2 * Copyright © 2015 Thomas Helland
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
25 #include "nir_constant_expressions.h"
26 #include "nir_loop_analyze.h"
33 } nir_loop_variable_type
;
35 struct nir_basic_induction_var
;
38 /* A link for the work list */
39 struct list_head process_link
;
43 /* The ssa_def associated with this info */
46 /* The type of this ssa_def */
47 nir_loop_variable_type type
;
49 /* If this is of type basic_induction */
50 struct nir_basic_induction_var
*ind
;
52 /* True if variable is in an if branch */
55 /* True if variable is in a nested loop */
60 typedef struct nir_basic_induction_var
{
61 nir_op alu_op
; /* The type of alu-operation */
62 nir_loop_variable
*alu_def
; /* The def of the alu-operation */
63 nir_loop_variable
*invariant
; /* The invariant alu-operand */
64 nir_loop_variable
*def_outside_loop
; /* The phi-src outside the loop */
65 } nir_basic_induction_var
;
68 /* The loop we store information for */
71 /* Loop_variable for all ssa_defs in function */
72 nir_loop_variable
*loop_vars
;
74 /* A list of the loop_vars to analyze */
75 struct list_head process_list
;
77 nir_variable_mode indirect_mask
;
81 static nir_loop_variable
*
82 get_loop_var(nir_ssa_def
*value
, loop_info_state
*state
)
84 return &(state
->loop_vars
[value
->index
]);
88 loop_info_state
*state
;
94 init_loop_def(nir_ssa_def
*def
, void *void_init_loop_state
)
96 init_loop_state
*loop_init_state
= void_init_loop_state
;
97 nir_loop_variable
*var
= get_loop_var(def
, loop_init_state
->state
);
99 if (loop_init_state
->in_nested_loop
) {
100 var
->in_nested_loop
= true;
101 } else if (loop_init_state
->in_if_branch
) {
102 var
->in_if_branch
= true;
104 /* Add to the tail of the list. That way we start at the beginning of
105 * the defs in the loop instead of the end when walking the list. This
106 * means less recursive calls. Only add defs that are not in nested
107 * loops or conditional blocks.
109 list_addtail(&var
->process_link
, &loop_init_state
->state
->process_list
);
117 /** Calculate an estimated cost in number of instructions
119 * We do this so that we don't unroll loops which will later get massively
120 * inflated due to int64 or fp64 lowering. The estimates provided here don't
121 * have to be massively accurate; they just have to be good enough that loop
122 * unrolling doesn't cause things to blow up too much.
125 instr_cost(nir_instr
*instr
, const nir_shader_compiler_options
*options
)
127 if (instr
->type
== nir_instr_type_intrinsic
||
128 instr
->type
== nir_instr_type_tex
)
131 if (instr
->type
!= nir_instr_type_alu
)
134 nir_alu_instr
*alu
= nir_instr_as_alu(instr
);
135 const nir_op_info
*info
= &nir_op_infos
[alu
->op
];
137 /* Assume everything 16 or 32-bit is cheap.
139 * There are no 64-bit ops that don't have a 64-bit thing as their
140 * destination or first source.
