Revert "panfrost: Rework midgard_pair_load_store() to kill the nested foreach loop"

There's a missing prev_ldst = NULL; assignment in the new logic,
but even with this fixed it seems to regress some applications,
so let's revert the change until we find the real problem.

This reverts commit c9bebae2877e55cdcd94f9f9f3f6805238caeb28.

1 files changed, 34 insertions, 29 deletions

diff --git a/src/panfrost/midgard/midgard_schedule.c b/src/panfrost/midgard/midgard_schedule.c
index feb988a66ba..b8d9b5ec9be 100644
--- a/src/panfrost/midgard/midgard_schedule.c
+++ b/src/panfrost/midgard/midgard_schedule.c
@@ -657,41 +657,46 @@ schedule_block(compiler_context *ctx, midgard_block *block)
 static void
 midgard_pair_load_store(compiler_context *ctx, midgard_block *block)
 {
-        midgard_instruction *prev_ldst = NULL;
-        int search_distance;
-
         mir_foreach_instr_in_block_safe(block, ins) {
-                if (ins->type != TAG_LOAD_STORE_4 && !prev_ldst) continue;
+                if (ins->type != TAG_LOAD_STORE_4) continue;
 
-                /* We've found a load/store op. Start searching for another one.
-                 * Maximum search distance to pair, to avoid register pressure disasters
-                 */
-                if (!prev_ldst) {
-                        search_distance = 8;
-                        prev_ldst = ins;
-                        continue;
-                }
+                /* We've found a load/store op. Check if next is also load/store. */
+                midgard_instruction *next_op = mir_next_op(ins);
+                if (&next_op->link != &block->instructions) {
+                        if (next_op->type == TAG_LOAD_STORE_4) {
+                                /* If so, we're done since we're a pair */
+                                ins = mir_next_op(ins);
+                                continue;
+                        }
 
-                /* Already paired. */
-                if (mir_prev_op(ins) == prev_ldst) {
-                        prev_ldst = NULL;
-                        continue;
-                }
+                        /* Maximum search distance to pair, to avoid register pressure disasters */
+                        int search_distance = 8;
 
-                /* We can only reorder if there are no sources */
-                bool deps = false;
-                for (unsigned s = 0; s < ARRAY_SIZE(ins->src); ++s)
-                        deps |= (ins->src[s] != ~0);
+                        /* Otherwise, we have an orphaned load/store -- search for another load */
+                        mir_foreach_instr_in_block_from(block, c, mir_next_op(ins)) {
+                                /* Terminate search if necessary */
+                                if (!(search_distance--)) break;
 
-                /* We found one! Move it up to pair */
-                if (!deps) {
-                        list_del(&ins->link);
-                        list_add(&ins->link, &prev_ldst->link);
-                        continue;
-                }
+                                if (c->type != TAG_LOAD_STORE_4) continue;
+
+                                /* We can only reorder if there are no sources */
+
+                                bool deps = false;
+
+                                for (unsigned s = 0; s < ARRAY_SIZE(ins->src); ++s)
+                                        deps |= (c->src[s] != ~0);
+
+                                if (deps)
+                                        continue;
 
-                if (!(search_distance--))
-                        prev_ldst = NULL;
+                                /* We found one! Move it up to pair and remove it from the old location */
+
+                                mir_insert_instruction_before(ctx, ins, *c);
+                                mir_remove_instruction(c);
+
+                                break;
+                        }
+                }
         }
 }