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/*========================== begin_copyright_notice ============================
Copyright (C) 2017-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
#include "../include/BiF_Definitions.cl"
#include "../../Headers/spirv.h"
#if defined(cl_khr_fp64)
#include "../IMF/FP64/exp_d_la.cl"
#include "../IMF/FP64/exp_d_la_noLUT.cl"
#endif // defined(cl_khr_fp64)
float SPIRV_OVERLOADABLE SPIRV_OCL_BUILTIN(exp, _f32, )(float x)
{
if (__FastRelaxedMath)
{
return SPIRV_OCL_BUILTIN(native_exp, _f32, )(x);
}
else
{
// e^x = 2^(log2(e^x)) = 2^(x * log2(e))
// We'll compute 2^(x * log2(e)) by splitting x * log2(e)
// into a whole part and fractional part.
// Compute the whole part of x * log2(e)
// This part is easy!
float w = SPIRV_OCL_BUILTIN(trunc, _f32, )( x * M_LOG2E_F );
// Compute the fractional part of x * log2(e)
// We have to do this carefully, so we don't lose precision.
// Compute as:
// fract( x * log2(e) ) = ( x - w * C1 - w * C2 ) * log2(e)
// C1 is the "Cephes Constant", and is close to 1/log2(e)
// C2 is the difference between the "Cephes Constant" and 1/log2(e)
const float C1 = as_float( 0x3F317200 ); // 0.693145751953125
const float C2 = as_float( 0x35BFBE8E ); // 0.000001428606765330187
float f = x;
f = SPIRV_OCL_BUILTIN(fma, _f32_f32_f32, )( w, -C1, f );
f = SPIRV_OCL_BUILTIN(fma, _f32_f32_f32, )( w, -C2, f );
f = f * M_LOG2E_F;
w = SPIRV_OCL_BUILTIN(native_exp2, _f32, )( w ); // this should be exact
f = SPIRV_OCL_BUILTIN(native_exp2, _f32, )( f ); // this should be close enough
float res = w * f;
res = ( x < as_float( 0xC2D20000 ) ) ? as_float( 0x00000000 ) : res;
res = ( x > as_float( 0x42D20000 ) ) ? as_float( 0x7F800000 ) : res;
return res;
}
}
GENERATE_SPIRV_OCL_VECTOR_FUNCTIONS_1ARGS( exp, float, float, f32 )
#if defined(cl_khr_fp64)
INLINE double SPIRV_OVERLOADABLE SPIRV_OCL_BUILTIN(exp, _f64, )( double x )
{
double result;
if (__UseHighAccuracyMath) {
result = __ocl_svml_exp_noLUT(x);
} else {
result = __ocl_svml_exp(x);
}
return result;
}
GENERATE_SPIRV_OCL_VECTOR_FUNCTIONS_1ARG_LOOP( exp, double, double, f64 )
#endif // defined(cl_khr_fp64)
#if defined(cl_khr_fp16)
INLINE half SPIRV_OVERLOADABLE SPIRV_OCL_BUILTIN(exp, _f16, )( half x )
{
return SPIRV_OCL_BUILTIN(exp, _f32, )((float)x);
}
GENERATE_SPIRV_OCL_VECTOR_FUNCTIONS_1ARGS( exp, half, half, f16 )
#endif // defined(cl_khr_fp16)
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