[builtins] Introduce proper Float64Exp operator.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 3181477700b9ef53ecbe4b9f14466ae07265d2de..905427606bc7864e6fc2328dcf176066826c012a 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -2452,6 +2452,18 @@ void Builtins::Generate_MathClz32(CodeStubAssembler* assembler) {
   }
 }
 
+// ES6 section 20.2.2.14 Math.exp ( x )
+void Builtins::Generate_MathExp(CodeStubAssembler* assembler) {
+  using compiler::Node;
+
+  Node* x = assembler->Parameter(1);
+  Node* context = assembler->Parameter(4);
+  Node* x_value = assembler->TruncateTaggedToFloat64(context, x);
+  Node* value = assembler->Float64Exp(x_value);
+  Node* result = assembler->ChangeFloat64ToTagged(value);
+  assembler->Return(result);
+}
+
 // ES6 section 20.2.2.16 Math.floor ( x )
 void Builtins::Generate_MathFloor(CodeStubAssembler* assembler) {
   Generate_MathRoundingOperation(assembler, &CodeStubAssembler::Float64Floor);