[turbofan] Do constant folding for Float64Pow.

src/utils.h

 // Copyright 2012 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.
 
 #ifndef V8_UTILS_H_
 #define V8_UTILS_H_
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 216 matching lines @@
 
 // Floor(-0.0) == 0.0
 inline double Floor(double x) {
 #if V8_CC_MSVC
   if (x == 0) return x;  // Fix for issue 3477.
 #endif
   return std::floor(x);
 }
 
 inline double Pow(double x, double y) {
+  if (std::isnan(y) || ((x == 1 || x == -1) && std::isinf(y))) {
+    return std::numeric_limits<double>::quiet_NaN();
+  }
 #if (defined(__MINGW64_VERSION_MAJOR) &&                              \
      (!defined(__MINGW64_VERSION_RC) || __MINGW64_VERSION_RC < 1)) || \
     defined(V8_OS_AIX)
   // MinGW64 and AIX have a custom implementation for pow.  This handles certain
   // special cases that are different.
   if ((x == 0.0 || std::isinf(x)) && y != 0.0 && std::isfinite(y)) {
     double f;
     double result = ((x == 0.0) ^ (y > 0)) ? V8_INFINITY : 0;
     /* retain sign if odd integer exponent */
     return ((std::modf(y, &f) == 0.0) && (static_cast<int64_t>(y) & 1))
@@ skipping 1340 matching lines @@
   byte* dst = reinterpret_cast<byte*>(p);
   for (size_t i = 0; i < sizeof(V); i++) {
     dst[i] = src[sizeof(V) - i - 1];
   }
 #endif  // V8_TARGET_LITTLE_ENDIAN
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_UTILS_H_