2 * Copyright © 2014 Intel Corporation
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
24 * Jason Ekstrand (jason@jlekstrand.net)
29 #include "nir_builder.h"
30 #include "nir_phi_builder.h"
35 struct deref_node
*parent
;
36 const struct glsl_type
*type
;
40 /* Only valid for things that end up in the direct list.
41 * Note that multiple nir_deref_vars may correspond to this node, but they
42 * will all be equivalent, so any is as good as the other.
45 struct exec_node direct_derefs_link
;
51 struct nir_phi_builder_value
*pb_value
;
53 struct deref_node
*wildcard
;
54 struct deref_node
*indirect
;
55 struct deref_node
*children
[0];
58 struct lower_variables_state
{
61 nir_function_impl
*impl
;
63 /* A hash table mapping variables to deref_node data */
64 struct hash_table
*deref_var_nodes
;
66 /* A hash table mapping fully-qualified direct dereferences, i.e.
67 * dereferences with no indirect or wildcard array dereferences, to
70 * At the moment, we only lower loads, stores, and copies that can be
71 * trivially lowered to loads and stores, i.e. copies with no indirects
72 * and no wildcards. If a part of a variable that is being loaded from
73 * and/or stored into is also involved in a copy operation with
74 * wildcards, then we lower that copy operation to loads and stores, but
75 * otherwise we leave copies with wildcards alone. Since the only derefs
76 * used in these loads, stores, and trivial copies are ones with no
77 * wildcards and no indirects, these are precisely the derefs that we
78 * can actually consider lowering.
80 struct exec_list direct_deref_nodes
;
82 /* Controls whether get_deref_node will add variables to the
83 * direct_deref_nodes table. This is turned on when we are initially
84 * scanning for load/store instructions. It is then turned off so we
85 * don't accidentally change the direct_deref_nodes table while we're
86 * iterating throug it.
88 bool add_to_direct_deref_nodes
;
90 struct nir_phi_builder
*phi_builder
;
93 static struct deref_node
*
94 deref_node_create(struct deref_node
*parent
,
95 const struct glsl_type
*type
, nir_shader
*shader
)
97 size_t size
= sizeof(struct deref_node
) +
98 glsl_get_length(type
) * sizeof(struct deref_node
*);
100 struct deref_node
*node
= rzalloc_size(shader
, size
);
102 node
->parent
= parent
;
104 exec_node_init(&node
->direct_derefs_link
);
109 /* Returns the deref node associated with the given variable. This will be
110 * the root of the tree representing all of the derefs of the given variable.
112 static struct deref_node
*
113 get_deref_node_for_var(nir_variable
*var
, struct lower_variables_state
*state
)
115 struct deref_node
*node
;
117 struct hash_entry
*var_entry
=
118 _mesa_hash_table_search(state
->deref_var_nodes
, var
);
121 return var_entry
->data
;
123 node
= deref_node_create(NULL
, var
->type
, state
->dead_ctx
);
124 _mesa_hash_table_insert(state
->deref_var_nodes
, var
, node
);
129 /* Gets the deref_node for the given deref chain and creates it if it
130 * doesn't yet exist. If the deref is fully-qualified and direct and
131 * state->add_to_direct_deref_nodes is true, it will be added to the hash
132 * table of of fully-qualified direct derefs.
134 static struct deref_node
*
135 get_deref_node(nir_deref_var
*deref
, struct lower_variables_state
*state
)
137 bool is_direct
= true;
139 /* Start at the base of the chain. */
140 struct deref_node
*node
= get_deref_node_for_var(deref
->var
, state
);
141 assert(deref
->deref
.type
== node
->type
);
143 for (nir_deref
*tail
= deref
->deref
.child
; tail
; tail
= tail
->child
) {
144 switch (tail
->deref_type
) {
145 case nir_deref_type_struct
: {
146 nir_deref_struct
*deref_struct
= nir_deref_as_struct(tail
);
148 assert(deref_struct
->index
< glsl_get_length(node
->type
));
150 if (node
->children
[deref_struct
->index
] == NULL
)
151 node
->children
[deref_struct
->index
] =
152 deref_node_create(node
, tail
->type
, state
->dead_ctx
);
154 node
= node
->children
[deref_struct
->index
];
158 case nir_deref_type_array
: {
159 nir_deref_array
*arr
= nir_deref_as_array(tail
);
161 switch (arr
->deref_array_type
) {
162 case nir_deref_array_type_direct
:
163 /* This is possible if a loop unrolls and generates an
164 * out-of-bounds offset. We need to handle this at least
165 * somewhat gracefully.
