[turbofan] Generalize constant propagation.

src/compiler/js-typed-lowering.cc

Index: src/compiler/js-typed-lowering.cc
diff --git a/src/compiler/js-typed-lowering.cc b/src/compiler/js-typed-lowering.cc
index 2338866d6d2274830dff5b132128ca3f9216659b..5b9e3dbb98fa05335f8c7e88f590e7888e745de3 100644
--- a/src/compiler/js-typed-lowering.cc
+++ b/src/compiler/js-typed-lowering.cc
@@ -927,14 +927,21 @@ Reduction JSTypedLowering::ReduceJSStoreContext(Node* 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: