[turbofan] Generalize constant propagation.

src/compiler/js-typed-lowering.cc

 // 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.
 
 #include "src/compiler/access-builder.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/node-aux-data-inl.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 909 matching lines @@
   node->set_op(
       simplified()->StoreField(AccessBuilder::ForContextSlot(access.index())));
   node->RemoveInput(2);
   DCHECK_EQ(4, node->InputCount());
   return Changed(node);
 }
 
 
 Reduction JSTypedLowering::Reduce(Node* node) {
   // Check if the output type is a singleton.  In that case we already know the
-  // result value and can simply replace the node unless there are effects.
+  // result value and can simply replace the node if it's eliminatable.

[Jarin, 2015/01/05 09:41:21]

eliminatable -> eliminable?

[Benedikt Meurer, 2015/01/05 12:37:12]

Done.

   if (NodeProperties::IsTyped(node) &&
-      NodeProperties::GetBounds(node).upper->IsConstant() &&
       !IrOpcode::IsLeafOpcode(node->opcode()) &&
-      node->op()->EffectOutputCount() == 0) {
-    return ReplaceEagerly(node, jsgraph()->Constant(
-        NodeProperties::GetBounds(node).upper->AsConstant()->Value()));
-    // TODO(neis): Extend this to Range(x,x), NaN, MinusZero, ...?
+      node->op()->HasProperty(Operator::kEliminatable)) {
+    Type* upper = NodeProperties::GetBounds(node).upper;
+    if (upper->IsConstant()) {
+      Node* replacement = jsgraph()->Constant(upper->AsConstant()->Value());
+      NodeProperties::ReplaceWithValue(node, replacement);
+      return Changed(replacement);
+    } else if (upper->Is(Type::Number()) &&
+               base::bit_equal_to<double>()(upper->Min(), upper->Max())) {
+      Node* replacement = jsgraph()->Constant(upper->Min());
+      NodeProperties::ReplaceWithValue(node, replacement);
+      return Changed(replacement);
+    }
   }
   switch (node->opcode()) {
     case IrOpcode::kJSEqual:
       return ReduceJSEqual(node, false);
     case IrOpcode::kJSNotEqual:
       return ReduceJSEqual(node, true);
     case IrOpcode::kJSStrictEqual:
       return ReduceJSStrictEqual(node, false);
     case IrOpcode::kJSStrictNotEqual:
       return ReduceJSStrictEqual(node, true);
@@ skipping 128 matching lines @@
 }
 
 
 MachineOperatorBuilder* JSTypedLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8