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nir: don't try to optimize exclusive min/max scan to inclusive

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SPIR-V rules for fmax/fmin scans are *very* stupid.
The required identity is Inf instead of NaN but if one input
is NaN, the other value has to be returned.
This means for invocation 0:
min(subgroupExclusiveMin(NaN), NaN) -> Inf
subgroupInclusiveMin(NaN) -> undefined (NaN for any sane backend)

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27536>
This commit is contained in:
Georg Lehmann
2024-02-08 21:22:32 +01:00
committed by Marge Bot
parent df63f188e8
commit b44f97a7ba
1 changed files with 15 additions and 2 deletions
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src/compiler/nir/nir_opt_intrinsics.c
+15 -2
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@@ -258,8 +258,21 @@ try_opt_exclusive_scan_to_inclusive(nir_intrinsic_instr *intrin)
return false;
/* Don't reassociate exact float operations. */
if (nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type) == nir_type_float &&
alu->op != nir_op_fmax && alu->op != nir_op_fmin && alu->exact)
if (nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type) == nir_type_float && alu->exact)
return false;
/* SPIR-V rules for fmax/fmin scans are *very* stupid.
* The required identity is Inf instead of NaN but if one input
* is NaN, the other value has to be returned.
*
* This means for invocation 0:
* min(subgroupExclusiveMin(NaN), NaN) -> Inf
* subgroupInclusiveMin(NaN) -> undefined (NaN for any sane backend)
*
* SPIR-V [NF]Min/Max don't allow undefined result, even with standard
* float controls.
*/
if (alu->op == nir_op_fmax || alu->op == nir_op_fmin)
return false;
if (alu->def.num_components != 1)