Re: [Qemu-devel] [PATCH v3 1.3] build: compile translate.o with -fno-gcse option on GCC 4.6.x and 4.7.[012]

["Andreas Färber" <afaerber@suse.de>]

Am 28.11.2012 09:40, schrieb Paolo Bonzini:
> These versions of GCC require insane (>2GB) amounts of memory to compile
> translate.o.  As a countermeasure, disable the culprit optimization pass.
> This should fix the buildbot failure for default_x86_64_fedora16.  Anyway
> this is a good thing to do because people will try to compile 1.3 with
> less than 2GB of memory and complain.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Tested-by: Andreas Färber <afaerber@suse.de>

> ---
>  Makefile.target |  3 +++
>  configure       | 16 ++++++++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/Makefile.target b/Makefile.target
> index 8b658c0..927347b 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -143,6 +143,9 @@ GENERATED_HEADERS += hmp-commands.h qmp-commands-old.h
>  
>  endif # CONFIG_SOFTMMU
>  
> +# Workaround for http://gcc.gnu.org/PR55489, see configure.
> +%/translate.o: QEMU_CFLAGS += $(TRANSLATE_OPT_CFLAGS)
> +
>  nested-vars += obj-y
>  
>  # This resolves all nested paths, so it must come last
> diff --git a/configure b/configure
> index 780b19a..994f731 100755
> --- a/configure
> +++ b/configure
> @@ -1183,6 +1183,21 @@ for flag in $gcc_flags; do
>      fi
>  done
>  
> +# Workaround for http://gcc.gnu.org/PR55489.  Happens with -fPIE/-fPIC and
> +# large functions that use global variables.  The bug is in all releases of
> +# GCC, but it became particularly acute in 4.6.x and 4.7.x.  It is fixed in
> +# 4.7.3 and 4.8.0.  We should be able to delete this at the end of 2013.
> +cat > $TMPC << EOF
> +#if __GNUC__ == 4 && (__GNUC_MINOR__ == 6 || (__GNUC_MINOR__ == 7 && __GNUC_PATCHLEVEL__ <= 2))

FWIW this line looks overly long.

> +int main(void) { return 0; }
> +#else
> +#error No bug in this compiler.

Interesting logic. :)

Andreas

> +#endif
> +EOF
> +if compile_prog "-Werror -fno-gcse" "" ; then
> +  TRANSLATE_OPT_CFLAGS=-fno-gcse
> +fi
> +
>  if test "$static" = "yes" ; then
>    if test "$pie" = "yes" ; then
>      echo "static and pie are mutually incompatible"
> @@ -3662,6 +3677,7 @@ echo "LIBS_TOOLS+=$libs_tools" >> $config_host_mak
>  echo "EXESUF=$EXESUF" >> $config_host_mak
>  echo "LIBS_QGA+=$libs_qga" >> $config_host_mak
>  echo "POD2MAN=$POD2MAN" >> $config_host_mak
> +echo "TRANSLATE_OPT_CFLAGS=$TRANSLATE_OPT_CFLAGS" >> $config_host_mak
>  
>  # generate list of library paths for linker script
>  
> 


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