nir: get rid of OOB dereferences in nir_lower_io_arrays_to_elements
This patch fixes mesa compiler crash in i965 on shaders like the following one:
```
in VS_OUTPUT {
mat4 data;
} vs_output;
out vec4 fs_output;
vec4 convert(in float val) {
return vec4(val);
}
void main()
{
fs_output = vec4(0.0);
for (int a = -1; a < 5; a++) {
for (int b = -1; b < 5; b++) {
fs_output += convert(vs_output.data[b][a]);
}
}
}
```
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.
Out-of-bounds writes may be discarded or overwrite
other variables of the active program.
GL_KHR_robustness and GL_ARB_robustness encourage us to return zero
for reads.
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Signed-off-by: Andrii Simiklit <andrii.simiklit@globallogic.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6560>
1 file changed
