Reland "[turbofan] Weakening of types must weaken ranges inside unions."

This relands commit 4c1f4b79.

R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/723023002

Cr-Commit-Position: refs/heads/master@{#25317}

src/compiler/typer.cc

@@ -1119,10 +1119,9 @@ Bounds Typer::Visitor::TypeJSLoadNamed(Node* node) {
 // in the graph. In the current implementation, we are
 // increasing the limits to the closest power of two.
 Type* Typer::Visitor::Weaken(Type* current_type, Type* previous_type) {
-  if (current_type->IsRange() && previous_type->IsRange()) {
-    Type::RangeType* previous = previous_type->AsRange();
-    Type::RangeType* current = current_type->AsRange();
-
+  Type::RangeType* previous = previous_type->GetRange();
+  Type::RangeType* current = current_type->GetRange();
+  if (previous != NULL && current != NULL) {
     double current_min = current->Min()->Number();
     Handle<Object> new_min = current->Min();
 
@@ -1152,7 +1151,9 @@ Type* Typer::Visitor::Weaken(Type* current_type, Type* previous_type) {
       }
     }
 
-    return Type::Range(new_min, new_max, typer_->zone());
+    return Type::Union(current_type,
+                       Type::Range(new_min, new_max, typer_->zone()),
+                       typer_->zone());
   }
   return current_type;
 }

src/types.cc

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <iomanip>
+
 #include "src/types.h"
 
 #include "src/ostreams.h"
@@ -1017,8 +1019,12 @@ void TypeImpl<Config>::PrintTo(std::ostream& os, PrintDimension dim) {
     } else if (this->IsConstant()) {
       os << "Constant(" << Brief(*this->AsConstant()->Value()) << ")";
     } else if (this->IsRange()) {
+      std::ostream::fmtflags saved_flags = os.setf(std::ios::fixed);
+      std::streamsize saved_precision = os.precision(0);
       os << "Range(" << this->AsRange()->Min()->Number() << ", "
          << this->AsRange()->Max()->Number() << ")";
+      os.flags(saved_flags);
+      os.precision(saved_precision);
     } else if (this->IsContext()) {
       os << "Context(";
       this->AsContext()->Outer()->PrintTo(os, dim);

src/types.h

@@ -464,6 +464,11 @@ class TypeImpl : public Config::Base {
   double Min();
   double Max();
 
+  // Extracts a range from the type. If the type is a range, it just
+  // returns it; if it is a union, it returns the range component.
+  // Note that it does not contain range for constants.
+  RangeType* GetRange();
+
   int NumClasses();
   int NumConstants();
 
@@ -551,7 +556,6 @@ class TypeImpl : public Config::Base {
   static bool Contains(RangeType* lhs, RangeType* rhs);
   static bool Contains(RangeType* range, i::Object* val);
 
-  RangeType* GetRange();
   static int UpdateRange(
       RangeHandle type, UnionHandle result, int size, Region* region);
 

test/cctest/test-types.cc

@@ -1831,6 +1831,32 @@ struct Tests : Rep {
     */
   }
 
+  void GetRange() {
+    // GetRange(Range(a, b)) = Range(a, b).
+    for (TypeIterator it1 = T.types.begin(); it1 != T.types.end(); ++it1) {
+      TypeHandle type1 = *it1;
+      if (type1->IsRange()) {
+        typename Type::RangeType* range = type1->GetRange();
+        CHECK(type1->Min() == range->Min()->Number());
+        CHECK(type1->Max() == range->Max()->Number());
+      }
+    }
+
+    // GetRange(Union(Constant(x), Range(min,max))) == Range(min, max).
+    for (TypeIterator it1 = T.types.begin(); it1 != T.types.end(); ++it1) {
+      for (TypeIterator it2 = T.types.begin(); it2 != T.types.end(); ++it2) {
+        TypeHandle type1 = *it1;
+        TypeHandle type2 = *it2;
+        if (type1->IsConstant() && type2->IsRange()) {
+          TypeHandle u = T.Union(type1, type2);
+
+          CHECK(type2->Min() == u->GetRange()->Min()->Number());
+          CHECK(type2->Max() == u->GetRange()->Max()->Number());
+        }
+      }
+    }
+  }
+
   template<class Type2, class TypeHandle2, class Region2, class Rep2>
   void Convert() {
     Types<Type2, TypeHandle2, Region2> T2(
@@ -2030,6 +2056,13 @@ TEST(Distributivity) {
 }
 
 
+TEST(GetRange) {
+  CcTest::InitializeVM();
+  ZoneTests().GetRange();
+  HeapTests().GetRange();
+}
+
+
 TEST(Convert) {
   CcTest::InitializeVM();
   ZoneTests().Convert<HeapType, Handle<HeapType>, Isolate, HeapRep>();

test/mjsunit/regress/regress-weakening-multiplication.js

+// 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.
+
+function f() {
+  for (var j = 1; j < 1; j *= -8) {
+  }
+  for (var i = 1; i < 1; j += 2) {
+    j * -1;
+  }
+}
+f();