167 if (arr
->base_offset
>= glsl_get_length(node
->type
))
170 if (node
->children
[arr
->base_offset
] == NULL
)
171 node
->children
[arr
->base_offset
] =
172 deref_node_create(node
, tail
->type
, state
->dead_ctx
);
174 node
= node
->children
[arr
->base_offset
];
177 case nir_deref_array_type_indirect
:
178 if (node
->indirect
== NULL
)
179 node
->indirect
= deref_node_create(node
, tail
->type
,
182 node
= node
->indirect
;
186 case nir_deref_array_type_wildcard
:
187 if (node
->wildcard
== NULL
)
188 node
->wildcard
= deref_node_create(node
, tail
->type
,
191 node
= node
->wildcard
;
196 unreachable("Invalid array deref type");
201 unreachable("Invalid deref type");
207 /* Only insert if it isn't already in the list. */
208 if (is_direct
&& state
->add_to_direct_deref_nodes
&&
209 node
->direct_derefs_link
.next
== NULL
) {
211 assert(deref
->var
!= NULL
);
212 exec_list_push_tail(&state
->direct_deref_nodes
,
213 &node
->direct_derefs_link
);
219 /* \sa foreach_deref_node_match */
221 foreach_deref_node_worker(struct deref_node
*node
, nir_deref
*deref
,
222 bool (* cb
)(struct deref_node
*node
,
223 struct lower_variables_state
*state
),
224 struct lower_variables_state
*state
)
226 if (deref
->child
== NULL
) {
227 return cb(node
, state
);
229 switch (deref
->child
->deref_type
) {
230 case nir_deref_type_array
: {
231 nir_deref_array
*arr
= nir_deref_as_array(deref
->child
);
232 assert(arr
->deref_array_type
== nir_deref_array_type_direct
);
233 if (node
->children
[arr
->base_offset
] &&
234 !foreach_deref_node_worker(node
->children
[arr
->base_offset
],
235 deref
->child
, cb
, state
))
238 if (node
->wildcard
&&
239 !foreach_deref_node_worker(node
->wildcard
,
240 deref
->child
, cb
, state
))
246 case nir_deref_type_struct
: {
247 nir_deref_struct
*str
= nir_deref_as_struct(deref
->child
);
248 return foreach_deref_node_worker(node
->children
[str
->index
],
249 deref
->child
, cb
, state
);
253 unreachable("Invalid deref child type");
258 /* Walks over every "matching" deref_node and calls the callback. A node
259 * is considered to "match" if either refers to that deref or matches up t
260 * a wildcard. In other words, the following would match a[6].foo[3].bar:
267 * The given deref must be a full-length and fully qualified (no wildcards
268 * or indirects) deref chain.
271 foreach_deref_node_match(nir_deref_var
*deref
,
272 bool (* cb
)(struct deref_node
*node
,
273 struct lower_variables_state
*state
),
274 struct lower_variables_state
*state
)
276 nir_deref_var var_deref
= *deref
;
277 var_deref
.deref
.child
= NULL
;
278 struct deref_node
*node
= get_deref_node(&var_deref
, state
);
283 return foreach_deref_node_worker(node
, &deref
->deref
, cb
, state
);
286 /* \sa deref_may_be_aliased */
288 deref_may_be_aliased_node(struct deref_node
*node
, nir_deref
*deref
,
289 struct lower_variables_state
*state
)
291 if (deref
->child
== NULL
) {
294 switch (deref
->child
->deref_type
) {
295 case nir_deref_type_array
: {
296 nir_deref_array
*arr
= nir_deref_as_array(deref
->child
);
297 if (arr
->deref_array_type
== nir_deref_array_type_indirect
)
300 /* If there is an indirect at this level, we're aliased. */
304 assert(arr
->deref_array_type
== nir_deref_array_type_direct
);
306 if (node
->children
[arr
->base_offset
] &&
307 deref_may_be_aliased_node(node
->children
[arr
->base_offset
],
308 deref
->child
, state
))
311 if (node
->wildcard
&&
312 deref_may_be_aliased_node(node
->wildcard
, deref
->child
, state
))
318 case nir_deref_type_struct
: {
319 nir_deref_struct
*str
= nir_deref_as_struct(deref
->child
);
320 if (node
->children
[str
->index
]) {
321 return deref_may_be_aliased_node(node
->children
[str
->index
],
322 deref
->child
, state
);
329 unreachable("Invalid nir_deref child type");
334 /* Returns true if there are no indirects that can ever touch this deref.