142 if (nir_dest_bit_size(alu
->dest
.dest
) < 64 &&
143 nir_src_bit_size(alu
->src
[0].src
) < 64)
146 bool is_fp64
= nir_dest_bit_size(alu
->dest
.dest
) == 64 &&
147 nir_alu_type_get_base_type(info
->output_type
) == nir_type_float
;
148 for (unsigned i
= 0; i
< info
->num_inputs
; i
++) {
149 if (nir_src_bit_size(alu
->src
[i
].src
) == 64 &&
150 nir_alu_type_get_base_type(info
->input_types
[i
]) == nir_type_float
)
155 /* If it's something lowered normally, it's expensive. */
157 if (options
->lower_doubles_options
&
158 nir_lower_doubles_op_to_options_mask(alu
->op
))
161 /* If it's full software, it's even more expensive */
162 if (options
->lower_doubles_options
& nir_lower_fp64_full_software
)
167 if (options
->lower_int64_options
&
168 nir_lower_int64_op_to_options_mask(alu
->op
)) {
169 /* These require a doing the division algorithm. */
170 if (alu
->op
== nir_op_idiv
|| alu
->op
== nir_op_udiv
||
171 alu
->op
== nir_op_imod
|| alu
->op
== nir_op_umod
||
172 alu
->op
== nir_op_irem
)
175 /* Other int64 lowering isn't usually all that expensive */
184 init_loop_block(nir_block
*block
, loop_info_state
*state
,
185 bool in_if_branch
, bool in_nested_loop
,
186 const nir_shader_compiler_options
*options
)
188 init_loop_state init_state
= {.in_if_branch
= in_if_branch
,
189 .in_nested_loop
= in_nested_loop
,
192 nir_foreach_instr(instr
, block
) {
193 state
->loop
->info
->instr_cost
+= instr_cost(instr
, options
);
194 nir_foreach_ssa_def(instr
, init_loop_def
, &init_state
);
201 is_var_alu(nir_loop_variable
*var
)
203 return var
->def
->parent_instr
->type
== nir_instr_type_alu
;
207 is_var_constant(nir_loop_variable
*var
)
209 return var
->def
->parent_instr
->type
== nir_instr_type_load_const
;
213 is_var_phi(nir_loop_variable
*var
)
215 return var
->def
->parent_instr
->type
== nir_instr_type_phi
;
219 mark_invariant(nir_ssa_def
*def
, loop_info_state
*state
)
221 nir_loop_variable
*var
= get_loop_var(def
, state
);
223 if (var
->type
== invariant
)
227 var
->type
= invariant
;
231 if (var
->type
== not_invariant
)
234 if (is_var_alu(var
)) {
235 nir_alu_instr
*alu
= nir_instr_as_alu(def
->parent_instr
);
237 for (unsigned i
= 0; i
< nir_op_infos
[alu
->op
].num_inputs
; i
++) {
238 if (!mark_invariant(alu
->src
[i
].src
.ssa
, state
)) {
239 var
->type
= not_invariant
;
243 var
->type
= invariant
;
247 /* Phis shouldn't be invariant except if one operand is invariant, and the
248 * other is the phi itself. These should be removed by opt_remove_phis.
249 * load_consts are already set to invariant and constant during init,
250 * and so should return earlier. Remaining op_codes are set undefined.
252 var
->type
= not_invariant
;
257 compute_invariance_information(loop_info_state
*state
)
259 /* An expression is invariant in a loop L if:
262 * – it’s a variable use, all of whose single defs are outside of L
264 * – it’s a pure computation all of whose args are loop invariant
265 * – it’s a variable use whose single reaching def, and the
266 * rhs of that def is loop-invariant
268 list_for_each_entry_safe(nir_loop_variable
, var
, &state
->process_list
,
270 assert(!var
->in_if_branch
&& !var
->in_nested_loop
);
272 if (mark_invariant(var
->def
, state
))
273 list_del(&var
->process_link
);
277 /* If all of the instruction sources point to identical ALU instructions (as
278 * per nir_instrs_equal), return one of the ALU instructions. Otherwise,
281 static nir_alu_instr
*
282 phi_instr_as_alu(nir_phi_instr
*phi
)
284 nir_alu_instr
*first
= NULL
;
285 nir_foreach_phi_src(src
, phi
) {
286 assert(src
->src
.is_ssa
);
287 if (src
->src
.ssa
->parent_instr
->type
!= nir_instr_type_alu
)
290 nir_alu_instr
*alu
= nir_instr_as_alu(src
->src
.ssa
->parent_instr
);
294 if (!nir_instrs_equal(&first
->instr
, &alu
->instr
))
303 compute_induction_information(loop_info_state
*state
)
305 bool found_induction_var
= false;
306 list_for_each_entry_safe(nir_loop_variable
, var
, &state
->process_list
,
309 /* It can't be an induction variable if it is invariant. Invariants and
310 * things in nested loops or conditionals should have been removed from
311 * the list by compute_invariance_information().
