On Mon, Jul 23, 2018 at 3:02 AM Timothy Arceri <tarc...@itsqueeze.com>
wrote:
> This adds support for unrolling the classic
>
> do {
> // ...
> } while (false)
>
> that is used to wrap multi-line macros. GLSL IR also wraps switch
> statements in a loop like this.
>
> shader-db results IVB:
>
> total loops in shared programs: 2515 -> 2512 (-0.12%)
> loops in affected programs: 33 -> 30 (-9.09%)
> helped: 3
> HURT: 0
> ---
> src/compiler/nir/nir_opt_loop_unroll.c | 77 ++++++++++++++++++++++++++
> 1 file changed, 77 insertions(+)
>
> diff --git a/src/compiler/nir/nir_opt_loop_unroll.c
> b/src/compiler/nir/nir_opt_loop_unroll.c
> index e0e0b754716..9c33267cb72 100644
> --- a/src/compiler/nir/nir_opt_loop_unroll.c
> +++ b/src/compiler/nir/nir_opt_loop_unroll.c
> @@ -465,6 +465,65 @@ complex_unroll(nir_loop *loop, nir_loop_terminator
> *unlimit_term,
> _mesa_hash_table_destroy(remap_table, NULL);
> }
>
> +/* Unrolls the classic wrapper loops e.g
> + *
> + * do {
> + * // ...
> + * } while (false)
> + */
> +static bool
> +wrapper_unroll(nir_loop *loop)
> +{
> + bool progress = false;
> +
> + nir_block *blk_after_loop =
> + nir_cursor_current_block(nir_after_cf_node(&loop->cf_node));
> +
> + /* There may still be some single src phis following the loop that
> + * have not yet been cleaned up by another pass. Tidy those up before
> + * unrolling the loop.
> + */
> + nir_foreach_instr_safe(instr, blk_after_loop) {
> + if (instr->type != nir_instr_type_phi)
> + break;
> +
> + nir_phi_instr *phi = nir_instr_as_phi(instr);
> + assert(exec_list_length(&phi->srcs) == 1);
> +
> + nir_phi_src *phi_src = exec_node_data(nir_phi_src,
> +
> exec_list_get_head(&phi->srcs),
> + node);
> +
> + nir_ssa_def_rewrite_uses(&phi->dest.ssa, phi_src->src);
> + nir_instr_remove(instr);
> +
> + progress = true;
> + }
> +
> + nir_block *last_loop_blk = nir_loop_last_block(loop);
> + if (nir_block_ends_in_break(last_loop_blk)) {
> +
> + /* Remove break at end of the loop */
> + nir_instr *break_instr = nir_block_last_instr(last_loop_blk);
> + nir_instr_remove(break_instr);
> +
> + /* Pluck out the loop body. */
> + nir_cf_list loop_body;
> + nir_cf_extract(&loop_body,
> nir_before_block(nir_loop_first_block(loop)),
> + nir_after_block(nir_loop_last_block(loop)));
> +
> + /* Reinsert loop body after the loop */
> + nir_cf_reinsert(&loop_body, nir_after_cf_node(&loop->cf_node));
> +
> + /* The loop has been unrolled so remove it. */
> + nir_cf_node_remove(&loop->cf_node);
> +
> + progress = true;
> + }
> +
> + return progress;
> +}
> +
> static bool
> is_loop_small_enough_to_unroll(nir_shader *shader, nir_loop_info *li)
> {
> @@ -516,6 +575,24 @@ process_loops(nir_shader *sh, nir_cf_node *cf_node,
> bool *has_nested_loop_out)
> */
> if (!progress) {
>
> + /* Check for the classic
> + *
> + * do {
> + * // ...
> + * } while (false)
> + *
> + * that is used to wrap multi-line macros. GLSL IR also wraps switch
> + * statements in a loop like this.
> + */
> + if (loop->info->limiting_terminator == NULL &&
> + list_empty(&loop->info->loop_terminator_list) &&
> + !loop->info->complex_loop) {
>
What does this do with "do { } while (true)"? Would those also hit this
path? If they do, unrolling them is probably ok since it's a GPU hang if
we don't but I thought it was worth asking.
> +
> + progress = wrapper_unroll(loop);
> +
> + goto exit;
> + }
> +
> if (has_nested_loop || loop->info->limiting_terminator == NULL)
> goto exit;
>
> --
> 2.17.1
>
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