cf265c6606
On iris and crocus, this flag is used to set "alt mode" math on the shader as a whole. Some other drivers have a similar mode for DX9/ARB-program behavior, so document what it does so we can start using it. Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16176>