[turbofan] Unify Math.floor / Math.ceil optimization.

src/compiler/js-intrinsic-lowering.cc

Index: src/compiler/js-intrinsic-lowering.cc
diff --git a/src/compiler/js-intrinsic-lowering.cc b/src/compiler/js-intrinsic-lowering.cc
index 171b36e8d2300cac891fddaa7bbedf8b88cc62bf..317421f4ee2c0a93ffe48be7c0b34b6802e224c4 100644
--- a/src/compiler/js-intrinsic-lowering.cc
+++ b/src/compiler/js-intrinsic-lowering.cc
@@ -40,6 +40,8 @@ Reduction JSIntrinsicLowering::Reduce(Node* node) {
       return ReduceInlineDoubleHi(node);
     case Runtime::kInlineIsRegExp:
       return ReduceInlineIsInstanceType(node, JS_REGEXP_TYPE);
+    case Runtime::kInlineMathFloor:
+      return ReduceInlineMathFloor(node);
     case Runtime::kInlineValueOf:
       return ReduceInlineValueOf(node);
     default:
@@ -162,6 +164,12 @@ Reduction JSIntrinsicLowering::ReduceInlineIsInstanceType(
 }
 
 
+Reduction JSIntrinsicLowering::ReduceInlineMathFloor(Node* node) {
+  if (!machine()->HasFloat64RoundDown()) return NoChange();
+  return Change(node, machine()->Float64RoundDown());
+}
+
+
 Reduction JSIntrinsicLowering::ReduceInlineValueOf(Node* node) {
   // if (%_IsSmi(value)) {
   //   return value;