Revert of [builtins] Introduce proper Float64Exp operator.

src/crankshaft/hydrogen-instructions.cc

Index: src/crankshaft/hydrogen-instructions.cc
diff --git a/src/crankshaft/hydrogen-instructions.cc b/src/crankshaft/hydrogen-instructions.cc
index 5d3c56d5b6f7d2232dbce9e98d85e77a13055d6c..70b3f6d54164a316b31e167a35165c25a864cc09 100644
--- a/src/crankshaft/hydrogen-instructions.cc
+++ b/src/crankshaft/hydrogen-instructions.cc
@@ -3423,7 +3423,8 @@
     }
     switch (op) {
       case kMathExp:
-        return H_CONSTANT_DOUBLE(base::ieee754::exp(d));
+        lazily_initialize_fast_exp(isolate);
+        return H_CONSTANT_DOUBLE(fast_exp(d, isolate));
       case kMathLog:
         return H_CONSTANT_DOUBLE(base::ieee754::log(d));
       case kMathSqrt: