radv/aco,nir/lower_subgroups: don't lower elect

ACO can implement this better.

fossil-db (Navi):
Totals from 33 (0.02% of 135946) affected shaders:
SGPRs: 1736 -> 1744 (+0.46%)
VGPRs: 1680 -> 1656 (-1.43%)
CodeSize: 246160 -> 245916 (-0.10%); split: -0.14%, +0.04%
MaxWaves: 449 -> 461 (+2.67%)
Instrs: 48301 -> 48266 (-0.07%); split: -0.12%, +0.05%
Cycles: 469740 -> 469240 (-0.11%); split: -0.18%, +0.08%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6558>

src/compiler/nir/nir.h

@@ -4440,6 +4440,7 @@ typedef struct nir_lower_subgroups_options {
    bool lower_quad:1;
    bool lower_quad_broadcast_dynamic:1;
    bool lower_quad_broadcast_dynamic_to_const:1;
+   bool lower_elect:1;
 } nir_lower_subgroups_options;
 
 bool nir_lower_subgroups(nir_shader *shader,

src/compiler/nir/nir_lower_subgroups.c

@@ -550,6 +550,9 @@ lower_subgroups_instr(nir_builder *b, nir_instr *instr, void *_options)
    }
 
    case nir_intrinsic_elect: {
+      if (!options->lower_elect)
+         return NULL;
+
       nir_intrinsic_instr *first =
          nir_intrinsic_instr_create(b->shader,
                                     nir_intrinsic_first_invocation);