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ir_constant: Return zero on out-of-bounds vector accesses

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Several optimization paths, including constant folding, can lead to
accessing an ir_constant vector with an out of bounds index.

Return 0 since GL_ARB_robustness and GL_KHR_robustness encourage
us to do so.

Fixes piglit tests:
spec@glsl-1.20@execution@vector-out-of-bounds-access@fs-vec4-out-of-bounds-2
spec@glsl-1.20@execution@vector-out-of-bounds-access@fs-vec4-out-of-bounds-4
spec@glsl-1.20@execution@vector-out-of-bounds-access@fs-vec4-out-of-bounds-5

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2604
CC: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6363>
(cherry picked from commit e93979ba59)
This commit is contained in:
Danylo Piliaiev 2020-08-17 18:13:24 +03:00 • committed by Eric Engestrom
parent 6273688e65
commit 1d9aa0e99a
2 changed files with 15 additions and 1 deletions
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2
.pick_status.json
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@ -3937,7 +3937,7 @@
"description": "ir_constant: Return zero on out-of-bounds vector accesses",
"nominated": true,
"nomination_type": 0,
"resolution": 0,
"resolution": 1,
"master_sha": null,
"because_sha": null
},

14
src/compiler/glsl/ir.cpp
View file

@ -799,6 +799,20 @@ ir_constant::ir_constant(const ir_constant *c, unsigned i)
this->const_elements = NULL;
this->type = c->type->get_base_type();
/* Section 5.11 (Out-of-Bounds Accesses) of the GLSL 4.60 spec says:
*
* In the subsections described above for array, vector, matrix and
* structure accesses, any out-of-bounds access produced undefined
* behavior....Out-of-bounds reads return undefined values, which
* include values from other variables of the active program or zero.
*
* GL_KHR_robustness and GL_ARB_robustness encourage us to return zero.
*/
if (i >= c->type->vector_elements) {
this->value = { { 0 } };
return;
}
switch (this->type->base_type) {
case GLSL_TYPE_UINT: this->value.u[0] = c->value.u[i]; break;
case GLSL_TYPE_INT: this->value.i[0] = c->value.i[i]; break;