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nir/copy_prop: visit copies instead of sources

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There are less copy instructions than sources, so instead of visiting each
source and rewriting it if it's uses a copy instruction, visit each copy
instruction and rewrite it's users.

Besides improving compile time, this also has a side effect of fixing a
rare situation where copy-propagation does not happen:
loop {
   a = phi ..., b
   c = vec ...
   b = mov c.y
}
It might have been the case that a phi source could not be rewritten until
the copy was visited later.

Compile-time (nir_copy_prop):
Difference at 95.0% confidence
	-2613.13 +/- 15.2094
	-27.4333% +/- 0.150247%
	(Student's t, pooled s = 17.963)

Comple-time (overall):
Difference at 95.0% confidence
	-2627.89 +/- 201.557
	-2.05404% +/- 0.156221%
	(Student's t, pooled s = 238.048)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8784>
This commit is contained in:
Rhys Perry
2021-01-29 17:29:32 +00:00
committed by Marge Bot
parent 41125bff4f
commit c2209d836c
1 changed files with 121 additions and 213 deletions
Download Patch File Download Diff File Expand all files Collapse all files

334
src/compiler/nir/nir_opt_copy_propagate.c
View File

@@ -26,249 +26,162 @@
*/
#include "nir.h"
#include "nir_builder.h"
/**
* SSA-based copy propagation
*/
static bool is_move(nir_alu_instr *instr)
{
assert(instr->src[0].src.is_ssa);
if (instr->op != nir_op_mov)
return false;
if (instr->dest.saturate)
return false;
/* we handle modifiers in a separate pass */
if (instr->src[0].abs || instr->src[0].negate)
return false;
return true;
}
static bool is_vec(nir_alu_instr *instr)
{
for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
assert(instr->src[i].src.is_ssa);
/* we handle modifiers in a separate pass */
if (instr->src[i].abs || instr->src[i].negate)
return false;
}
assert(instr->dest.dest.is_ssa);
return nir_op_is_vec(instr->op);
}
static bool
is_swizzleless_move(nir_alu_instr *instr)
{
if (is_move(instr)) {
for (unsigned i = 0; i < NIR_MAX_VEC_COMPONENTS; i++) {
if (!((instr->dest.write_mask >> i) & 1))
break;
unsigned num_comp = instr->dest.dest.ssa.num_components;
if (instr->src[0].src.ssa->num_components != num_comp)
return false;
if (instr->op == nir_op_mov) {
for (unsigned i = 0; i < num_comp; i++) {
if (instr->src[0].swizzle[i] != i)
return false;
}
return true;
} else if (is_vec(instr)) {
nir_ssa_def *def = NULL;
for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
if (instr->src[i].swizzle[0] != i)
} else {
for (unsigned i = 0; i < num_comp; i++) {
if (instr->src[i].swizzle[0] != i ||
instr->src[i].src.ssa != instr->src[0].src.ssa)
return false;
if (def == NULL) {
def = instr->src[i].src.ssa;
} else if (instr->src[i].src.ssa != def) {
return false;
}
}
return true;
} else {
return false;
}
}
static bool
copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if,
unsigned num_components)
{
assert(src->is_ssa);
nir_ssa_def *original_ssa = src->ssa;
nir_instr *src_instr = original_ssa->parent_instr;
nir_ssa_def *copy_def;
if (src_instr->type == nir_instr_type_alu) {
nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
if (!is_swizzleless_move(alu_instr))
return false;
if (alu_instr->src[0].src.ssa->num_components != num_components)
return false;
copy_def= alu_instr->src[0].src.ssa;
} else {
return false;
}
if (parent_instr) {
nir_instr_rewrite_src(parent_instr, src, nir_src_for_ssa(copy_def));
} else {
assert(src == &parent_if->condition);
nir_if_rewrite_condition(parent_if, nir_src_for_ssa(copy_def));
}
if (nir_ssa_def_is_unused(original_ssa))
nir_instr_remove(src_instr);
return true;
}
static bool
copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index)
is_copy(nir_alu_instr *instr)
{
nir_alu_src *src = &parent_alu_instr->src[index];
assert(src->src.is_ssa);
assert(instr->src[0].src.is_ssa);
nir_ssa_def *original_ssa = src->src.ssa;
nir_instr *src_instr = original_ssa->parent_instr;
if (src_instr->type != nir_instr_type_alu)
return false;
nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
if (!is_move(alu_instr) && !is_vec(alu_instr))
return false;
nir_ssa_def *def;
unsigned new_swizzle[NIR_MAX_VEC_COMPONENTS] = {0, 0, 0, 0};
if (alu_instr->op == nir_op_mov) {
for (unsigned i = 0; i < NIR_MAX_VEC_COMPONENTS; i++)
new_swizzle[i] = alu_instr->src[0].swizzle[src->swizzle[i]];
def = alu_instr->src[0].src.ssa;
} else {
def = NULL;
for (unsigned i = 0; i < NIR_MAX_VEC_COMPONENTS; i++) {
if (!nir_alu_instr_channel_used(parent_alu_instr, index, i))
continue;
nir_ssa_def *new_def = alu_instr->src[src->swizzle[i]].src.ssa;
if (def == NULL)
def = new_def;
else {
if (def != new_def)
return false;
}
new_swizzle[i] = alu_instr->src[src->swizzle[i]].swizzle[0];
/* we handle modifiers in a separate pass */
if (instr->op == nir_op_mov) {
return !instr->dest.saturate &&
!instr->src[0].abs &&
!instr->src[0].negate;
} else if (nir_op_is_vec(instr->op)) {
for (unsigned i = 0; i < instr->dest.dest.ssa.num_components; i++) {
if (instr->src[i].abs || instr->src[i].negate)
return false;
}
return !instr->dest.saturate;
} else {
return false;
}
}
for (unsigned i = 0; i < NIR_MAX_VEC_COMPONENTS; i++)
src->swizzle[i] = new_swizzle[i];
static bool
rewrite_to_vec(nir_function_impl *impl, nir_alu_instr *mov, nir_alu_instr *vec)
{
if (mov->op != nir_op_mov)
return false;
nir_instr_rewrite_src(&parent_alu_instr->instr, &src->src,
nir_src_for_ssa(def));
nir_builder b;
nir_builder_init(&b, impl);
b.cursor = nir_after_instr(&mov->instr);
if (nir_ssa_def_is_unused(original_ssa))
nir_instr_remove(src_instr);
unsigned num_comp = mov->dest.dest.ssa.num_components;
nir_alu_instr *new_vec = nir_alu_instr_create(b.shader, nir_op_vec(num_comp));
for (unsigned i = 0; i < num_comp; i++)
new_vec->src[i] = vec->src[mov->src[0].swizzle[i]];
nir_ssa_def *new = nir_builder_alu_instr_finish_and_insert(&b, new_vec);
nir_ssa_def_rewrite_uses_ssa(&mov->dest.dest.ssa, new);
/* If we remove "mov" and it's the next instruction in the
* nir_foreach_instr_safe() loop, then we would end copy-propagation early. */
return true;
}
static bool
copy_prop_instr(nir_instr *instr)
copy_propagate_alu(nir_function_impl *impl, nir_alu_src *src, nir_alu_instr *copy)
{
nir_ssa_def *def = NULL;
nir_alu_instr *user = nir_instr_as_alu(src->src.parent_instr);
unsigned src_idx = src - user->src;
assert(src_idx < nir_op_infos[user->op].num_inputs);
unsigned num_comp = nir_ssa_alu_instr_src_components(user, src_idx);
if (copy->op == nir_op_mov) {
def = copy->src[0].src.ssa;
for (unsigned i = 0; i < num_comp; i++)
src->swizzle[i] = copy->src[0].swizzle[src->swizzle[i]];
} else {
def = copy->src[src->swizzle[0]].src.ssa;
for (unsigned i = 1; i < num_comp; i++) {
if (copy->src[src->swizzle[i]].src.ssa != def)
return rewrite_to_vec(impl, user, copy);
}
for (unsigned i = 0; i < num_comp; i++)
src->swizzle[i] = copy->src[src->swizzle[i]].swizzle[0];
}
nir_instr_rewrite_src(&user->instr, &src->src, nir_src_for_ssa(def));
return true;
}
static bool
copy_propagate(nir_src *src, nir_alu_instr *copy)
