[Nouveau] [Bug 96355] Performance: extra&costly SSBO validation even when SSBO aren't used

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96355

--- Comment #3 from gregory.hainaut at gmail.com ---
Hi Samuel,

> Thanks for profiling Nouveau with perf, that's very nice. :-)

Well it is nice that I can do profiling :)

> Well, if your application doesn't use SSBO's, nvc0_validate_buffers() 
> should not be called yeah. But this might happen when we switch between
>  different contexts. Anyway, improving the validation path is on our todolist. :)

Yes, I'm sure. I don't know how to use SSBO.

> I wonder why it's called if you are sure that your application doesn't use
> any SSBO's...

src/mesa/state_tracker/st_atom_storagebuf.c
st_bind_*_ssbos struct contains the ST_NEW_*_PROGRAM flags.

So every time, you call glUseProgram (or the 4.1 pipeline equivalent), flags
will be asserted and a validation will be triggered. It is the same for the
image in st_bind_*_images struct in st_atom_image.c. It is nice for the
performance.

> Can you extract some shaders from your application to make sure no SSBO's 
> are used? You can use NV50_PROG_DEBUG=1 for example (this will dump the TGSI code).

All my shader could be found in glsl format (bit a mess of ifdef but no SSBO
;))
https://github.com/PCSX2/pcsx2/tree/master/plugins/GSdx/res/glsl

Here an example (I'm not sure if it is the TGSI format).

FRAG
DCL IN[0], GENERIC[0], PERSPECTIVE
DCL IN[1], GENERIC[3], PERSPECTIVE
DCL OUT[0], COLOR
DCL OUT[1], COLOR[1]
DCL SAMP[0]
DCL SAMP[1]
DCL SVIEW[0], 2D, FLOAT
DCL SVIEW[1], 2D, FLOAT
DCL CONST[1][0]
DCL CONST[2][0..1]
DCL CONST[3][0..1]
DCL CONST[4][0]
DCL CONST[5][0..1]
DCL CONST[6][0..7]
DCL CONST[7][0]
DCL TEMP[0..1], LOCAL
IMM[0] FLT32 {    0.0000,   255.0000,     0.0500,     0.0078}
IMM[1] FLT32 {    0.0039,     0.0000,     0.0000,     0.0000}
  0: MOV TEMP[0].xy, IN[1].xyyy
  1: TEX TEMP[0].w, TEMP[0], SAMP[0], 2D
  2: MOV TEMP[1].y, IMM[0].xxxx
  3: MOV TEMP[1].x, TEMP[0].wwww
  4: TRUNC TEMP[0], IN[0]
  5: MOV TEMP[1].xy, TEMP[1].xyyy
  6: TEX TEMP[1], TEMP[1], SAMP[1], 2D
  7: MAD TEMP[1], TEMP[1], IMM[0].yyyy, IMM[0].zzzz
  8: TRUNC TEMP[1], TEMP[1]
  9: MUL TEMP[0], TEMP[0], TEMP[1]
 10: MUL TEMP[0], TEMP[0], IMM[0].wwww
 11: TRUNC TEMP[0], TEMP[0]
 12: MIN TEMP[0], TEMP[0], IMM[0].yyyy
 13: MUL TEMP[1], TEMP[0], IMM[1].xxxx
 14: MUL TEMP[0].x, TEMP[0].wwww, IMM[0].wwww
 15: MOV OUT[0], TEMP[1]
 16: MOV OUT[1], TEMP[0].xxxx
 17: END

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