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nir/opt_remove_phis: optimize out phis with undef

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This removes some phis that loop unrolling can create.

fossil-db (Navi):
Totals from 349 (0.26% of 135946) affected shaders:
SpillSGPRs: 52 -> 41 (-21.15%)
CodeSize: 3179968 -> 3169920 (-0.32%); split: -0.33%, +0.01%
Instrs: 626965 -> 624712 (-0.36%); split: -0.37%, +0.01%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6348>
This commit is contained in:
Rhys Perry
2020-08-17 12:18:24 +01:00
committed by Marge Bot
parent 326eb56718
commit 60dae98456
1 changed files with 6 additions and 1 deletions
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7
src/compiler/nir/nir_opt_remove_phis.c
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@@ -52,7 +52,7 @@ matching_mov(nir_alu_instr *mov1, nir_ssa_def *ssa)
* This is a pass for removing phi nodes that look like: * This is a pass for removing phi nodes that look like:
* a = phi(b, b, b, ...) * a = phi(b, b, b, ...)
* *
* Note that we can't ignore undef sources here, or else we may create a * Note that we can't always ignore undef sources here, or else we may create a
* situation where the definition of b isn't dominated by its uses. We're * situation where the definition of b isn't dominated by its uses. We're
* allowed to do this since the definition of b must dominate all of the * allowed to do this since the definition of b must dominate all of the
* phi node's predecessors, which means it must dominate the phi node as well * phi node's predecessors, which means it must dominate the phi node as well
@@ -98,6 +98,9 @@ remove_phis_block(nir_block *block, nir_builder *b)
if (def == NULL) { if (def == NULL) {
def = src->src.ssa; def = src->src.ssa;
mov = get_parent_mov(def); mov = get_parent_mov(def);
} else if (src->src.ssa->parent_instr->type == nir_instr_type_ssa_undef &&
nir_block_dominates(def->parent_instr->block, src->pred)) {
/* Ignore this undef source. */
} else { } else {
if (src->src.ssa != def && !matching_mov(mov, src->src.ssa)) { if (src->src.ssa != def && !matching_mov(mov, src->src.ssa)) {
srcs_same = false; srcs_same = false;
@@ -153,6 +156,8 @@ nir_opt_remove_phis_impl(nir_function_impl *impl)
nir_builder bld; nir_builder bld;
nir_builder_init(&bld, impl); nir_builder_init(&bld, impl);
nir_metadata_require(impl, nir_metadata_dominance);
nir_foreach_block(block, impl) { nir_foreach_block(block, impl) {
progress |= remove_phis_block(block, &bld); progress |= remove_phis_block(block, &bld);
} }