336 * For example, if the given deref is a[6].foo, then any uses of a[i].foo
337 * would cause this to return false, but a[i].bar would not affect it
338 * because it's a different structure member. A var_copy involving of
339 * a[*].bar also doesn't affect it because that can be lowered to entirely
340 * direct load/stores.
342 * We only support asking this question about fully-qualified derefs.
343 * Obviously, it's pointless to ask this about indirects, but we also
344 * rule-out wildcards. Handling Wildcard dereferences would involve
345 * checking each array index to make sure that there aren't any indirect
349 deref_may_be_aliased(nir_deref_var
*deref
,
350 struct lower_variables_state
*state
)
352 return deref_may_be_aliased_node(get_deref_node_for_var(deref
->var
, state
),
353 &deref
->deref
, state
);
357 register_load_instr(nir_intrinsic_instr
*load_instr
,
358 struct lower_variables_state
*state
)
360 struct deref_node
*node
= get_deref_node(load_instr
->variables
[0], state
);
364 if (node
->loads
== NULL
)
365 node
->loads
= _mesa_set_create(state
->dead_ctx
, _mesa_hash_pointer
,
366 _mesa_key_pointer_equal
);
368 _mesa_set_add(node
->loads
, load_instr
);
372 register_store_instr(nir_intrinsic_instr
*store_instr
,
373 struct lower_variables_state
*state
)
375 struct deref_node
*node
= get_deref_node(store_instr
->variables
[0], state
);
379 if (node
->stores
== NULL
)
380 node
->stores
= _mesa_set_create(state
->dead_ctx
, _mesa_hash_pointer
,
381 _mesa_key_pointer_equal
);
383 _mesa_set_add(node
->stores
, store_instr
);
387 register_copy_instr(nir_intrinsic_instr
*copy_instr
,
388 struct lower_variables_state
*state
)
390 for (unsigned idx
= 0; idx
< 2; idx
++) {
391 struct deref_node
*node
=
392 get_deref_node(copy_instr
->variables
[idx
], state
);
397 if (node
->copies
== NULL
)
398 node
->copies
= _mesa_set_create(state
->dead_ctx
, _mesa_hash_pointer
,
399 _mesa_key_pointer_equal
);
401 _mesa_set_add(node
->copies
, copy_instr
);
405 /* Registers all variable uses in the given block. */
407 register_variable_uses_block(nir_block
*block
, void *void_state
)
409 struct lower_variables_state
*state
= void_state
;
411 nir_foreach_instr_safe(block
, instr
) {
412 if (instr
->type
!= nir_instr_type_intrinsic
)
415 nir_intrinsic_instr
*intrin
= nir_instr_as_intrinsic(instr
);
417 switch (intrin
->intrinsic
) {
418 case nir_intrinsic_load_var
:
419 register_load_instr(intrin
, state
);
422 case nir_intrinsic_store_var
:
423 register_store_instr(intrin
, state
);
426 case nir_intrinsic_copy_var
:
427 register_copy_instr(intrin
, state
);
438 /* Walks over all of the copy instructions to or from the given deref_node
439 * and lowers them to load/store intrinsics.
442 lower_copies_to_load_store(struct deref_node
*node
,
443 struct lower_variables_state
*state
)
448 struct set_entry
*copy_entry
;
449 set_foreach(node
->copies
, copy_entry
) {
450 nir_intrinsic_instr
*copy
= (void *)copy_entry
->key
;
452 nir_lower_var_copy_instr(copy
, state
->shader
);
454 for (unsigned i
= 0; i
< 2; ++i
) {
455 struct deref_node
*arg_node
=
456 get_deref_node(copy
->variables
[i
], state
);
458 /* Only bother removing copy entries for other nodes */
459 if (arg_node
== NULL
|| arg_node
== node
)
462 struct set_entry
*arg_entry
= _mesa_set_search(arg_node
->copies
, copy
);
464 _mesa_set_remove(node
->copies
, arg_entry
);
467 nir_instr_remove(©
->instr
);
475 /* Performs variable renaming by doing a DFS of the dominance tree
477 * This algorithm is very similar to the one outlined in "Efficiently
478 * Computing Static Single Assignment Form and the Control Dependence
479 * Graph" by Cytron et. al. The primary difference is that we only put one
480 * SSA def on the stack per block.