{
if (!is_swizzleless_move(copy))
return false;
nir_instr_rewrite_src(src->parent_instr, src, nir_src_for_ssa(copy->src[0].src.ssa));
return true;
}
static bool
copy_propagate_if(nir_src *src, nir_alu_instr *copy)
{
if (!is_swizzleless_move(copy))
return false;
nir_if *parent_if = container_of(src, nir_if, condition);
nir_if_rewrite_condition(parent_if, nir_src_for_ssa(copy->src[0].src.ssa));
return true;
}
static bool
copy_prop_instr(nir_function_impl *impl, nir_instr *instr)
{
if (instr->type != nir_instr_type_alu)
return false;
nir_alu_instr *mov = nir_instr_as_alu(instr);
if (!is_copy(mov))
return false;
bool progress = false;
switch (instr->type) {
case nir_instr_type_alu: {
nir_alu_instr *alu_instr = nir_instr_as_alu(instr);
for (unsigned i = 0; i < nir_op_infos[alu_instr->op].num_inputs; i++)
while (copy_prop_alu_src(alu_instr, i))
progress = true;
return progress;
nir_foreach_use_safe(src, &mov->dest.dest.ssa) {
if (src->parent_instr->type == nir_instr_type_alu)
progress |= copy_propagate_alu(impl, container_of(src, nir_alu_src, src), mov);
else
progress |= copy_propagate(src, mov);
}
case nir_instr_type_deref: {
nir_deref_instr *deref = nir_instr_as_deref(instr);
nir_foreach_if_use_safe(src, &mov->dest.dest.ssa)
progress |= copy_propagate_if(src, mov);
if (deref->deref_type != nir_deref_type_var) {
assert(deref->dest.is_ssa);
const unsigned comps = deref->dest.ssa.num_components;
while (copy_prop_src(&deref->parent, instr, NULL, comps))
progress = true;
}
if (progress && nir_ssa_def_is_unused(&mov->dest.dest.ssa))
nir_instr_remove(&mov->instr);
if (deref->deref_type == nir_deref_type_array ||
deref->deref_type == nir_deref_type_ptr_as_array) {
while (copy_prop_src(&deref->arr.index, instr, NULL, 1))
progress = true;
}
return progress;
}
case nir_instr_type_tex: {
nir_tex_instr *tex = nir_instr_as_tex(instr);
for (unsigned i = 0; i < tex->num_srcs; i++) {
unsigned num_components = nir_tex_instr_src_size(tex, i);
while (copy_prop_src(&tex->src[i].src, instr, NULL, num_components))
progress = true;
}
return progress;
}
case nir_instr_type_intrinsic: {
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
for (unsigned i = 0;
i < nir_intrinsic_infos[intrin->intrinsic].num_srcs; i++) {
unsigned num_components = nir_intrinsic_src_components(intrin, i);
while (copy_prop_src(&intrin->src[i], instr, NULL, num_components))
progress = true;
}
return progress;
}
case nir_instr_type_jump: {
nir_jump_instr *jump = nir_instr_as_jump(instr);
if (jump->type == nir_jump_goto_if) {
while (copy_prop_src(&jump->condition, instr, NULL, 1))
progress = true;
}
return progress;
}
case nir_instr_type_phi: {
nir_phi_instr *phi = nir_instr_as_phi(instr);
assert(phi->dest.is_ssa);
unsigned num_components = phi->dest.ssa.num_components;
nir_foreach_phi_src(src, phi) {
while (copy_prop_src(&src->src, instr, NULL, num_components))
progress = true;
}
return progress;
}
default:
return false;
}
}
static bool
copy_prop_if(nir_if *if_stmt)
{
return copy_prop_src(&if_stmt->condition, NULL, if_stmt, 1);
return progress;
}
static bool
@@ -277,15 +190,10 @@ nir_copy_prop_impl(nir_function_impl *impl)
bool progress = false;
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
if (copy_prop_instr(instr))
progress = true;
}
nir_if *if_stmt = nir_block_get_following_if(block);
if (if_stmt && copy_prop_if(if_stmt))
progress = true;
nir_foreach_instr_safe(instr, block) {
progress |= copy_prop_instr(impl, instr);
}
}
if (progress) {
nir_metadata_preserve(impl, nir_metadata_block_index |