313 assert(!var
->in_if_branch
&& !var
->in_nested_loop
&&
314 var
->type
!= invariant
);
316 /* We are only interested in checking phis for the basic induction
317 * variable case as its simple to detect. All basic induction variables
320 if (!is_var_phi(var
))
323 /* We only handle scalars because none of the rest of the loop analysis
324 * code can properly handle swizzles.
326 if (var
->def
->num_components
> 1)
329 nir_phi_instr
*phi
= nir_instr_as_phi(var
->def
->parent_instr
);
330 nir_basic_induction_var
*biv
= rzalloc(state
, nir_basic_induction_var
);
332 nir_foreach_phi_src(src
, phi
) {
333 nir_loop_variable
*src_var
= get_loop_var(src
->src
.ssa
, state
);
335 /* If one of the sources is in an if branch or nested loop then don't
336 * attempt to go any further.
338 if (src_var
->in_if_branch
|| src_var
->in_nested_loop
)
341 /* Detect inductions variables that are incremented in both branches
342 * of an unnested if rather than in a loop block.
344 if (is_var_phi(src_var
)) {
345 nir_phi_instr
*src_phi
=
346 nir_instr_as_phi(src_var
->def
->parent_instr
);
347 nir_alu_instr
*src_phi_alu
= phi_instr_as_alu(src_phi
);
349 src_var
= get_loop_var(&src_phi_alu
->dest
.dest
.ssa
, state
);
350 if (!src_var
->in_if_branch
)
355 if (!src_var
->in_loop
) {
356 biv
->def_outside_loop
= src_var
;
357 } else if (is_var_alu(src_var
)) {
358 nir_alu_instr
*alu
= nir_instr_as_alu(src_var
->def
->parent_instr
);
360 if (nir_op_infos
[alu
->op
].num_inputs
== 2) {
361 biv
->alu_def
= src_var
;
362 biv
->alu_op
= alu
->op
;
364 for (unsigned i
= 0; i
< 2; i
++) {
365 /* Is one of the operands const, and the other the phi */
366 if (alu
->src
[i
].src
.ssa
->parent_instr
->type
== nir_instr_type_load_const
&&
367 alu
->src
[i
].swizzle
[0] == 0 &&
368 alu
->src
[1-i
].src
.ssa
== &phi
->dest
.ssa
)
369 assert(alu
->src
[1-i
].swizzle
[0] == 0);
370 biv
->invariant
= get_loop_var(alu
->src
[i
].src
.ssa
, state
);
376 if (biv
->alu_def
&& biv
->def_outside_loop
&& biv
->invariant
&&
377 is_var_constant(biv
->def_outside_loop
)) {
378 assert(is_var_constant(biv
->invariant
));
379 biv
->alu_def
->type
= basic_induction
;
380 biv
->alu_def
->ind
= biv
;
381 var
->type
= basic_induction
;
384 found_induction_var
= true;
389 return found_induction_var
;
393 initialize_ssa_def(nir_ssa_def
*def
, void *void_state
)
395 loop_info_state
*state
= void_state
;
396 nir_loop_variable
*var
= get_loop_var(def
, state
);
398 var
->in_loop
= false;
401 if (def
->parent_instr
->type
== nir_instr_type_load_const
) {
402 var
->type
= invariant
;
404 var
->type
= undefined
;
411 find_loop_terminators(loop_info_state
*state
)
413 bool success
= false;
414 foreach_list_typed_safe(nir_cf_node
, node
, node
, &state
->loop
->body
) {
415 if (node
->type
== nir_cf_node_if
) {
416 nir_if
*nif
= nir_cf_node_as_if(node
);
418 nir_block
*break_blk
= NULL
;
419 nir_block
*continue_from_blk
= NULL
;
420 bool continue_from_then
= true;
422 nir_block
*last_then
= nir_if_last_then_block(nif
);
423 nir_block
*last_else
= nir_if_last_else_block(nif
);
424 if (nir_block_ends_in_break(last_then
)) {
425 break_blk
= last_then
;
426 continue_from_blk
= last_else
;
427 continue_from_then
