https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96482
--- Comment #5 from Yevhenii Kolesnikov <yevh.kolesnikov at gmail dot com> ---
(In reply to Martin Liška from comment #3)
> Thank you for the report, I can take a look.
> Can you please provide steps how to build Mesa with -O3 and -flto?
mesa is configured with meson. LTO can be enabled with builtin option
-b_lto=true. Options can be supplied to the compiler with -Dc_args and
-Dcpp_args. So, to enable O3 it's -Dc_args="-O3" -Dcpp_args="-O3". You'll also
need to set -Dbuildtype=plain, or otherwise these options will be overwritten.
So, the full build process will look like this:
meson \
-Dbuildtype=plain \
-Dvalgrind=false \
-Ddri-drivers=i965 \
-Dgallium-drivers=iris,swrast \
-Dvulkan-drivers= \
-Dgallium-omx="disabled" \
-Dplatforms=x11,drm,surfaceless \
-Dllvm=false \
-Db_lto=true \
-Dc_args="-g \
-O3 \
" \
-Dcpp_args="-g \
-O3 \
" \
--prefix=~/builds/mesa-bug \
./mesa-bug
ninja -C ./mesa-bug install
The aforementioned functions and assembly code then will be in
~/builds/mesa-bug/lib/dri/iris_dri.so
> About the addr_to_index function: am I right that unreachable is defined in
> your configuration as __builtin_unreachable?
To be precise, unreachable is defined like this:
#define unreachable(str) \
do { \
assert(!str); \
__builtin_unreachable(); \
} while (0)
I'm not sure why this one-time loop is necessary, to be honest.
> Can you please replace it with fprintf that prints the value?
The value of addr_format? It doesn't print anything, since this branch is never
hit. Moreover, it prevents addr_to_index from being inlined, so the crash goes
away. The value of addr_format in my case is 3, which corresponds to the
nir_address_format_32bit_index_offset enum. So, in my case, the first branch is
always hit.
