On Mon, Sep 3, 2012 at 11:29 AM, Georg-Johann Lay <a...@gjlay.de> wrote: > AVR-Libc comes with hand-optimized float support functions written > in assembler. These functions use the same naming conventions like > libgcc. There are situations where this name clashed lead to performance > regression because the functions from libgcc are linked. One example > are the new fixed-point support that convert fixed-point to/from float > and reference float/int conversion functions from within libgcc. > > The float implementation in libm.a have been discussed several times > with the only result that it is very unlikely that the code will > ever be integrated into libgcc because the original authors are no > more around. And is is much less work to add a new configure switch > than to port and integrate the code, given there were no license issues. > One point against such an extension was that such change to the compiler > establishes a dependency between the compiler and AVR-Libc, but this > decision has been made long ago by accepting code that actually should > had been added to libgcc -- but was not for whatever reason. > > This patch removes that performance regressions by removing the > doubly implemented functions from libgcc by means of a new configure > option --with-avrlibc.
Johann, as I stated yesterday, I do not understand why there needs to be yet another configure option. The NATURAL libc for ARV targets is ARV-libc. We should not need a switch for that. -- Gaby > > Moreover, some specs are adjusted so that -lm is treated very much like > -lgcc so that the user need not specify -lm by hand for core float > support like int/float conversions. > > Without this patch, LTO compilations also lead to performance regression > because lto adds -plugin-opt=-pass-through=-lgcc etc. prior to the -lm > specified by the user. > > Other cases where code is improved are C++ programs, see PR28718 for a > discussion. > > > There are less fails in gcc.dg/fixed-point, presumably because the rounding > is as expected by the test cases, i.e. there are no rounding errors as > mentioned in the review for PR54222: > http://gcc.gnu.org/ml/gcc-patches/2012-08/msg01586.html > > Ok to install? > > > Johann > > > PR target/54461 > * configure.ac (noconfigdirs,target=avr-*-*): Add target-newlib, > target-libgloss if configured --with-avrlibc. > * configure: Regenerate. > > libgcc/ > PR target/54461 > * config.host (tmake_file,host=avr-*-*): Add avr/t-avrlibc if > configured --with-avrlibc. > * config/avr/t-avrlibc: New file. > > gcc/ > PR target/54461 > * config.gcc (tm_file,target=avr-*-*): Add avr/avrlibc.h if > configured --with-avrlibc. > (tm_defines,target=avr-*-*): Add WITH_AVRLIBC if configured > --with-avrlibc. > * config/avr/avrlibc.h: New file. > * config/avr/avr-c.c: Build-in define __WITH_AVRLIBC__ if > configured --with-avrlibc.
