[builtins] Introduce proper Float64Exp operator.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 2332408f167e18d048ea72b2a0874877e5641d13..14b993abbbb4822075f824a569799f1b5c879e51 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -178,11 +178,6 @@ 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;
-
 // -----------------------------------------------------------------------------
 // Implementation of AssemblerBase
 
@@ -1006,61 +1001,6 @@ void ExternalReference::SetUp() {
   double_constants.negative_infinity = -V8_INFINITY;
   double_constants.uint32_bias =
     static_cast<double>(static_cast<uint32_t>(0xFFFFFFFF)) + 1;
-
-  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);
-  if (!math_exp_data_initialized) {
-    // If this is changed, generated code must be adapted too.
-    const int kTableSizeBits = 11;
-    const int kTableSize = 1 << kTableSizeBits;
-    const double kTableSizeDouble = static_cast<double>(kTableSize);
-
-    math_exp_constants_array = new double[9];
-    // Input values smaller than this always return 0.
-    math_exp_constants_array[0] = -708.39641853226408;
-    // Input values larger than this always return +Infinity.
-    math_exp_constants_array[1] = 709.78271289338397;
-    math_exp_constants_array[2] = V8_INFINITY;
-    // The rest is black magic. Do not attempt to understand it. It is
-    // loosely based on the "expd" function published at:
-    // http://herumi.blogspot.com/2011/08/fast-double-precision-exponential.html
-    const double constant3 = (1 << kTableSizeBits) / base::ieee754::log(2.0);
-    math_exp_constants_array[3] = constant3;
-    math_exp_constants_array[4] =
-        static_cast<double>(static_cast<int64_t>(3) << 51);
-    math_exp_constants_array[5] = 1 / constant3;
-    math_exp_constants_array[6] = 3.0000000027955394;
-    math_exp_constants_array[7] = 0.16666666685227835;
-    math_exp_constants_array[8] = 1;
-
-    math_exp_log_table_array = new double[kTableSize];
-    for (int i = 0; i < kTableSize; i++) {
-      double value = std::pow(2, i / kTableSizeDouble);
-      uint64_t bits = bit_cast<uint64_t, double>(value);
-      bits &= (static_cast<uint64_t>(1) << 52) - 1;
-      double mantissa = bit_cast<double, uint64_t>(bits);
-      math_exp_log_table_array[i] = mantissa;
-    }
-
-    math_exp_data_initialized = true;
-  }
-}
-
-
-void ExternalReference::TearDownMathExpData() {
-  delete[] math_exp_constants_array;
-  math_exp_constants_array = NULL;
-  delete[] math_exp_log_table_array;
-  math_exp_log_table_array = NULL;
-  delete math_exp_data_mutex;
-  math_exp_data_mutex = NULL;
 }
 
 
@@ -1353,7 +1293,7 @@ ExternalReference ExternalReference::f64_tan_wrapper_function(
 }
 
 static void f64_exp_wrapper(double* param) {
-  WriteDoubleValue(param, std::exp(ReadDoubleValue(param)));
+  WriteDoubleValue(param, base::ieee754::exp(ReadDoubleValue(param)));
 }
 
 ExternalReference ExternalReference::f64_exp_wrapper_function(
@@ -1628,6 +1568,11 @@ ExternalReference ExternalReference::ieee754_atan2_function(Isolate* isolate) {
       isolate, FUNCTION_ADDR(base::ieee754::atan2), BUILTIN_FP_FP_CALL));
 }
 
+ExternalReference ExternalReference::ieee754_exp_function(Isolate* isolate) {
+  return ExternalReference(
+      Redirect(isolate, FUNCTION_ADDR(base::ieee754::exp), BUILTIN_FP_CALL));
+}
+
 ExternalReference ExternalReference::ieee754_log_function(Isolate* isolate) {
   return ExternalReference(
       Redirect(isolate, FUNCTION_ADDR(base::ieee754::log), BUILTIN_FP_CALL));
@@ -1648,19 +1593,6 @@ ExternalReference ExternalReference::ieee754_log10_function(Isolate* isolate) {
       Redirect(isolate, FUNCTION_ADDR(base::ieee754::log10), BUILTIN_FP_CALL));
 }
 
-ExternalReference ExternalReference::math_exp_constants(int constant_index) {
-  DCHECK(math_exp_data_initialized);
-  return ExternalReference(
-      reinterpret_cast<void*>(math_exp_constants_array + constant_index));
-}
-
-
-ExternalReference ExternalReference::math_exp_log_table() {
-  DCHECK(math_exp_data_initialized);
-  return ExternalReference(reinterpret_cast<void*>(math_exp_log_table_array));
-}
-
-
 ExternalReference ExternalReference::page_flags(Page* page) {
   return ExternalReference(reinterpret_cast<Address>(page) +
                            MemoryChunk::kFlagsOffset);