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pan/mdg: Optimize liveness computation in DCE

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Rather than recompute liveness every block, compute it just once for the
whole shader, which ends up more efficient.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5123>
This commit is contained in:
Alyssa Rosenzweig 2020-05-06 17:34:09 -04:00 • committed by Marge Bot
parent c24dfc9da4
commit fc06b8b7dc
3 changed files with 25 additions and 7 deletions
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2
src/panfrost/midgard/compiler.h
View file

@ -649,7 +649,7 @@ void midgard_nir_lod_errata(nir_shader *shader);
bool midgard_opt_copy_prop(compiler_context *ctx, midgard_block *block);
bool midgard_opt_combine_projection(compiler_context *ctx, midgard_block *block);
bool midgard_opt_varying_projection(compiler_context *ctx, midgard_block *block);
bool midgard_opt_dead_code_eliminate(compiler_context *ctx, midgard_block *block);
bool midgard_opt_dead_code_eliminate(compiler_context *ctx);
bool midgard_opt_dead_move_eliminate(compiler_context *ctx, midgard_block *block);
bool midgard_opt_promote_fmov(compiler_context *ctx, midgard_block *block);

2
src/panfrost/midgard/midgard_compile.c
View file

@ -2622,11 +2622,11 @@ midgard_compile_shader_nir(nir_shader *nir, panfrost_program *program, bool is_b
do {
progress = false;
progress |= midgard_opt_dead_code_eliminate(ctx);
mir_foreach_block(ctx, _block) {
midgard_block *block = (midgard_block *) _block;
progress |= midgard_opt_copy_prop(ctx, block);
progress |= midgard_opt_dead_code_eliminate(ctx, block);
progress |= midgard_opt_combine_projection(ctx, block);
progress |= midgard_opt_varying_projection(ctx, block);
}

28
src/panfrost/midgard/midgard_opt_dce.c
View file

@ -63,14 +63,11 @@ can_dce(midgard_instruction *ins)
return true;
}
bool
midgard_opt_dead_code_eliminate(compiler_context *ctx, midgard_block *block)
static bool
midgard_opt_dead_code_eliminate_block(compiler_context *ctx, midgard_block *block)
{
bool progress = false;
mir_invalidate_liveness(ctx);
mir_compute_liveness(ctx);
uint16_t *live = mem_dup(block->base.live_out, ctx->temp_count * sizeof(uint16_t));
mir_foreach_instr_in_block_rev(block, ins) {
@ -100,6 +97,27 @@ midgard_opt_dead_code_eliminate(compiler_context *ctx, midgard_block *block)
return progress;
}
bool
midgard_opt_dead_code_eliminate(compiler_context *ctx)
{
/* We track liveness. In fact, it's ok if we assume more things are
* live than they actually are, that just reduces the effectiveness of
* this iterations lightly. And DCE has the effect of strictly reducing
* liveness, so we can run DCE across all blocks while only computing
* liveness at the beginning. */
mir_invalidate_liveness(ctx);
mir_compute_liveness(ctx);
bool progress = false;
mir_foreach_block(ctx, block) {
progress |= midgard_opt_dead_code_eliminate_block(ctx, (midgard_block *) block);
}
return progress;
}
/* Removes dead moves, that is, moves with a destination overwritten before
* being read. Normally handled implicitly as part of DCE, but this has to run
* after the out-of-SSA pass */