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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 /manual | |
| parent | e72ef23ee88187284b4b1ca9b2e314e618429d35 (diff) | |
| download | glibc-347a5b592c91f0230d52a5117fd83e1f75028207.zip glibc-347a5b592c91f0230d52a5117fd83e1f75028207.tar.gz glibc-347a5b592c91f0230d52a5117fd83e1f75028207.tar.bz2 | |
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 'manual')
| -rw-r--r-- | manual/math.texi | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/manual/math.texi b/manual/math.texi index 376306c..e00871c 100644 --- a/manual/math.texi +++ b/manual/math.texi @@ -131,9 +131,10 @@ defined. The default set of features includes these constants. @xref{Feature Test Macros}. All values are of type @code{double}. As an extension, @theglibc{} -also defines these constants with type @code{long double}. The -@code{long double} macros have a lowercase @samp{l} appended to their -names: @code{M_El}, @code{M_PIl}, and so forth. These are only +also defines these constants with type @code{long double} and +@code{float}. The @code{long double} macros have a lowercase @samp{l} +while the @code{float} macros have a lowercase @samp{f} appended to +their names: @code{M_El}, @code{M_PIl}, and so forth. These are only available if @code{_GNU_SOURCE} is defined. Likewise, @theglibc{} also defines these constants with the types |