Mesa (staging/21.3): gallivm: avoid division by zero when computing cube face

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Module: Mesa
Branch: staging/21.3
Commit: b032600a2b5e7ef8cfef6bf678012c93181e5c64
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b032600a2b5e7ef8cfef6bf678012c93181e5c64

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Fri Mar  4 10:59:12 2022 -0500

gallivm: avoid division by zero when computing cube face

this is illegal and produces NaNs which blow up the sample instr

cc: mesa-stable

fixes (llvmpipe and zink):
KHR-GL45.incomplete_texture_access.sampler
dEQP-GLES31.functional.program_uniform.by_pointer.render.array_in_struct.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_pointer.render.array_in_struct.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_pointer.render.array_in_struct.sampler2D_samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_pointer.render.basic.samplerCube_both
dEQP-GLES31.functional.program_uniform.by_pointer.render.basic.samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_pointer.render.basic.samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_pointer.render.basic_struct.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_pointer.render.basic_struct.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_pointer.render.nested_structs_arrays.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_pointer.render.nested_structs_arrays.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_pointer.render.nested_structs_arrays.sampler2D_samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_pointer.render.struct_in_array.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_pointer.render.struct_in_array.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_pointer.render.struct_in_array.sampler2D_samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_value.render.array_in_struct.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_value.render.array_in_struct.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_value.render.array_in_struct.sampler2D_samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_value.render.basic.samplerCube_both
dEQP-GLES31.functional.program_uniform.by_value.render.basic.samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_value.render.basic.samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_value.render.basic_struct.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_value.render.basic_struct.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_value.render.nested_structs_arrays.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_value.render.nested_structs_arrays.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_value.render.nested_structs_arrays.sampler2D_samplerCube_vertex
dEQP-GLES31.functional.program_uniform.by_value.render.struct_in_array.sampler2D_samplerCube_both
dEQP-GLES31.functional.program_uniform.by_value.render.struct_in_array.sampler2D_samplerCube_fragment
dEQP-GLES31.functional.program_uniform.by_value.render.struct_in_array.sampler2D_samplerCube_vertex

Reviewed-by: Roland Scheidegger <sroland at vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15246>
(cherry picked from commit c82dcdf598f7b78c4a0106a71e008b482cf8f70b)

---

 .pick_status.json                             | 2 +-
 src/gallium/auxiliary/gallivm/lp_bld_sample.c | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index 2b6a663a39f..cb7e7e8e7fc 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -4,7 +4,7 @@
         "description": "gallivm: avoid division by zero when computing cube face",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null
     },
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_sample.c b/src/gallium/auxiliary/gallivm/lp_bld_sample.c
index 0c9a41aeb26..19bd8463d44 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_sample.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_sample.c
@@ -1726,7 +1726,10 @@ lp_build_cube_imapos(struct lp_build_context *coord_bld, LLVMValueRef coord)
    /* ima = +0.5 / abs(coord); */
    LLVMValueRef posHalf = lp_build_const_vec(coord_bld->gallivm, coord_bld->type, 0.5);
    LLVMValueRef absCoord = lp_build_abs(coord_bld, coord);
-   LLVMValueRef ima = lp_build_div(coord_bld, posHalf, absCoord);
+   /* avoid div by zero */
+   LLVMValueRef sel = lp_build_cmp(coord_bld, PIPE_FUNC_GREATER, absCoord, coord_bld->zero);
+   LLVMValueRef div = lp_build_div(coord_bld, posHalf, absCoord);
+   LLVMValueRef ima = lp_build_select(coord_bld, sel, div, coord_bld->zero);
    return ima;
 }