483 rename_variables_block(nir_block
*block
, struct lower_variables_state
*state
)
486 nir_builder_init(&b
, state
->impl
);
488 nir_foreach_instr_safe(block
, instr
) {
489 if (instr
->type
!= nir_instr_type_intrinsic
)
492 nir_intrinsic_instr
*intrin
= nir_instr_as_intrinsic(instr
);
494 switch (intrin
->intrinsic
) {
495 case nir_intrinsic_load_var
: {
496 struct deref_node
*node
=
497 get_deref_node(intrin
->variables
[0], state
);
500 /* If we hit this path then we are referencing an invalid
501 * value. Most likely, we unrolled something and are
502 * reading past the end of some array. In any case, this
503 * should result in an undefined value.
505 nir_ssa_undef_instr
*undef
=
506 nir_ssa_undef_instr_create(state
->shader
,
507 intrin
->num_components
);
509 nir_instr_insert_before(&intrin
->instr
, &undef
->instr
);
510 nir_instr_remove(&intrin
->instr
);
512 nir_ssa_def_rewrite_uses(&intrin
->dest
.ssa
,
513 nir_src_for_ssa(&undef
->def
));
517 if (!node
->lower_to_ssa
)
520 nir_alu_instr
*mov
= nir_alu_instr_create(state
->shader
,
522 mov
->src
[0].src
= nir_src_for_ssa(
523 nir_phi_builder_value_get_block_def(node
->pb_value
, block
));
524 for (unsigned i
= intrin
->num_components
; i
< 4; i
++)
525 mov
->src
[0].swizzle
[i
] = 0;
527 assert(intrin
->dest
.is_ssa
);
529 mov
->dest
.write_mask
= (1 << intrin
->num_components
) - 1;
530 nir_ssa_dest_init(&mov
->instr
, &mov
->dest
.dest
,
531 intrin
->num_components
, NULL
);
533 nir_instr_insert_before(&intrin
->instr
, &mov
->instr
);
534 nir_instr_remove(&intrin
->instr
);
536 nir_ssa_def_rewrite_uses(&intrin
->dest
.ssa
,
537 nir_src_for_ssa(&mov
->dest
.dest
.ssa
));
541 case nir_intrinsic_store_var
: {
542 struct deref_node
*node
=
543 get_deref_node(intrin
->variables
[0], state
);
546 /* Probably an out-of-bounds array store. That should be a
548 nir_instr_remove(&intrin
->instr
);
552 if (!node
->lower_to_ssa
)
555 assert(intrin
->num_components
==
556 glsl_get_vector_elements(node
->type
));
558 assert(intrin
->src
[0].is_ssa
);
560 nir_ssa_def
*new_def
;
561 b
.cursor
= nir_before_instr(&intrin
->instr
);
563 unsigned wrmask
= nir_intrinsic_write_mask(intrin
);
564 if (wrmask
== (1 << intrin
->num_components
) - 1) {
565 /* Whole variable store - just copy the source. Note that
566 * intrin->num_components and intrin->src[0].ssa->num_components
570 for (unsigned i
= 0; i
< 4; i
++)
571 swiz
[i
] = i
< intrin
->num_components
? i
: 0;
573 new_def
= nir_swizzle(&b
, intrin
->src
[0].ssa
, swiz
,
574 intrin
->num_components
, false);
576 nir_ssa_def
*old_def
=
577 nir_phi_builder_value_get_block_def(node
->pb_value
, block
);
578 /* For writemasked store_var intrinsics, we combine the newly
579 * written values with the existing contents of unwritten
580 * channels, creating a new SSA value for the whole vector.
582 nir_ssa_def
*srcs
[4];
583 for (unsigned i
= 0; i
< intrin
->num_components
; i
++) {
584 if (wrmask
& (1 << i
)) {
585 srcs
[i
] = nir_channel(&b
, intrin
->src
[0].ssa
, i
);
587 srcs
[i
] = nir_channel(&b
, old_def
, i
);
590 new_def
= nir_vec(&b
, srcs
, intrin
->num_components
);
593 assert(new_def
->num_components
== intrin
->num_components
);
595 nir_phi_builder_value_set_block_def(node
->pb_value
, block
, new_def
);
596 nir_instr_remove(&intrin
->instr
);
605 for (unsigned i
= 0; i
< block
->num_dom_children
; ++i
)
606 rename_variables_block(block
->dom_children
[i
], state
);
611 /** Implements a pass to lower variable uses to SSA values
613 * This path walks the list of instructions and tries to lower as many
614 * local variable load/store operations to SSA defs and uses as it can.
615 * The process involves four passes:
617 * 1) Iterate over all of the instructions and mark where each local
618 * variable deref is used in a load, store, or copy. While we're at
619 * it, we keep track of all of the fully-qualified (no wildcards) and
620 * fully-direct references we see and store them in the
621 * direct_deref_nodes hash table.
