Jason, JFYI, I have been looking into the cases where the boolean
bitsize lowering pass was producing worse instruction counts that the
default 32-bit pass and I have tracked it down to this patch. Reverting
this makes the instruction count much better for some tests, I'll check
why this happens tomorrow.
Iago
On Mon, 2018-10-22 at 17:13 -0500, Jason Ekstrand wrote:
> Instead of doing our own constant folding, we just emit instructions
> and
> let constant folding happen. This is substantially simpler and lets
> us
> use the nir_imm_bool helper instead of dealing with the const_value's
> ourselves.
> ---
> src/compiler/nir/nir_opt_if.c | 91 ++++++++++++---------------------
> --
> 1 file changed, 30 insertions(+), 61 deletions(-)
>
> diff --git a/src/compiler/nir/nir_opt_if.c
> b/src/compiler/nir/nir_opt_if.c
> index 0c94aa170b5..60368a0259e 100644
> --- a/src/compiler/nir/nir_opt_if.c
> +++ b/src/compiler/nir/nir_opt_if.c
> @@ -377,31 +377,15 @@ opt_if_loop_terminator(nir_if *nif)
> return true;
> }
>
> -static void
> -replace_if_condition_use_with_const(nir_builder *b, nir_src *use,
> - nir_const_value nir_boolean,
> - bool if_condition)
> -{
> - /* Create const */
> - nir_ssa_def *const_def = nir_build_imm(b, 1, 32, nir_boolean);
> -
> - /* Rewrite use to use const */
> - nir_src new_src = nir_src_for_ssa(const_def);
> - if (if_condition)
> - nir_if_rewrite_condition(use->parent_if, new_src);
> - else
> - nir_instr_rewrite_src(use->parent_instr, use, new_src);
> -}
> -
> static bool
> -evaluate_if_condition(nir_if *nif, nir_cursor cursor, uint32_t
> *value)
> +evaluate_if_condition(nir_if *nif, nir_cursor cursor, bool *value)
> {
> nir_block *use_block = nir_cursor_current_block(cursor);
> if (nir_block_dominates(nir_if_first_then_block(nif), use_block))
> {
> - *value = NIR_TRUE;
> + *value = true;
> return true;
> } else if (nir_block_dominates(nir_if_first_else_block(nif),
> use_block)) {
> - *value = NIR_FALSE;
> + *value = false;
> return true;
> } else {
> return false;
> @@ -460,52 +444,31 @@ propagate_condition_eval(nir_builder *b, nir_if
> *nif, nir_src *use_src,
> nir_src *alu_use, nir_alu_instr *alu,
> bool is_if_condition)
> {
> - bool progress = false;
> + bool bool_value;
> + if (!evaluate_if_condition(nif, b->cursor, &bool_value))
> + return false;
>
> - nir_const_value bool_value;
> b->cursor = nir_before_src(alu_use, is_if_condition);
> - if (nir_op_infos[alu->op].num_inputs == 1) {
> - assert(alu->op == nir_op_inot || alu->op == nir_op_b2i);
> -
> - if (evaluate_if_condition(nif, b->cursor, &bool_value.u32[0]))
> {
> - assert(nir_src_bit_size(alu->src[0].src) == 32);
> -
> - nir_const_value result =
> - nir_eval_const_opcode(alu->op, 1, 32, &bool_value);
>
> - replace_if_condition_use_with_const(b, alu_use, result,
> - is_if_condition);
> - progress = true;
> + nir_ssa_def *def[2] = { };
> + for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
> + if (alu->src[i].src.ssa == use_src->ssa) {
> + def[i] = nir_imm_bool(b, bool_value);
> + } else {
> + def[i] = alu->src[i].src.ssa;
> }
> - } else {
> - assert(alu->op == nir_op_ior || alu->op == nir_op_iand);
> -
> - if (evaluate_if_condition(nif, b->cursor, &bool_value.u32[0]))
> {
> - nir_ssa_def *def[2];
> - for (unsigned i = 0; i < 2; i++) {
> - if (alu->src[i].src.ssa == use_src->ssa) {
> - def[i] = nir_build_imm(b, 1, 32, bool_value);
> - } else {
> - def[i] = alu->src[i].src.ssa;
> - }
> - }
> -
> - nir_ssa_def *nalu =
> - nir_build_alu(b, alu->op, def[0], def[1], NULL, NULL);
> -
> - /* Rewrite use to use new alu instruction */
> - nir_src new_src = nir_src_for_ssa(nalu);
> + }
> + nir_ssa_def *nalu = nir_build_alu(b, alu->op, def[0], def[1],
> NULL, NULL);
>
> - if (is_if_condition)
> - nir_if_rewrite_condition(alu_use->parent_if, new_src);
> - else
> - nir_instr_rewrite_src(alu_use->parent_instr, alu_use,
> new_src);
> + /* Rewrite use to use new alu instruction */
> + nir_src new_src = nir_src_for_ssa(nalu);
>
> - progress = true;
> - }
> - }
> + if (is_if_condition)
> + nir_if_rewrite_condition(alu_use->parent_if, new_src);
> + else
> + nir_instr_rewrite_src(alu_use->parent_instr, alu_use,
> new_src);
>
> - return progress;
> + return true;
> }
>
> static bool
> @@ -527,11 +490,17 @@ evaluate_condition_use(nir_builder *b, nir_if
> *nif, nir_src *use_src,
> {
> bool progress = false;
>
> - nir_const_value value;
> b->cursor = nir_before_src(use_src, is_if_condition);
>
> - if (evaluate_if_condition(nif, b->cursor, &value.u32[0])) {
> - replace_if_condition_use_with_const(b, use_src, value,
> is_if_condition);
> + bool bool_value;
> + if (evaluate_if_condition(nif, b->cursor, &bool_value)) {
> + /* Rewrite use to use const */
> + nir_src imm_src = nir_src_for_ssa(nir_imm_bool(b,
> bool_value));
> + if (is_if_condition)
> + nir_if_rewrite_condition(use_src->parent_if, imm_src);
> + else
> + nir_instr_rewrite_src(use_src->parent_instr, use_src,
> imm_src);
> +
> progress = true;
> }
>
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