i965: fix alpha test for MRT
Include src0 alpha in the RT write message when using MRT, so it is used
for the alpha test instead of the normal per-RT alpha value.
Fixes broken rendering in Dota2 under Wine [FDO #62647].
No Piglit regressions on Ivybridge.
V2: reuse (and simplify) existing sample_alpha_to_coverage flag in
the FS key, rather than adding another redundant one.
Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewd-by: Paul Berry <stereotype441@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=62647
NOTE: This is a candidate for the stable branches.
4 files changed
