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nir/opt_remove_phis: rematerialize constants

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Foz-DB Navi31:
Totals from 749 (0.94% of 79395) affected shaders:
Instrs: 1224359 -> 1223722 (-0.05%); split: -0.07%, +0.02%
CodeSize: 6468392 -> 6466296 (-0.03%); split: -0.06%, +0.03%
Latency: 9764410 -> 9766457 (+0.02%); split: -0.01%, +0.03%
InvThroughput: 1017401 -> 1017380 (-0.00%); split: -0.03%, +0.03%
VClause: 19902 -> 19873 (-0.15%); split: -0.16%, +0.02%
SClause: 38441 -> 38424 (-0.04%); split: -0.05%, +0.01%
Copies: 86880 -> 86304 (-0.66%); split: -0.73%, +0.06%
Branches: 34206 -> 34159 (-0.14%); split: -0.14%, +0.01%
PreSGPRs: 45557 -> 45527 (-0.07%); split: -0.08%, +0.01%
PreVGPRs: 32406 -> 32408 (+0.01%)
VALU: 671633 -> 671533 (-0.01%); split: -0.02%, +0.01%
SALU: 155284 -> 154675 (-0.39%); split: -0.40%, +0.00%
VMEM: 27303 -> 27271 (-0.12%)
SMEM: 67490 -> 67455 (-0.05%)

Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31031>
This commit is contained in:
Georg Lehmann 2024-09-04 18:33:59 +02:00 • committed by Marge Bot
parent 40fc85c15b
commit 60776f87c3
1 changed files with 56 additions and 35 deletions
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91
src/compiler/nir/nir_opt_remove_phis.c
View file

@ -28,24 +28,48 @@
#include "nir.h"
#include "nir_builder.h"
static nir_alu_instr *
get_parent_mov(nir_def *ssa)
static bool
phi_srcs_equal(nir_def *a, nir_def *b)
{
if (ssa->parent_instr->type != nir_instr_type_alu)
return NULL;
if (a == b)
return true;
nir_alu_instr *alu = nir_instr_as_alu(ssa->parent_instr);
return (alu->op == nir_op_mov) ? alu : NULL;
if (a->parent_instr->type != b->parent_instr->type)
return false;
if (a->parent_instr->type != nir_instr_type_alu &&
a->parent_instr->type != nir_instr_type_load_const)
return false;
if (!nir_instrs_equal(a->parent_instr, b->parent_instr))
return false;
/* nir_instrs_equal ignores exact/fast_math */
if (a->parent_instr->type == nir_instr_type_alu) {
nir_alu_instr *a_alu = nir_instr_as_alu(a->parent_instr);
nir_alu_instr *b_alu = nir_instr_as_alu(b->parent_instr);
if (a_alu->exact != b_alu->exact || a_alu->fp_fast_math != b_alu->fp_fast_math)
return false;
}
return true;
}
static bool
matching_mov(nir_alu_instr *mov1, nir_def *ssa)
can_rematerialize_phi_src(nir_block *block, nir_def *def)
{
if (!mov1)
return false;
nir_alu_instr *mov2 = get_parent_mov(ssa);
return mov2 && nir_alu_srcs_equal(mov1, mov2, 0, 0);
if (def->parent_instr->type == nir_instr_type_alu) {
/* Restrict alu to movs. */
nir_alu_instr *alu = nir_instr_as_alu(def->parent_instr);
if (alu->op != nir_op_mov)
return false;
if (!nir_block_dominates(alu->src[0].src.ssa->parent_instr->block, block->imm_dom))
return false;
return true;
} else if (def->parent_instr->type == nir_instr_type_load_const) {
return true;
}
return false;
}
/*
@ -70,8 +94,8 @@ remove_phis_block(nir_block *block, nir_builder *b)
nir_foreach_phi_safe(phi, block) {
nir_def *def = NULL;
nir_alu_instr *mov = NULL;
bool srcs_same = true;
bool needs_remat = false;
nir_foreach_phi_src(src, phi) {
/* For phi nodes at the beginning of loops, we may encounter some
@ -88,17 +112,22 @@ remove_phis_block(nir_block *block, nir_builder *b)
if (src->src.ssa == &phi->def)
continue;
/* Ignore undef sources. */
if (nir_src_is_undef(src->src))
continue;
if (def == NULL) {
def = src->src.ssa;
mov = get_parent_mov(def);
} else if (nir_src_is_undef(src->src) &&
nir_block_dominates(def->parent_instr->block, src->pred)) {
/* Ignore this undef source. */
} else {
if (src->src.ssa != def && !matching_mov(mov, src->src.ssa)) {
srcs_same = false;
break;
if (!nir_block_dominates(def->parent_instr->block, block->imm_dom)) {
if (!can_rematerialize_phi_src(block, def)) {
srcs_same = false;
break;
}
needs_remat = true;
}
} else if (!phi_srcs_equal(src->src.ssa, def)) {
srcs_same = false;
break;
}
}
@ -106,22 +135,14 @@ remove_phis_block(nir_block *block, nir_builder *b)
continue;
if (!def) {
/* In this case, the phi had no sources. So turn it into an undef. */
/* In this case, the phi had no non undef sources. So turn it into an undef. */
b->cursor = nir_after_phis(block);
def = nir_undef(b, phi->def.num_components,
phi->def.bit_size);
} else if (mov) {
/* If the sources were all movs from the same source with the same
* swizzle, then we can't just pick a random move because it may not
* dominate the phi node. Instead, we need to emit our own move after
* the phi which uses the shared source, and rewrite uses of the phi
* to use the move instead. This is ok, because while the movs may
* not all dominate the phi node, their shared source does.
*/
def = nir_undef(b, phi->def.num_components, phi->def.bit_size);
} else if (needs_remat) {
b->cursor = nir_after_phis(block);
def = nir_mov_alu(b, mov->src[0], def->num_components);
nir_instr *remat = nir_instr_clone(b->shader, def->parent_instr);
nir_builder_instr_insert(b, remat);
def = nir_instr_def(remat);
}
nir_def_replace(&phi->def, def);