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

[Paul Berry]

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
> >
> > _______________________________________________
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> > Piglit at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/piglit
> >
>
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