Take output type into account in JSTypedLowering reduction.

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 39104bb50d2f5093669d6d627e312a0970d2c0d5..e6610a72dd51d44febd34d70e5fccd5f8192f7fe 100644
--- a/src/compiler/js-typed-lowering.cc
+++ b/src/compiler/js-typed-lowering.cc
@@ -630,6 +630,15 @@ static Reduction ReplaceWithReduction(Node* node, Reduction reduction) {
 
 
 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.
+  if (node->bounds().upper->IsConstant() &&
+      !IrOpcode::IsLeafOpcode(node->opcode()) &&
+      !OperatorProperties::HasEffectOutput(node->op())) {
+    return ReplaceEagerly(node, jsgraph()->Constant(
+        node->bounds().upper->AsConstant()->Value()));
+    // TODO(neis): Extend this to Range(x,x), NaN, MinusZero, ...?
+  }
   switch (node->opcode()) {
     case IrOpcode::kJSEqual:
       return ReduceJSEqual(node, false);