[builtins] Add support for JS builtins written in TurboFan.

src/compiler/js-builtin-reducer.cc

Index: src/compiler/js-builtin-reducer.cc
diff --git a/src/compiler/js-builtin-reducer.cc b/src/compiler/js-builtin-reducer.cc
index 3023031c2f4f82f0a923652cd47198bae98fd512..aae8d8f374519685c4d42a492266b689d9e8a4fb 100644
--- a/src/compiler/js-builtin-reducer.cc
+++ b/src/compiler/js-builtin-reducer.cc
@@ -168,6 +168,17 @@ Reduction JSBuiltinReducer::ReduceMathRound(Node* node) {
   return NoChange();
 }
 
+// ES6 section 20.2.2.28 Math.sqrt ( x )

[Michael Starzinger, 2016/03/22 12:54:32]

nit: s/20.2.2.28/20.2.2.32/ ... or whatever other format we use these days to
reference sections in the spec. I list track. :)

[Benedikt Meurer, 2016/03/22 13:01:18]

Done.

+Reduction JSBuiltinReducer::ReduceMathSqrt(Node* node) {
+  JSCallReduction r(node);
+  if (r.InputsMatchOne(Type::Number())) {
+    // Math.sqrt(a:number) -> Float64Sqrt(a)
+    Node* value = graph()->NewNode(machine()->Float64Sqrt(), r.left());
+    return Replace(value);
+  }
+  return NoChange();
+}
+
 Reduction JSBuiltinReducer::Reduce(Node* node) {
   Reduction reduction = NoChange();
   JSCallReduction r(node);
@@ -187,6 +198,9 @@ Reduction JSBuiltinReducer::Reduce(Node* node) {
     case kMathRound:
       reduction = ReduceMathRound(node);
       break;
+    case kMathSqrt:
+      reduction = ReduceMathSqrt(node);
+      break;
     default:
       break;
   }