      rhs->Maybe(t->singleton_zero) ||
+      ((lhs->Min() == -V8_INFINITY || lhs->Max() == +V8_INFINITY) &&
+       (rhs->Min() == -V8_INFINITY || rhs->Max() == +V8_INFINITY));
+  return maybe_nan ? Type::Number() : Type::OrderedNumber();
 }