From 347a5b592c91f0230d52a5117fd83e1f75028207 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Fri, 31 Dec 2021 09:50:50 +0000 Subject: 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 --- manual/math.texi | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'manual') diff --git a/manual/math.texi b/manual/math.texi index 376306cfc5..e00871c303 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 -- cgit 1.4.1