i965: Fix clear code for ignoring colormask for XRGB formats on Gen9+.
In commit cda886a4, Neil made us stop advertising RGBX formats on Gen9+, as the hardware apparently no longer has working fast clear support for those formats. Instead, we just fall back to RGBA formats, and use SCS to override alpha to 1.0. This is fine, but had one unintended side effect: it made us fall back to slow clears when the color mask disables alpha. Normally, we ignore the color mask for non-existent channels. This includes alpha for XRGB formats as writing garbage to the X channel is harmless. But, now that we use RGBA, we think there's a real alpha channel, and can't do the optimization. To hack around this, check if _BaseFormat is GL_RGB and ignore alpha. Improves WebGL Aquarium performance on Skylake GT3e by about 50% by letting it use repclears instead of slow clears. Cc: mesa-stable@lists.freedesktop.org Signed-off-by:Kenneth Graunke <kenneth@whitecape.org> Reviewed-by:
Ben Widawsky <ben@bwidawsk.net> Reviewed-by:
Topi Pohjolainen <topi.pohjolainen@intel.com> Reviewed-by:
Iago Toral Quiroga <itoral@igalia.com> (cherry picked from commit 73b01e27)
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