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pan/midgard: Implement load/store pairing

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We can bundle two load/store together. This eliminates the need for
explicit load/store pairing in a prepass, as well.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
This commit is contained in:
Alyssa Rosenzweig 2019-09-23 15:57:58 -04:00
parent 7cf4932410
commit 8462e82467
1 changed files with 12 additions and 55 deletions
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67
src/panfrost/midgard/midgard_schedule.c
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@ -1141,17 +1141,26 @@ mir_schedule_ldst(
.exclude = ~0
};
/* Try to pick two load/store ops. Second not gauranteed to exist */
midgard_instruction *ins =
mir_choose_instruction(instructions, worklist, len, &predicate);
mir_update_worklist(worklist, len, instructions, ins);
midgard_instruction *pair =
mir_choose_instruction(instructions, worklist, len, &predicate);
struct midgard_bundle out = {
.tag = TAG_LOAD_STORE_4,
.instruction_count = 1,
.instructions = { ins }
.instruction_count = pair ? 2 : 1,
.instructions = { ins, pair }
};
/* We have to update the worklist atomically, since the two
* instructions run concurrently (TODO: verify it's not pipelined) */
mir_update_worklist(worklist, len, instructions, ins);
mir_update_worklist(worklist, len, instructions, pair);
return out;
}
@ -1341,54 +1350,6 @@ schedule_block(compiler_context *ctx, midgard_block *block)
ctx->quadword_count += block->quadword_count;
}
/* The following passes reorder MIR instructions to enable better scheduling */
static void
midgard_pair_load_store(compiler_context *ctx, midgard_block *block)
{
mir_foreach_instr_in_block_safe(block, ins) {
if (ins->type != TAG_LOAD_STORE_4) 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;
}
/* Maximum search distance to pair, to avoid register pressure disasters */
int search_distance = 8;
/* 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;
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;
/* 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;
}
}
}
}
/* When we're 'squeezing down' the values in the IR, we maintain a hash
* as such */
@ -1665,10 +1626,6 @@ schedule_program(compiler_context *ctx)
midgard_promote_uniforms(ctx, 16);
mir_foreach_block(ctx, block) {
midgard_pair_load_store(ctx, block);
}
/* Must be lowered right before RA */
mir_squeeze_index(ctx);
mir_lower_special_reads(ctx);