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fast_math: selectively use GCC rounding builtins when available

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Add a new macro definition OPENCV_USE_FASTMATH_GCC_BUILTINS to enable
usage of GCC inline math functions, if available and requested by the
user.

Likewise, enable it for POWER. This is nearly always a substantial
improvement over using integer manipulation as most operations can
be done in several instructions with no branching. The result is a
1.5-1.8x speedup in the ceil/floor operations.

1. As tested with AT 12.0-1 (GCC 8.3.1) compiler on P9 LE.
This commit is contained in:
Paul E. Murphy 2019-07-22 14:23:49 -05:00
parent b2135be594
commit 3f92bcc11a
1 changed files with 29 additions and 0 deletions
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29
modules/core/include/opencv2/core/fast_math.hpp
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@ -92,6 +92,19 @@
#define ARM_ROUND_FLT(value) ARM_ROUND(value, "vcvtr.s32.f32 %[temp], %[value]\n vmov %[res], %[temp]")
#endif
#if defined __PPC64__ && !defined OPENCV_USE_FASTMATH_GCC_BUILTINS
/* Let GCC inline C math functions when available. Dedicated hardware is available to
round and covert FP values. */
#define OPENCV_USE_FASTMATH_GCC_BUILTINS
#endif
/* Enable GCC builtin math functions if possible, desired, and available.
Note, not all math functions inline equally. E.g lrint will not inline
without the -fno-math-errno option. */
#if defined OPENCV_USE_FASTMATH_GCC_BUILTINS && defined __GNUC__ && !defined __clang__ && !defined (__CUDACC__)
#define _OPENCV_FASTMATH_ENABLE_GCC_MATH_BUILTINS
#endif
/** @brief Rounds floating-point number to the nearest integer
@param value floating-point number. If the value is outside of INT_MIN ... INT_MAX range, the
@ -138,8 +151,12 @@ cvRound( double value )
*/
CV_INLINE int cvFloor( double value )
{
#if defined _OPENCV_FASTMATH_ENABLE_GCC_MATH_BUILTINS
return __builtin_floor(value);
#else
int i = (int)value;
return i - (i > value);
#endif
}
/** @brief Rounds floating-point number to the nearest integer not smaller than the original.
@ -151,8 +168,12 @@ CV_INLINE int cvFloor( double value )
*/
CV_INLINE int cvCeil( double value )
{
#if defined _OPENCV_FASTMATH_ENABLE_GCC_MATH_BUILTINS
return __builtin_ceil(value);
#else
int i = (int)value;
return i + (i < value);
#endif
}
/** @brief Determines if the argument is Not A Number.
@ -225,8 +246,12 @@ CV_INLINE int cvRound( int value )
/** @overload */
CV_INLINE int cvFloor( float value )
{
#if defined _OPENCV_FASTMATH_ENABLE_GCC_MATH_BUILTINS
return __builtin_floorf(value);
#else
int i = (int)value;
return i - (i > value);
#endif
}
/** @overload */
@ -238,8 +263,12 @@ CV_INLINE int cvFloor( int value )
/** @overload */
CV_INLINE int cvCeil( float value )
{
#if defined _OPENCV_FASTMATH_ENABLE_GCC_MATH_BUILTINS
return __builtin_ceilf(value);
#else
int i = (int)value;
return i + (i < value);
#endif
}
/** @overload */