[Piglit] [PATCH] Reproduce a constant propagation bug in Mesa (indexing into vectors).

[Jose Fonseca]

Yep. I still couldn't find a way of using signature/templates effectively for these tags, so end up avoid typing them, but here it is: 

Reviewed-by: Jose Fonseca <jfonseca at vmware.com> 

Jose 

----- Original Message -----

> On 19 May 2012 13:05, Jose Fonseca < jfonseca at vmware.com > wrote:

> > Good find and nice test IMO.
> 

> > Jose
> 

> Thanks, Jose. Can I consider that a "reviewed-by"?

> > ----- Original Message -----
> 
> > > As of 5/19/12, Mesa's constant propagation optimization pass
> > > fails
> > > to
> 
> > > properly account for the behaviour of array indexing applied to
> 
> > > vectors. If v is a vector and i is an integer, it assumes that
> 
> > >
> 
> > > v[i] = ...;
> 
> > >
> 
> > > kills the x component of v. This is not necessarily the case--it
> 
> > > might kill any component of v, depending on the value of i.
> 
> > > ---
> 
> > > ...-vector-indexing-kills-all-channels.shader_test | 39
> 
> > > +++++++++++++++++++
> 
> > > ...-vector-indexing-kills-all-channels.shader_test | 41
> 
> > > ++++++++++++++++++++
> 
> > > 2 files changed, 80 insertions(+), 0 deletions(-)
> 
> > > create mode 100644
> 
> > > tests/spec/glsl-1.10/execution/fs-vector-indexing-kills-all-channels.shader_test
> 
> > > create mode 100644
> 
> > > tests/spec/glsl-1.10/execution/vs-vector-indexing-kills-all-channels.shader_test
> 
> > >
> 
> > > diff --git
> 
> > > a/tests/spec/glsl-1.10/execution/fs-vector-indexing-kills-all-channels.shader_test
> 
> > > b/tests/spec/glsl-1.10/execution/fs-vector-indexing-kills-all-channels.shader_test
> 
> > > new file mode 100644
> 
> > > index 0000000..b22405a
> 
> > > --- /dev/null
> 
> > > +++
> 
> > > b/tests/spec/glsl-1.10/execution/fs-vector-indexing-kills-all-channels.shader_test
> 
> > > @@ -0,0 +1,39 @@
> 
> > > +# This test exercises a bug in mesa as of 5/19.12: constant
> 
> > > +# propagation fails to detect that array indexing into a vector
> 
> > > might
> 
> > > +# kill any component of the vector.
> 
> > > +
> 
> > > +[vertex shader]
> 
> > > +void main()
> 
> > > +{
> 
> > > + gl_Position = gl_Vertex;
> 
> > > +}
> 
> > > +
> 
> > > +[fragment shader]
> 
> > > +#define RED vec4(1.0, 0.0, 0.0, 0.0)
> 
> > > +#define GREEN vec4(0.0, 1.0, 0.0, 0.0)
> 
> > > +
> 
> > > +uniform int three;
> 
> > > +uniform float five;
> 
> > > +
> 
> > > +void main()
> 
> > > +{
> 
> > > + vec4 v = vec4(1.0, 2.0, 3.0, 4.0);
> 
> > > +
> 
> > > + // If the bug is present, constant propagation will see a
> > > scalar
> 
> > > on
> 
> > > + // the RHS, and incorrectly conclude that therefore only v.x is
> 
> > > + // killed.
> 
> > > + v[three] = five;
> 
> > > +
> 
> > > + vec4 color = v.a == 5.0 ? GREEN : RED;
> 
> > > +
> 
> > > + // If the bug is present, then index and new_value will be
> 
> > > optimized
> 
> > > + // away, making shader_runner fail to assign uniforms. To avoid
> 
> > > + // that, multiply color by (five - three - 1.0).
> 
> > > + gl_FragColor = color * (five - float(three) - 1.0);
> 
> > > +}
> 
> > > +
> 
> > > +[test]
> 
> > > +uniform int three 3
> 
> > > +uniform float five 5.0
> 
> > > +draw rect -1 -1 2 2
> 
> > > +probe all rgba 0.0 1.0 0.0 0.0
> 
> > > diff --git
> 
> > > a/tests/spec/glsl-1.10/execution/vs-vector-indexing-kills-all-channels.shader_test
> 
> > > b/tests/spec/glsl-1.10/execution/vs-vector-indexing-kills-all-channels.shader_test
> 
> > > new file mode 100644
> 
> > > index 0000000..6838f78
> 
> > > --- /dev/null
> 
> > > +++
> 
> > > b/tests/spec/glsl-1.10/execution/vs-vector-indexing-kills-all-channels.shader_test
> 
> > > @@ -0,0 +1,41 @@
> 
> > > +# This test exercises a bug in mesa as of 5/19/12: constant
> 
> > > +# propagation fails to detect that array indexing into a vector
> 
> > > might
> 
> > > +# kill any component of the vector.
> 
> > > +
> 
> > > +[vertex shader]
> 
> > > +#define RED vec4(1.0, 0.0, 0.0, 0.0)
> 
> > > +#define GREEN vec4(0.0, 1.0, 0.0, 0.0)
> 
> > > +
> 
> > > +uniform int three;
> 
> > > +uniform float five;
> 
> > > +
> 
> > > +void main()
> 
> > > +{
> 
> > > + gl_Position = gl_Vertex;
> 
> > > +
> 
> > > + vec4 v = vec4(1.0, 2.0, 3.0, 4.0);
> 
> > > +
> 
> > > + // If the bug is present, constant propagation will see a
> > > scalar
> 
> > > on
> 
> > > + // the RHS, and incorrectly conclude that therefore only v.x is
> 
> > > + // killed.
> 
> > > + v[three] = five;
> 
> > > +
> 
> > > + vec4 color = v.a == 5.0 ? GREEN : RED;
> 
> > > +
> 
> > > + // If the bug is present, then index and new_value will be
> 
> > > optimized
> 
> > > + // away, making shader_runner fail to assign uniforms. To avoid
> 
> > > + // that, multiply color by (five - three - 1.0).
> 
> > > + gl_FrontColor = color * (five - float(three) - 1.0);
> 
> > > +}
> 
> > > +
> 
> > > +[fragment shader]
> 
> > > +void main()
> 
> > > +{
> 
> > > + gl_FragColor = gl_Color;
> 
> > > +}
> 
> > > +
> 
> > > +[test]
> 
> > > +uniform int three 3
> 
> > > +uniform float five 5.0
> 
> > > +draw rect -1 -1 2 2
> 
> > > +probe all rgba 0.0 1.0 0.0 0.0
> 
> > > --
> 
> > > 1.7.7.6
> 
> > >
> 
> > > _______________________________________________
> 
> > > Piglit mailing list
> 
> > > Piglit at lists.freedesktop.org
> 
> > > http://lists.freedesktop.org/mailman/listinfo/piglit
> 
> > >
> 
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