[Mesa-dev] [PATCH 1/2] nvc0/ir: detect AND/SHR pairs and convert into EXTBF

Matt Turner mattst88 at gmail.com
Tue Aug 18 18:58:14 PDT 2015

On Tue, Aug 18, 2015 at 6:57 PM, Matt Turner <mattst88 at gmail.com> wrote:
> On Tue, Aug 18, 2015 at 6:49 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>> Some shaders appear to extract bits using shift/and combos. Detect
>> (some) of those and convert to EXTBF instead.
> What is EXTBF? Extract byte to float?
> I ask because Unigine Heaven has shaders that pack 3x byte-integers
> into one component of a vec4 and extracts them with shifts/ands and
> converts them to floats, and i965 could do the extraction and
> conversion in a single instruction. I'm curious if this is the same
> thing you're optimizing.

Well, I apparently just needed to read your second patch's commit
message to confirm my suspicions.

> I thought about adding an extract_byte(src, byte_num) operation, but
> i965's copy propagation caused me some headache and I shelved it.

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