[turbofan] Implement rounding of floats on x64 and ia32 without sse4.1.

src/assembler.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 131 matching lines @@
 // -----------------------------------------------------------------------------
 // Common double constants.
 
 struct DoubleConstant BASE_EMBEDDED {
 double min_int;
 double one_half;
 double minus_one_half;
 double negative_infinity;
 double the_hole_nan;
 double uint32_bias;
+double rounding_limit;
 };
 
 static DoubleConstant double_constants;
 
 const char* const RelocInfo::kFillerCommentString = "DEOPTIMIZATION PADDING";
 
 static bool math_exp_data_initialized = false;
 static base::Mutex* math_exp_data_mutex = NULL;
 static double* math_exp_constants_array = NULL;
 static double* math_exp_log_table_array = NULL;
@@ skipping 781 matching lines @@
 // Implementation of ExternalReference
 
 void ExternalReference::SetUp() {
   double_constants.min_int = kMinInt;
   double_constants.one_half = 0.5;
   double_constants.minus_one_half = -0.5;
   double_constants.the_hole_nan = bit_cast<double>(kHoleNanInt64);
   double_constants.negative_infinity = -V8_INFINITY;
   double_constants.uint32_bias =
     static_cast<double>(static_cast<uint32_t>(0xFFFFFFFF)) + 1;
+  // 2^52;
+  double_constants.rounding_limit = 4503599627370496.0;
 
   math_exp_data_mutex = new base::Mutex();
 }
 
 
 void ExternalReference::InitializeMathExpData() {
   // Early return?
   if (math_exp_data_initialized) return;
 
   base::LockGuard<base::Mutex> lock_guard(math_exp_data_mutex);
@@ skipping 307 matching lines @@
       reinterpret_cast<void*>(&double_constants.the_hole_nan));
 }
 
 
 ExternalReference ExternalReference::address_of_uint32_bias() {
   return ExternalReference(
       reinterpret_cast<void*>(&double_constants.uint32_bias));
 }
 
 
+ExternalReference ExternalReference::address_of_rounding_limit() {
+  return ExternalReference(
+      reinterpret_cast<void*>(&double_constants.rounding_limit));
+}
+
+
 ExternalReference ExternalReference::is_profiling_address(Isolate* isolate) {
   return ExternalReference(isolate->cpu_profiler()->is_profiling_address());
 }
 
 
 ExternalReference ExternalReference::invoke_function_callback(
     Isolate* isolate) {
   Address thunk_address = FUNCTION_ADDR(&InvokeFunctionCallback);
   ExternalReference::Type thunk_type = ExternalReference::PROFILING_API_CALL;
   ApiFunction thunk_fun(thunk_address);
@@ skipping 562 matching lines @@
 
 
 void Assembler::DataAlign(int m) {
   DCHECK(m >= 2 && base::bits::IsPowerOfTwo32(m));
   while ((pc_offset() & (m - 1)) != 0) {
     db(0);
   }
 }
 }  // namespace internal
 }  // namespace v8