[Mesa-dev] Mesa (master): mesa: document instructions ir_to_mesa emits

Marek Olšák maraeo at gmail.com
Mon May 9 15:55:14 PDT 2011

On Tue, May 10, 2011 at 12:00 AM, Ian Romanick <idr at freedesktop.org> wrote:
> Hash: SHA1
> On 05/09/2011 11:03 AM, Marek Olšák wrote:
>> Module: Mesa
>> Branch: master
>> Commit: 801fbdf286bed58435ca3a9008104b098717ed9b
>> URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=801fbdf286bed58435ca3a9008104b098717ed9b
>> Author: Marek Olšák <maraeo at gmail.com>
>> Date:   Mon May  9 18:18:56 2011 +0200
>> mesa: document instructions ir_to_mesa emits
>> GLSL stopped using:
>>    BRA, EXP, LOG, LRP, NRM3, NRM4, XPD.
>> GLSL started using:
>>    KIL, SCS, SSG, SWZ.
>> (omg why SWZ? isn't proc_src_register flexible enough?)
> The problem is that some architectures (e.g., Nvidia, i965) can only use
> that flexibility with the special SWZ instruction.  As far as I'm aware,
> the back-ends for architectures that can use that flexibility (e.g.,
> i915) aren't expecting it.  I'm not sure prog_exec will work with that
> either.
>> GLSL doesn't use these opcodes some Radeons do support:
>>    ARR, DP2A, DST, LRP, XPD.
>> These opcodes are now unused:
>>    AND, NOT, NRM3, NRM4, OR, XOR.
>> (plus maybe the NV extensions which are unused by Gallium)
>> In addition to that, we don't use two-dimensional indirect addressing,
>> which the Mesa IR can do.
> You mean things like:
>        MOV     R0, array[A0.x + 5];

prog_src_register::RelAddr2 surprised me so much that I didn't see the
comment in front of it. :) It seems to be for geometry shaders. The
expected usage is INPUT[vertex_index][attrib_index].


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