[Mesa-dev] [PATCH v2 1/3] i965: add FS_OPCODE_OVERWRITE_DST

[Eric Anholt]

Chia-I Wu <olvaffe at gmail.com> writes:

> From: Chia-I Wu <olv at lunarg.com>
>
> FS_OPCODE_OVERWRITE_DST is used to indicate that the destination register is
> (completely) overwritten.  No code is emitted, but the liveness analysis can
> use it as a hint to add the destination register to DEF bitset.  This is
> needed because it is hard to figure out if some partial writes combined
> constitute a complete write during liveness analysis, while it is easier for
> the FS visitor to know if that is the case.

Note that FS_OPCODE_OVERWRITE_DST should be avoidable now that
texture-grf is landed -- the live intervals calculation is a lot
smarter, and shouldn't take much more work to handle the setup of the
two halves in 16-wide.
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