[turbofan] Support for %_DoubleHi, %_DoubleLo and %_ConstructDouble.

src/base/bits.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/base/bits.h"
 
 #include <limits>
 
 #include "src/base/logging.h"
 
@@ skipping 30 matching lines @@
   if (rhs == -1) return -lhs;
   return lhs / rhs;
 }
 
 
 int32_t SignedMod32(int32_t lhs, int32_t rhs) {
   if (rhs == 0 || rhs == -1) return 0;
   return lhs % rhs;
 }
 
+
+uint64_t InsertElement64(uint64_t val, uint32_t elm, uint8_t off) {
+  switch (off) {
+    case 0:
+      val &= ~V8_UINT64_C(0xFFFFFFFF);
+      val |= static_cast<uint64_t>(elm) << 0;
+      return val;
+    case 1:
+      val &= V8_UINT64_C(0xFFFFFFFF);
+      val |= static_cast<uint64_t>(elm) << 32;
+      return val;
+    default:
+      UNREACHABLE();
+      return 0;
+  }
+}
+
 }  // namespace bits
 }  // namespace base
 }  // namespace v8