On 07/02/2014 06:36 AM, Brian Paul wrote:
On 07/01/2014 08:43 PM, Michel Dänzer wrote:
On 02.07.2014 00:43, Brian Paul wrote:
Module: Mesa
Branch: master
Commit: f4b0ab7afd83c811329211eae8167c9bf238870c
URL:
https://urldefense.proofpoint.com/v1/url?u=http://cgit.freedesktop.org/mesa/mesa/commit/?id%3Df4b0ab7afd83c811329211eae8167c9bf238870c&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=lGQMzzTgII0I7jefp2FHq7WtZ%2BTLs8wadB%2BiIj9xpBY%3D%0A&m=X5dPXUSLXb%2B60RW5%2FHCgcIkPXz083MgfZAbiRJFVOxc%3D%0A&s=c9766b9e3797ccad30888c534fae5891f9a7313418a228c81c0528230412cf1c


Author: Brian Paul <bri...@vmware.com>
Date:   Tue Jul  1 08:17:09 2014 -0600

st/mesa: fix incorrect size of UBO declarations

UniformBufferSize is in bytes so we need to divide by 16 to get the
number of constant buffer slots.  Also, the ureg_DECL_constant2D()
function takes first..last parameters so we need to subtract one
for the last value.

This change broke the GLSL uniform_buffer fs/vs/gs-struct-pad piglit
tests with radeonsi:

../../../../src/gallium/auxiliary/gallivm/lp_bld_tgsi.c:306:lp_build_emit_fetch:
Assertion `reg->Register.Index <=
bld_base->info->file_max[reg->Register.File]' failed.

AFAICT reg->Register.Index is 2, and the new code calls
ureg_DECL_constant2D() with last=1. This is the TGSI code:

FRAG
PROPERTY FS_COLOR0_WRITES_ALL_CBUFS 1
DCL OUT[0], COLOR
DCL CONST[1][0..1]
DCL TEMP[0], LOCAL
IMM[0] UINT32 {0, 16, 32, 0}
   0: MOV TEMP[0].x, CONST[1][0].xxxx
   1: MOV TEMP[0].y, CONST[1][1].xxxx
   2: MOV TEMP[0].z, CONST[1][2].xxxx
   3: MOV TEMP[0].w, CONST[1][2].xxxx
   4: MOV OUT[0], TEMP[0]
   5: END

which results from this GLSL code:

#version 140

struct S1 {
         float r;
};

struct S2 {
         float g;
         float b;
         float a;
};

struct S {
        S1 s1;
        S2 s2;
};

uniform ubo1 {
         S s;
};

void main()
{
         gl_FragColor = vec4(s.s1.r, s.s2.g, s.s2.b, s.s2.a);
}


Something doesn't seem to add up, but I'm not sure where exactly the
problem is or how to fix it.


I think there's at least a one GLSL compiler bug exposed here.

 From the code fragments above, the z and w components of TEMP[0] are
getting the same value when they should not.

I reverted Mesa to before my changes and modified the piglit test to use
different values for the blue/alpha channels and it fails (nvidia
passes).  We were just getting lucky before my changes.

I suspect the code which is laying out the floats in the UBO is doing
something wrong, and the size of the UBO is miscalculated as a result.

I'll dig a bit more but I think someone more familiar with the compiler
will need to help.

The initial IR looks OK:


(loop ...

(assign (xyzw) (var_ref gl_Position) (array_ref (var_ref vertex_to_gs) (var_ref i) ) )
        (declare (temporary ) vec4 vec_ctor)
(assign (x) (var_ref vec_ctor) (record_ref (record_ref (var_ref s) s1) r) ) (assign (y) (var_ref vec_ctor) (record_ref (record_ref (var_ref s) s2) g) ) (assign (z) (var_ref vec_ctor) (record_ref (record_ref (var_ref s) s2) b) ) (assign (w) (var_ref vec_ctor) (record_ref (record_ref (var_ref s) s2) a) )
        (assign  (xyzw) (var_ref v)  (var_ref vec_ctor) )
        (call EmitVertex  ())

... endloop)


But later, after linking, the Z and W components of the vector constructor seem to get merged. Note: there's only 3 ubo_load instructions now instead of four:

...
(assign (xyzw) (var_ref gl_Position) (array_ref (var_ref vertex_to_gs) (constant int (0)) ) )
      (declare (temporary ) vec4 vec_ctor)
      (declare () float cse)
(assign (x) (var_ref cse) (expression float ubo_load (constant uint (0)) (constant uint (0)) ) )
      (assign  (x) (var_ref vec_ctor)  (var_ref cse) )
      (declare () float cse@3)
(assign (x) (var_ref cse@3) (expression float ubo_load (constant uint (0)) (constant uint (16)) ) )
      (assign  (y) (var_ref vec_ctor)  (var_ref cse@3) )
      (declare () float cse@4)
(assign (x) (var_ref cse@4) (expression float ubo_load (constant uint (0)) (constant uint (32)) ) )
      (assign  (z) (var_ref vec_ctor)  (var_ref cse@4) )
      (assign  (w) (var_ref vec_ctor)  (var_ref cse@4) )
      (assign  (xyzw) (var_ref v)  (var_ref vec_ctor) )
      (assign  (xyzw) (var_ref v@5)  (var_ref v) )
      (assign  (xyzw) (var_ref gl_Position@6)  (var_ref gl_Position) )
      (emit-vertex (constant int (0)) )

I'm not sure I can debug this much further right now.

-Brian

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