On 09/12/2018 09:17 PM, Ilia Mirkin wrote: > On Wed, Sep 12, 2018 at 7:59 PM, Ian Romanick <i...@freedesktop.org> wrote: >> On 09/12/2018 04:33 PM, Ilia Mirkin wrote: >>> On Wed, Sep 12, 2018 at 7:29 PM, Ian Romanick <i...@freedesktop.org> wrote: >>>> From: Ian Romanick <ian.d.roman...@intel.com> >>>> >>>> The optimizer recently added the ability to replace a compare with a >>>> subtraction under certain circumstances. This can fail for integers. >>>> For inputs a = 0x80000000, b = 4, int(0x80000000) < 4, but >>>> int(0x80000000) - 4 overflows and results in 0x7ffffffc. That's not >>>> less than zero, so the flags get set differently than for (a < b). >>>> >>>> This really only affected the signed comparisons because the subtract >>>> would always have a signed source types, so it wouldn't be seen as a >>>> match for the compare with unsigned source types. >>>> >>>> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com> >>>> Cc: Matt Turner <matts...@gmail.com> >>>> --- >>>> tests/spec/CMakeLists.txt | 1 + >>>> .../fs-absoluteDifference-int.shader_test | 85 >>>> +++++++++++++++++++ >>>> .../fs-absoluteDifference-uint.shader_test | 85 >>>> +++++++++++++++++++ >>>> .../vs-absoluteDifference-int.shader_test | 96 >>>> ++++++++++++++++++++++ >>>> .../vs-absoluteDifference-uint.shader_test | 96 >>>> ++++++++++++++++++++++ >>>> 5 files changed, 363 insertions(+) >>>> create mode 100644 >>>> tests/spec/glsl-1.30/execution/fs-absoluteDifference-int.shader_test >>>> create mode 100644 >>>> tests/spec/glsl-1.30/execution/fs-absoluteDifference-uint.shader_test >>>> create mode 100644 >>>> tests/spec/glsl-1.30/execution/vs-absoluteDifference-int.shader_test >>>> create mode 100644 >>>> tests/spec/glsl-1.30/execution/vs-absoluteDifference-uint.shader_test >>>> >>>> diff --git a/tests/spec/CMakeLists.txt b/tests/spec/CMakeLists.txt >>>> index 4df9d331d..28abf3634 100644 >>>> --- a/tests/spec/CMakeLists.txt >>>> +++ b/tests/spec/CMakeLists.txt >>>> @@ -2,6 +2,7 @@ add_subdirectory (amd_framebuffer_multisample_advanced) >>>> add_subdirectory (amd_depth_clamp_separate) >>>> add_subdirectory (amd_performance_monitor) >>>> add_subdirectory (amd_pinned_memory) >>>> +add_subdirectory (amd_transform_feedback3_lines_triangles) >>>> add_subdirectory (arb_arrays_of_arrays) >>>> add_subdirectory (arb_base_instance) >>>> add_subdirectory (arb_bindless_texture) >>>> diff --git >>>> a/tests/spec/glsl-1.30/execution/fs-absoluteDifference-int.shader_test >>>> b/tests/spec/glsl-1.30/execution/fs-absoluteDifference-int.shader_test >>>> new file mode 100644 >>>> index 000000000..cdac53cdf >>>> --- /dev/null >>>> +++ b/tests/spec/glsl-1.30/execution/fs-absoluteDifference-int.shader_test >>>> @@ -0,0 +1,85 @@ >>>> +[require] >>>> +GL >= 3.0 >>>> +GLSL >= 1.30 >>>> + >>>> +[vertex shader passthrough] >>>> + >>>> +[fragment shader] >>>> +#extension GL_EXT_shader_integer_mix: enable >>>> + >>>> +// { A, B, absoluteDifference(A, B) } >>>> +uniform ivec3 data[40]; >>>> + >>>> +out vec4 color; >>>> + >>>> +uint abs_diff(int a, int b) >>>> +{ >>>> + /* This can fail if the compiler replaces the (a < b) with the result >>>> of >>>> + * one of the subtractions. For inputs a = 0x80000000, b = 4, >>>> + * int(0x80000000) < 4, but int(0x80000000)-4 overflows and results in >>>> + * 0x7ffffffc. That's not less than zero, so the flags get set >>>> + * differently than for (a < b). >>>> + */ >>>> +#ifndef GL_EXT_shader_integer_mix >>>> + return (a < b) ? uint(b - a) : uint(a - b); >>>> +#else >>>> + return mix(uint(a - b), uint(b - a), a < b); >>>> +#endif >>> >>> Why bother with this? It'll end up testing different code depending on >>> the extensions that the driver supports, which seems like a really bad >>> idea. >> >> We only hit the bug in the mix() case because how how we lower flow >> control to bcsel. I thought about having it require >> GL_EXT_shader_integer_mix. That means that when a driver enabled that >> extension the test could transition SKIP->FAIL which seems more likely >> to be ignored than PASS->FAIL. I guess now there's a possible >> FAIL->PASS transition. Meh. >> >> I'm not married to it being either way. I just want to reproduce the >> bug that I added to the i965 driver a few months ago. :) > > Hmm. Meh indeed. I dunno though -- skip -> fail when enabling an ext > seems pretty bad to me. I'd just require EXT_shader_integer_mix. In > practice, it's enabled everywhere GL 3.0 is (in mesa), so it's all a > bit academic.
Fair enough. The bikeshedder in me has difficulty deciding where the tests should live. It requires extensions beyond GLSL 1.30, so spec/glsl-1.30 doesn't seem good. It's not really a GL_EXT_shader_integer_mix test, so spec/ext_shader_integer_mix doesn't seem good either. :) > -ilia _______________________________________________ Piglit mailing list Piglit@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/piglit