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nir/loop_analyze: remove cost of redundant selects

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If we know that a select will be eliminated once the loop is
unrolled than we don't need to count the instruction towards the
cost of the loop.

This change helps 2 loops unroll in an xcom enemy unknown shader
that is loaded full of these redundant selects.

Acked-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18587>
This commit is contained in:
Timothy Arceri
2022-09-14 11:21:00 +10:00
committed by Marge Bot
parent 13d0ae593b
commit 40c32dfbb1
1 changed files with 33 additions and 2 deletions
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35
src/compiler/nir/nir_loop_analyze.c
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@@ -141,7 +141,8 @@ init_loop_def(nir_ssa_def *def, void *void_init_loop_state)
* unrolling doesn't cause things to blow up too much.
*/
static unsigned
instr_cost(nir_instr *instr, const nir_shader_compiler_options *options)
instr_cost(loop_info_state *state, nir_instr *instr,
const nir_shader_compiler_options *options)
{
if (instr->type == nir_instr_type_intrinsic ||
instr->type == nir_instr_type_tex)
@@ -154,6 +155,36 @@ instr_cost(nir_instr *instr, const nir_shader_compiler_options *options)
const nir_op_info *info = &nir_op_infos[alu->op];
unsigned cost = 1;
if (nir_op_is_selection(alu->op)) {
nir_ssa_scalar cond_scalar = {alu->src[0].src.ssa, 0};
if (nir_is_terminator_condition_with_two_inputs(cond_scalar)) {
nir_instr *sel_cond = alu->src[0].src.ssa->parent_instr;
nir_alu_instr *sel_alu = nir_instr_as_alu(sel_cond);
nir_ssa_scalar rhs, lhs;
lhs = nir_ssa_scalar_chase_alu_src(cond_scalar, 0);
rhs = nir_ssa_scalar_chase_alu_src(cond_scalar, 1);
/* If the selects condition is a comparision between a constant and
* a basic induction variable we know that it will be eliminated once
* the loop is unrolled so here we assign it a cost of 0.
*/
if ((nir_src_is_const(sel_alu->src[0].src) &&
get_loop_var(rhs.def, state)->type == basic_induction) ||
(nir_src_is_const(sel_alu->src[1].src) &&
get_loop_var(lhs.def, state)->type == basic_induction) ) {
/* Also if the selects condition is only used by the select then
* remove that alu instructons cost from the cost total also.
*/
if (!list_is_empty(&sel_alu->dest.dest.ssa.if_uses) ||
!list_is_singular(&sel_alu->dest.dest.ssa.uses))
return 0;
else
return -1;
}
}
}
if (alu->op == nir_op_flrp) {
if ((options->lower_flrp16 && nir_dest_bit_size(alu->dest.dest) == 16) ||
(options->lower_flrp32 && nir_dest_bit_size(alu->dest.dest) == 32) ||
@@ -1341,7 +1372,7 @@ get_loop_info(loop_info_state *state, nir_function_impl *impl)
nir_foreach_block_in_cf_node(block, &state->loop->cf_node) {
nir_foreach_instr(instr, block) {
state->loop->info->instr_cost += instr_cost(instr, options);
state->loop->info->instr_cost += instr_cost(state, instr, options);
}
if (state->loop->info->force_unroll)