[Mesa-dev] [PATCH 15/14] i965/fs: Don't emit 16-wide BFI1 instructions.

[Eric Anholt]

Matt Turner <mattst88 at gmail.com> writes:

> The Haswell Bspec says "A SIMD16 instruction is not allowed." (but
> 16-wide BFI1 works for me so far). Since GLSL's bitfieldInsert()
> function takes int parameters BFI1 produces the same results in all
> channels, so there's never any reason to emit a 16-wide BFI1.

Suppose the first 8 pixels didn't take a branch, while the second 8 did,
and you're bitfield inserting in this branch.  You'd be using undefined
values for src[0].
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