[Mesa-dev] [PATCH v2 03/52] intel/fs: Handle flag read/write aliasing in needs_src_copy

[Matt Turner]

On 10/12, Jason Ekstrand wrote:
>In order to implement the ballot intrinsic, we do a MOV from flag
>register to some GRF.  If that GRF is used in a SEL, cmod propagation
>helpfully changes it into a MOV from the flag register with a cmod.
>This is perfectly valid but when lower_simd_width comes along, it simply
>splits into two instructions which both have conditional modifiers.
>This is a problem since we're reading the flag register.  This commit
>makes us check whether or not flags_written() overlaps with the flag
>values that we are reading via the instruction source and, if we have
>any interference, will force us to emit a copy of the source.
>
>Cc: mesa-stable at lists.freedesktop.org

Reviewed-by: Matt Turner <mattst88 at gmail.com>
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