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

src/base/bits.cc

Index: src/base/bits.cc
diff --git a/src/base/bits.cc b/src/base/bits.cc
index 74d747fc9059f135cc2986b9b73f6ce473391534..09e6d29e363c23bdbe3414b8ab0fc99d07a573cf 100644
--- a/src/base/bits.cc
+++ b/src/base/bits.cc
@@ -48,6 +48,23 @@ int32_t SignedMod32(int32_t lhs, int32_t rhs) {
   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