Revert of [builtins] Introduce proper Float64Exp operator.

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 84c07dc9d5926473ec657e84e3ebeba2be79dd66..363ad9db4e8ed946858ce5b89c70338c9b9bdf67 100644
--- a/src/compiler/js-builtin-reducer.cc
+++ b/src/compiler/js-builtin-reducer.cc
@@ -137,18 +137,6 @@
     // Math.clz32(a:plain-primitive) -> NumberClz32(ToUint32(a))
     Node* input = ToUint32(r.GetJSCallInput(0));
     Node* value = graph()->NewNode(simplified()->NumberClz32(), input);
-    return Replace(value);
-  }
-  return NoChange();
-}
-
-// ES6 section 20.2.2.14 Math.exp ( x )
-Reduction JSBuiltinReducer::ReduceMathExp(Node* node) {
-  JSCallReduction r(node);
-  if (r.InputsMatchOne(Type::PlainPrimitive())) {
-    // Math.exp(a:plain-primitive) -> NumberExp(ToNumber(a))
-    Node* input = ToNumber(r.GetJSCallInput(0));
-    Node* value = graph()->NewNode(simplified()->NumberExp(), input);
     return Replace(value);
   }
   return NoChange();
@@ -360,9 +348,6 @@
     case kMathCeil:
       reduction = ReduceMathCeil(node);
       break;
-    case kMathExp:
-      reduction = ReduceMathExp(node);
-      break;
     case kMathFloor:
       reduction = ReduceMathFloor(node);
       break;