[builtins] Migrate Math.log to TurboFan.

src/compiler/js-builtin-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/objects-inl.h"
@@ skipping 165 matching lines @@
   JSCallReduction r(node);
   if (r.InputsMatchOne(Type::NumberOrUndefined())) {
     // Math.fround(a:number) -> TruncateFloat64ToFloat32(a)
     Node* value =
         graph()->NewNode(machine()->TruncateFloat64ToFloat32(), r.left());
     return Replace(value);
   }
   return NoChange();
 }
 
+// ES6 section 20.2.2.20 Math.log ( x )
+Reduction JSBuiltinReducer::ReduceMathLog(Node* node) {
+  JSCallReduction r(node);
+  if (r.InputsMatchOne(Type::Number())) {
+    // Math.log(a:number) -> NumberLog(a)
+    Node* value = graph()->NewNode(simplified()->NumberLog(), r.left());
+    return Replace(value);
+  }
+  return NoChange();
+}
+
 // ES6 section 20.2.2.28 Math.round ( x )
 Reduction JSBuiltinReducer::ReduceMathRound(Node* node) {
   JSCallReduction r(node);
   if (r.InputsMatchOne(Type::Number())) {
     // Math.round(a:number) -> NumberRound(a)
     Node* value = graph()->NewNode(simplified()->NumberRound(), r.left());
     return Replace(value);
   }
   return NoChange();
 }
@@ skipping 50 matching lines @@
       break;
     case kMathCeil:
       reduction = ReduceMathCeil(node);
       break;
     case kMathFloor:
       reduction = ReduceMathFloor(node);
       break;
     case kMathFround:
       reduction = ReduceMathFround(node);
       break;
+    case kMathLog:
+      reduction = ReduceMathLog(node);
+      break;
     case kMathRound:
       reduction = ReduceMathRound(node);
       break;
     case kMathSqrt:
       reduction = ReduceMathSqrt(node);
       break;
     case kMathTrunc:
       reduction = ReduceMathTrunc(node);
       break;
     case kStringFromCharCode:
@@ skipping 27 matching lines @@
 }
 
 
 SimplifiedOperatorBuilder* JSBuiltinReducer::simplified() const {
   return jsgraph()->simplified();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8