Introduce intrinsics for double values in Javascript.

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7662 matching lines @@
   return isolate->heap()->AllocateHeapNumber(std::NAME(x));                    \
 }
 
 RUNTIME_UNARY_MATH(acos)
 RUNTIME_UNARY_MATH(asin)
 RUNTIME_UNARY_MATH(atan)
 RUNTIME_UNARY_MATH(log)
 #undef RUNTIME_UNARY_MATH
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_DoubleHi) {
+  SealHandleScope shs(isolate);
+  ASSERT(args.length() == 1);
+  CONVERT_DOUBLE_ARG_CHECKED(x, 0);
+  return isolate->heap()->NumberFromDouble(
+      static_cast<int32_t>(double_to_uint64(x) >> 32));
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_DoubleLo) {
+  SealHandleScope shs(isolate);
+  ASSERT(args.length() == 1);
+  CONVERT_DOUBLE_ARG_CHECKED(x, 0);
+  return isolate->heap()->NumberFromDouble(
+      static_cast<int32_t>(double_to_uint64(x) & 0xFFFFFFFFu));
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_ConstructDouble) {
+  SealHandleScope shs(isolate);
+  ASSERT(args.length() == 2);
+  CONVERT_NUMBER_CHECKED(uint32_t, hi, Uint32, args[0]);
+  CONVERT_NUMBER_CHECKED(uint32_t, lo, Uint32, args[1]);
+  uint64_t result = (static_cast<uint64_t>(hi) << 32) | lo;
+  return isolate->heap()->AllocateHeapNumber(uint64_to_double(result));
+}
+
+
 // Cube root approximation, refer to: http://metamerist.com/cbrt/cbrt.htm
 // Using initial approximation adapted from Kahan's cbrt and 4 iterations
 // of Newton's method.
 inline double CubeRootNewtonIteration(double approx, double x) {
   return (1.0 / 3.0) * (x / (approx * approx) + 2 * approx);
 }
 
 
 inline double CubeRoot(double x) {
   static const uint64_t magic = V8_2PART_UINT64_C(0x2A9F7893, 00000000);
@@ skipping 7300 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal