Patrick Lerda e8fa3b4950 r600: make vertex r10g10b10a2_snorm conformant on palm and beyond
The mode r10g10b10a2_snorm processed as vertex on palm at the
hardware level doesn't follow the current standard. Indeed, the .w
component (2-bits) is not calculated as expected. The table below
describes the situation.

This change fixes this issue by adding three gpu instructions at
the vertex fetch shader stage. An equivalent C representation and
a gpu asm dump of the generated sequence are available below.

.w(2-bits) expected	palm
0	    0.0		0.000000
1 	    1.0		0.333333
2	   -1.0		0.666667
3	   -1.0		1.000000

w_out = (4.*w_in > 1. ? 1. : 4.*w_in) - (w_in > 0.5 ? 2. : 0.);

0002 00000008 A0080000  ALU 3 @16
 0016 00000C02 A0000CC0     1 y:     MOV*4_sat              __.y,  R2.w
 0018 801F8C02 600004A0       w:     SETGT*2                __.w,  R2.w, 0.5
 0020 839FC4FE 60400010     2 w:     ADD                    R2.w,  PV.y, -PV.w

Note: The rv770 and cypress don't need this correction. This is
definitely a hardware change between these gpus.

This change was tested on palm, barts and cayman. Here are the tests fixed:
spec/arb_vertex_type_2_10_10_10_rev/arb_vertex_type_2_10_10_10_rev-array_types: fail pass
deqp-gles3/functional/draw/random/124: fail pass
deqp-gles3/functional/vertex_arrays/single_attribute/normalize/int2_10_10_10/components4_quads1: fail pass
deqp-gles3/functional/vertex_arrays/single_attribute/normalize/int2_10_10_10/components4_quads256: fail pass
khr-gl43/vertex_attrib_binding/basic-input-case5: fail pass
khr-gl44/vertex_attrib_binding/basic-input-case5: fail pass
khr-gl45/vertex_attrib_binding/basic-input-case5: fail pass

Cc: mesa-stable
Signed-off-by: Patrick Lerda <patrick9876@free.fr>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32427>
2025-06-23 11:56:11 +00:00
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`Mesa <https://mesa3d.org>`_ - The 3D Graphics Library
======================================================


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