Mesa (master): nir: Remove handling of dead writes from copy_prop_vars
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Tue Oct 16 00:35:04 UTC 2018
Module: Mesa
Branch: master
Commit: 4dfa7adc100061f96e15fcbbfa5f776cd6c5a94a
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=4dfa7adc100061f96e15fcbbfa5f776cd6c5a94a
Author: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>
Date: Wed Aug 15 09:52:53 2018 -0700
nir: Remove handling of dead writes from copy_prop_vars
These are covered by another pass now.
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
---
src/compiler/nir/nir_opt_copy_prop_vars.c | 84 +++----------------------------
1 file changed, 8 insertions(+), 76 deletions(-)
diff --git a/src/compiler/nir/nir_opt_copy_prop_vars.c b/src/compiler/nir/nir_opt_copy_prop_vars.c
index 9fecaf0eee..5276aa176d 100644
--- a/src/compiler/nir/nir_opt_copy_prop_vars.c
+++ b/src/compiler/nir/nir_opt_copy_prop_vars.c
@@ -38,10 +38,7 @@
* 1) Copy-propagation on variables that have indirect access. This includes
* propagating from indirect stores into indirect loads.
*
- * 2) Dead code elimination of store_var and copy_var intrinsics based on
- * killed destination values.
- *
- * 3) Removal of redundant load_deref intrinsics. We can't trust regular CSE
+ * 2) Removal of redundant load_deref intrinsics. We can't trust regular CSE
* to do this because it isn't aware of variable writes that may alias the
* value and make the former load invalid.
*
@@ -51,6 +48,8 @@
* rapidly get out of hand. Fortunately, for anything that is only ever
* accessed directly, we get SSA based copy-propagation which is extremely
* powerful so this isn't that great a loss.
+ *
+ * Removal of dead writes to variables is handled by another pass.
*/
struct value {
@@ -64,9 +63,6 @@ struct value {
struct copy_entry {
struct list_head link;
- nir_instr *store_instr[4];
-
- unsigned comps_may_be_read;
struct value src;
nir_deref_instr *dst;
@@ -114,44 +110,6 @@ copy_entry_remove(struct copy_prop_var_state *state, struct copy_entry *entry)
list_add(&entry->link, &state->copy_free_list);
}
-static void
-remove_dead_writes(struct copy_prop_var_state *state,
- struct copy_entry *entry, unsigned write_mask)
-{
- /* We're overwriting another entry. Some of it's components may not
- * have been read yet and, if that's the case, we may be able to delete
- * some instructions but we have to be careful.
- */
- unsigned dead_comps = write_mask & ~entry->comps_may_be_read;
-
- for (unsigned mask = dead_comps; mask;) {
- unsigned i = u_bit_scan(&mask);
-
- nir_instr *instr = entry->store_instr[i];
-
- /* We may have already deleted it on a previous iteration */
- if (!instr)
- continue;
-
- /* See if this instr is used anywhere that it's not dead */
- bool keep = false;
- for (unsigned j = 0; j < 4; j++) {
- if (entry->store_instr[j] == instr) {
- if (dead_comps & (1 << j)) {
- entry->store_instr[j] = NULL;
- } else {
- keep = true;
- }
- }
- }
-
- if (!keep) {
- nir_instr_remove(instr);
- state->progress = true;
- }
- }
-}
-
static struct copy_entry *
lookup_entry_for_deref(struct copy_prop_var_state *state,
nir_deref_instr *deref,
@@ -165,16 +123,6 @@ lookup_entry_for_deref(struct copy_prop_var_state *state,
return NULL;
}
-static void
-mark_aliased_entries_as_read(struct copy_prop_var_state *state,
- nir_deref_instr *deref, unsigned components)
-{
- list_for_each_entry(struct copy_entry, iter, &state->copies, link) {
- if (nir_compare_derefs(iter->dst, deref) & nir_derefs_may_alias_bit)
- iter->comps_may_be_read |= components;
- }
-}
-
static struct copy_entry *
get_entry_and_kill_aliases(struct copy_prop_var_state *state,
nir_deref_instr *deref,
@@ -191,11 +139,6 @@ get_entry_and_kill_aliases(struct copy_prop_var_state *state,
}
nir_deref_compare_result comp = nir_compare_derefs(iter->dst, deref);
- /* This is a store operation. If we completely overwrite some value, we
- * want to delete any dead writes that may be present.
- */
- if (comp & nir_derefs_b_contains_a_bit)
- remove_dead_writes(state, iter, write_mask);
if (comp & nir_derefs_equal_bit) {
assert(entry == NULL);
@@ -228,25 +171,19 @@ apply_barrier_for_modes(struct copy_prop_var_state *state,
static void
store_to_entry(struct copy_prop_var_state *state, struct copy_entry *entry,
- const struct value *value, unsigned write_mask,
- nir_instr *store_instr)
+ const struct value *value, unsigned write_mask)
{
- entry->comps_may_be_read &= ~write_mask;
if (value->is_ssa) {
entry->src.is_ssa = true;
/* Only overwrite the written components */
for (unsigned i = 0; i < 4; i++) {
- if (write_mask & (1 << i)) {
- entry->store_instr[i] = store_instr;
+ if (write_mask & (1 << i))
entry->src.ssa[i] = value->ssa[i];
- }
}
} else {
/* Non-ssa stores always write everything */
entry->src.is_ssa = false;
entry->src.deref = value->deref;
- for (unsigned i = 0; i < 4; i++)
- entry->store_instr[i] = store_instr;
}
}
@@ -490,9 +427,6 @@ copy_prop_vars_block(struct copy_prop_var_state *state,
case nir_intrinsic_load_deref: {
nir_deref_instr *src = nir_src_as_deref(intrin->src[0]);
- uint8_t comps_read = nir_ssa_def_components_read(&intrin->dest.ssa);
- mark_aliased_entries_as_read(state, src, comps_read);
-
struct copy_entry *src_entry =
lookup_entry_for_deref(state, src, nir_derefs_a_contains_b_bit);
struct value value;
@@ -549,7 +483,7 @@ copy_prop_vars_block(struct copy_prop_var_state *state,
* subsequent store.
*/
store_to_entry(state, store_entry, &value,
- ((1 << intrin->num_components) - 1), NULL);
+ ((1 << intrin->num_components) - 1));
break;
}
@@ -565,7 +499,7 @@ copy_prop_vars_block(struct copy_prop_var_state *state,
unsigned wrmask = nir_intrinsic_write_mask(intrin);
struct copy_entry *entry =
get_entry_and_kill_aliases(state, dst, wrmask);
- store_to_entry(state, entry, &value, wrmask, &intrin->instr);
+ store_to_entry(state, entry, &value, wrmask);
break;
}
@@ -579,8 +513,6 @@ copy_prop_vars_block(struct copy_prop_var_state *state,
continue;
}
- mark_aliased_entries_as_read(state, src, 0xf);
-
struct copy_entry *src_entry =
lookup_entry_for_deref(state, src, nir_derefs_a_contains_b_bit);
struct value value;
@@ -610,7 +542,7 @@ copy_prop_vars_block(struct copy_prop_var_state *state,
struct copy_entry *dst_entry =
get_entry_and_kill_aliases(state, dst, 0xf);
- store_to_entry(state, dst_entry, &value, 0xf, &intrin->instr);
+ store_to_entry(state, dst_entry, &value, 0xf);
break;
}
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