623 * 2) Walk over the the list of fully-qualified direct derefs generated in
624 * the previous pass. For each deref, we determine if it can ever be
625 * aliased, i.e. if there is an indirect reference anywhere that may
626 * refer to it. If it cannot be aliased, we mark it for lowering to an
627 * SSA value. At this point, we lower any var_copy instructions that
628 * use the given deref to load/store operations and, if the deref has a
629 * constant initializer, we go ahead and add a load_const value at the
630 * beginning of the function with the initialized value.
632 * 3) Walk over the list of derefs we plan to lower to SSA values and
633 * insert phi nodes as needed.
635 * 4) Perform "variable renaming" by replacing the load/store instructions
636 * with SSA definitions and SSA uses.
639 nir_lower_vars_to_ssa_impl(nir_function_impl
*impl
)
641 struct lower_variables_state state
;
643 state
.shader
= impl
->function
->shader
;
644 state
.dead_ctx
= ralloc_context(state
.shader
);
647 state
.deref_var_nodes
= _mesa_hash_table_create(state
.dead_ctx
,
649 _mesa_key_pointer_equal
);
650 exec_list_make_empty(&state
.direct_deref_nodes
);
652 /* Build the initial deref structures and direct_deref_nodes table */
653 state
.add_to_direct_deref_nodes
= true;
654 nir_foreach_block(impl
, register_variable_uses_block
, &state
);
656 bool progress
= false;
658 nir_metadata_require(impl
, nir_metadata_block_index
);
660 /* We're about to iterate through direct_deref_nodes. Don't modify it. */
661 state
.add_to_direct_deref_nodes
= false;
663 foreach_list_typed_safe(struct deref_node
, node
, direct_derefs_link
,
664 &state
.direct_deref_nodes
) {
665 nir_deref_var
*deref
= node
->deref
;
667 if (deref
->var
->data
.mode
!= nir_var_local
) {
668 exec_node_remove(&node
->direct_derefs_link
);
672 if (deref_may_be_aliased(deref
, &state
)) {
673 exec_node_remove(&node
->direct_derefs_link
);
677 node
->lower_to_ssa
= true;
680 foreach_deref_node_match(deref
, lower_copies_to_load_store
, &state
);
686 nir_metadata_require(impl
, nir_metadata_dominance
);
688 /* We may have lowered some copy instructions to load/store
689 * instructions. The uses from the copy instructions hav already been
690 * removed but we need to rescan to ensure that the uses from the newly
691 * added load/store instructions are registered. We need this
692 * information for phi node insertion below.
694 nir_foreach_block(impl
, register_variable_uses_block
, &state
);
696 state
.phi_builder
= nir_phi_builder_create(state
.impl
);
698 NIR_VLA(BITSET_WORD
, store_blocks
, BITSET_WORDS(state
.impl
->num_blocks
));
699 foreach_list_typed(struct deref_node
, node
, direct_derefs_link
,
700 &state
.direct_deref_nodes
) {
701 if (!node
->lower_to_ssa
)
704 memset(store_blocks
, 0,
705 BITSET_WORDS(state
.impl
->num_blocks
) * sizeof(*store_blocks
));
708 struct set_entry
*store_entry
;
709 set_foreach(node
->stores
, store_entry
) {
710 nir_intrinsic_instr
*store
=
711 (nir_intrinsic_instr
*)store_entry
->key
;
712 BITSET_SET(store_blocks
, store
->instr
.block
->index
);
716 if (node
->deref
->var
->constant_initializer
)
717 BITSET_SET(store_blocks
, 0);
720 nir_phi_builder_add_value(state
.phi_builder
,
721 glsl_get_vector_elements(node
->type
),
724 if (node
->deref
->var
->constant_initializer
) {
725 nir_load_const_instr
*load
=
726 nir_deref_get_const_initializer_load(state
.shader
, node
->deref
);
727 nir_instr_insert_before_cf_list(&impl
->body
, &load
->instr
);
728 nir_phi_builder_value_set_block_def(node
->pb_value
,
729 nir_start_block(impl
), &load
->def
);
733 rename_variables_block(nir_start_block(impl
), &state
);
735 nir_phi_builder_finish(state
.phi_builder
);
737 nir_metadata_preserve(impl
, nir_metadata_block_index
|
738 nir_metadata_dominance
);
740 ralloc_free(state
.dead_ctx
);
746 nir_lower_vars_to_ssa(nir_shader
*shader
)
748 nir_foreach_function(shader
, function
) {
750 nir_lower_vars_to_ssa_impl(function
->impl
);