pan/bi: Cull DTSEL_IMM dests in post-RA DCE

They are useless (given the semantics of DTSEL_IMM) and complicate
scoreboarding. Just remove them in the pass that removes all the other silly
register destinations.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14298>

diff --git a/src/panfrost/bifrost/bi_opt_dce.c b/src/panfrost/bifrost/bi_opt_dce.c
index 141591d..d1d3592 100644 (file)
--- a/src/panfrost/bifrost/bi_opt_dce.c
+++ b/src/panfrost/bifrost/bi_opt_dce.c
@@ -160,6 +160,9 @@ bi_opt_dce_post_ra(bi_context *ctx)
                 uint64_t live = block->reg_live_out;
 
                 bi_foreach_instr_in_block_rev(block, ins) {
+                        if (ins->op == BI_OPCODE_DTSEL_IMM)
+                                ins->dest[0] = bi_null();
+
                         bi_foreach_dest(ins, d) {
                                 if (ins->dest[d].type != BI_INDEX_REGISTER)
                                         continue;