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nir/dead_variables: Remove shader-local variables that are only written

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Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>
This commit is contained in:
Jason Ekstrand
2016-12-09 19:37:12 -08:00
parent 58fe5c57cd
commit 13a2f20740
1 changed files with 60 additions and 9 deletions
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69
src/compiler/nir/nir_remove_dead_variables.c
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@@ -31,9 +31,27 @@ static void
add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live)
{
unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
for (unsigned i = 0; i < num_vars; i++) {
nir_variable *var = instr->variables[i]->var;
_mesa_set_add(live, var);
switch (instr->intrinsic) {
case nir_intrinsic_copy_var:
_mesa_set_add(live, instr->variables[1]->var);
/* Fall through */
case nir_intrinsic_store_var: {
/* The first source in both copy_var and store_var is the destination.
* If the variable is a local that never escapes the shader, then we
* don't mark it as live for just a store.
*/
nir_variable_mode mode = instr->variables[0]->var->data.mode;
if (!(mode & (nir_var_local | nir_var_global | nir_var_shared)))
_mesa_set_add(live, instr->variables[0]->var);
break;
}
default:
for (unsigned i = 0; i < num_vars; i++) {
_mesa_set_add(live, instr->variables[i]->var);
}
break;
}
}
@@ -94,6 +112,31 @@ add_var_use_shader(nir_shader *shader, struct set *live)
}
}
static void
remove_dead_var_writes(nir_shader *shader, struct set *live)
{
nir_foreach_function(function, shader) {
if (!function->impl)
continue;
nir_foreach_block(block, function->impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if (intrin->intrinsic != nir_intrinsic_copy_var &&
intrin->intrinsic != nir_intrinsic_store_var)
continue;
/* Stores to dead variables need to be removed */
if (intrin->variables[0]->var->data.mode == 0)
nir_instr_remove(instr);
}
}
}
}
static bool
remove_dead_vars(struct exec_list *var_list, struct set *live)
{
@@ -102,8 +145,9 @@ remove_dead_vars(struct exec_list *var_list, struct set *live)
foreach_list_typed_safe(nir_variable, var, node, var_list) {
struct set_entry *entry = _mesa_set_search(live, var);
if (entry == NULL) {
/* Mark this variable as used by setting the mode to 0 */
var->data.mode = 0;
exec_node_remove(&var->node);
ralloc_free(var);
progress = true;
}
}
@@ -141,12 +185,19 @@ nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes)
if (modes & nir_var_local) {
nir_foreach_function(function, shader) {
if (function->impl) {
if (remove_dead_vars(&function->impl->locals, live)) {
nir_metadata_preserve(function->impl, nir_metadata_block_index |
nir_metadata_dominance |
nir_metadata_live_ssa_defs);
if (remove_dead_vars(&function->impl->locals, live))
progress = true;
}
}
}
}
if (progress) {
remove_dead_var_writes(shader, live);
nir_foreach_function(function, shader) {
if (function->impl) {
nir_metadata_preserve(function->impl, nir_metadata_block_index |
nir_metadata_dominance);
}
}
}