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ir3/array_to_ssa: skip remove_trivial_phi for non-array phis

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remove_trivial_phi() mostly does nothing for non-array phis, but it
rewrites sources if their definining instruction are trivial phis.

In the case of trivial phis in the loop continue block (for loops with
divergent non-trivial continues), we might need to keep those if they
write a shared register, because the source of the trivial phi will not be
reachable from the loop header phi.

In this example, the predecessors of the continue block should be block2,
but the physical predecessors are block2 and block3, requiring a phi in
the continue block which will then be lowered by ir3_lower_shared_phis.
loop {
   block1:
   a = phi 0, b
   if (divergent) {
      block2:
      b = a + 1
      continue;
   }
   block3:
   break;
}

Fixes RA validation error when compiling blackmythwukong/5645a84e669a6179
from radv_fossils.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Backport-to: 26.0
(cherry picked from commit 4f0fb5784f)

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40979>
This commit is contained in:
Rhys Perry 2026-03-17 14:32:37 +00:00 • committed by Eric Engestrom
parent 6a2704a520
commit 9b19409ac8
2 changed files with 6 additions and 3 deletions
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2
.pick_status.json
View file

@ -544,7 +544,7 @@
"description": "ir3/array_to_ssa: skip remove_trivial_phi for non-array phis",
"nominated": true,
"nomination_type": 4,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": null,
"notes": null

7
src/freedreno/ir3/ir3_array_to_ssa.c
View file

@ -236,10 +236,13 @@ ir3_array_to_ssa(struct ir3 *ir)
foreach_block (block, &ir->block_list) {
foreach_instr_safe (instr, &block->instr_list) {
if (instr->opc == OPC_META_PHI)
if (instr->opc == OPC_META_PHI) {
if (!(instr->dsts[0]->flags & IR3_REG_ARRAY))
continue;
remove_trivial_phi(instr);
else
} else {
break;
}
}
}