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| author | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-12-31 09:50:50 +0000 |
|---|---|---|
| committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2022-01-10 14:27:17 +0000 |
| commit | 347a5b592c91f0230d52a5117fd83e1f75028207 (patch) | |
| tree | cef1eb7585b59b17118ad72f82856b39f94cfd14 /math/math.h | |
| parent | e72ef23ee88187284b4b1ca9b2e314e618429d35 (diff) | |
| download | glibc-347a5b592c91f0230d52a5117fd83e1f75028207.tar.gz glibc-347a5b592c91f0230d52a5117fd83e1f75028207.tar.xz glibc-347a5b592c91f0230d52a5117fd83e1f75028207.zip | |
math: Fix float conversion regressions with gcc-12 [BZ #28713]
Converting double precision constants to float is now affected by the runtime dynamic rounding mode instead of being evaluated at compile time with default rounding mode (except static object initializers). This can change the computed result and cause performance regression. The known correctness issues (increased ulp errors) are already fixed, this patch fixes remaining cases of unnecessary runtime conversions. Add float M_* macros to math.h as new GNU extension API. To avoid conversions the new M_* macros are used and instead of casting double literals to float, use float literals (only required if the conversion is inexact). The patch was tested on aarch64 where the following symbols had new spurious conversion instructions that got fixed: __clog10f __gammaf_r_finite@GLIBC_2.17 __j0f_finite@GLIBC_2.17 __j1f_finite@GLIBC_2.17 __jnf_finite@GLIBC_2.17 __kernel_casinhf __lgamma_negf __log1pf __y0f_finite@GLIBC_2.17 __y1f_finite@GLIBC_2.17 cacosf cacoshf casinhf catanf catanhf clogf gammaf_positive Fixes bug 28713. Reviewed-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>
Diffstat (limited to 'math/math.h')
| -rw-r--r-- | math/math.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/math/math.h b/math/math.h index 7bd56c9648..27963ef6dc 100644 --- a/math/math.h +++ b/math/math.h @@ -1158,6 +1158,23 @@ iszero (__T __val) # define M_SQRT1_2 0.70710678118654752440 /* 1/sqrt(2) */ #endif +/* GNU extension to provide float constants with similar names. */ +#ifdef __USE_GNU +# define M_Ef 2.7182818284590452354f /* e */ +# define M_LOG2Ef 1.4426950408889634074f /* log_2 e */ +# define M_LOG10Ef 0.43429448190325182765f /* log_10 e */ +# define M_LN2f 0.69314718055994530942f /* log_e 2 */ +# define M_LN10f 2.30258509299404568402f /* log_e 10 */ +# define M_PIf 3.14159265358979323846f /* pi */ +# define M_PI_2f 1.57079632679489661923f /* pi/2 */ +# define M_PI_4f 0.78539816339744830962f /* pi/4 */ +# define M_1_PIf 0.31830988618379067154f /* 1/pi */ +# define M_2_PIf 0.63661977236758134308f /* 2/pi */ +# define M_2_SQRTPIf 1.12837916709551257390f /* 2/sqrt(pi) */ +# define M_SQRT2f 1.41421356237309504880f /* sqrt(2) */ +# define M_SQRT1_2f 0.70710678118654752440f /* 1/sqrt(2) */ +#endif + /* The above constants are not adequate for computation using `long double's. Therefore we provide as an extension constants with similar names as a GNU extension. Provide enough digits for the 128-bit IEEE quad. */ |