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nir_opt_deref: ptr_as_array(deref_cast<T*>(x))[0] isn't the same as x[0] if the cast has alignment

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This breaks CLOn12's handling of CL CTS test_basic vector_creation for char3 (at least).
Removing this cast causes us to try to load from a deref with no alignment info.

Fixes: 99bb2a4d ("nir/opt_deref: Don't remove casts with alignment information")
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10165>
(cherry picked from commit 4b69ae8e1e)
This commit is contained in:
Jesse Natalie 2021-04-11 19:15:35 -07:00 • committed by Dylan Baker
parent c30215de7e
commit 1e4bcfea0c
2 changed files with 4 additions and 2 deletions
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2
.pick_status.json
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@ -625,7 +625,7 @@
"description": "nir_opt_deref: ptr_as_array(deref_cast<T*>(x))[0] isn't the same as x[0] if the cast has alignment",
"nominated": true,
"nomination_type": 1,
"resolution": 0,
"resolution": 1,
"master_sha": null,
"because_sha": "99bb2a4de66fa662fb4bcb29df8e2749972ee986"
},

4
src/compiler/nir/nir_deref.c
View file

@ -1111,7 +1111,8 @@ opt_deref_ptr_as_array(nir_builder *b, nir_deref_instr *deref)
if (nir_src_is_const(deref->arr.index) &&
nir_src_as_int(deref->arr.index) == 0) {
/* If it's a ptr_as_array deref with an index of 0, it does nothing
* and we can just replace its uses with its parent.
* and we can just replace its uses with its parent, unless it has
* alignment information.
*
* The source of a ptr_as_array deref always has a deref_type of
* nir_deref_type_array or nir_deref_type_cast. If it's a cast, it
@ -1120,6 +1121,7 @@ opt_deref_ptr_as_array(nir_builder *b, nir_deref_instr *deref)
* opt_deref_cast() above.
*/
if (parent->deref_type == nir_deref_type_cast &&
parent->cast.align_mul == 0 &&
is_trivial_deref_cast(parent))
parent = nir_deref_instr_parent(parent);
nir_ssa_def_rewrite_uses(&deref->dest.ssa,