= false;
428 } else if (nir_block_ends_in_break(last_else
)) {
429 break_blk
= last_else
;
430 continue_from_blk
= last_then
;
433 /* If there is a break then we should find a terminator. If we can
434 * not find a loop terminator, but there is a break-statement then
435 * we should return false so that we do not try to find trip-count
437 if (!nir_is_trivial_loop_if(nif
, break_blk
)) {
438 state
->loop
->info
->complex_loop
= true;
442 /* Continue if the if contained no jumps at all */
446 if (nif
->condition
.ssa
->parent_instr
->type
== nir_instr_type_phi
) {
447 state
->loop
->info
->complex_loop
= true;
451 nir_loop_terminator
*terminator
=
452 rzalloc(state
->loop
->info
, nir_loop_terminator
);
454 list_addtail(&terminator
->loop_terminator_link
,
455 &state
->loop
->info
->loop_terminator_list
);
457 terminator
->nif
= nif
;
458 terminator
->break_block
= break_blk
;
459 terminator
->continue_from_block
= continue_from_blk
;
460 terminator
->continue_from_then
= continue_from_then
;
461 terminator
->conditional_instr
= nif
->condition
.ssa
->parent_instr
;
470 /* This function looks for an array access within a loop that uses an
471 * induction variable for the array index. If found it returns the size of the
472 * array, otherwise 0 is returned. If we find an induction var we pass it back
473 * to the caller via array_index_out.
476 find_array_access_via_induction(loop_info_state
*state
,
477 nir_deref_instr
*deref
,
478 nir_loop_variable
**array_index_out
)
480 for (nir_deref_instr
*d
= deref
; d
; d
= nir_deref_instr_parent(d
)) {
481 if (d
->deref_type
!= nir_deref_type_array
)
484 assert(d
->arr
.index
.is_ssa
);
485 nir_loop_variable
*array_index
= get_loop_var(d
->arr
.index
.ssa
, state
);
487 if (array_index
->type
!= basic_induction
)
491 *array_index_out
= array_index
;
493 nir_deref_instr
*parent
= nir_deref_instr_parent(d
);
494 if (glsl_type_is_array_or_matrix(parent
->type
)) {
495 return glsl_get_length(parent
->type
);
497 assert(glsl_type_is_vector(parent
->type
));
498 return glsl_get_vector_elements(parent
->type
);
506 guess_loop_limit(loop_info_state
*state
, nir_const_value
*limit_val
,
507 nir_loop_variable
*basic_ind
)
509 unsigned min_array_size
= 0;
511 nir_foreach_block_in_cf_node(block
, &state
->loop
->cf_node
) {
512 nir_foreach_instr(instr
, block
) {
513 if (instr
->type
!= nir_instr_type_intrinsic
)
516 nir_intrinsic_instr
*intrin
= nir_instr_as_intrinsic(instr
);
518 /* Check for arrays variably-indexed by a loop induction variable. */
519 if (intrin
->intrinsic
== nir_intrinsic_load_deref
||
520 intrin
->intrinsic
== nir_intrinsic_store_deref
||
521 intrin
->intrinsic
== nir_intrinsic_copy_deref
) {
523 nir_loop_variable
*array_idx
= NULL
;
524 unsigned array_size
=
525 find_array_access_via_induction(state
,
526 nir_src_as_deref(intrin
->src
[0]),
528 if (basic_ind
== array_idx
&&
529 (min_array_size
== 0 || min_array_size
> array_size
)) {
530 min_array_size
= array_size
;
533 if (intrin
->intrinsic
!= nir_intrinsic_copy_deref
)
537 find_array_access_via_induction(state
,
538 nir_src_as_deref(intrin
->src
[1]),
540 if (basic_ind
== array_idx
&&
541 (min_array_size
== 0 || min_array_size
> array_size
)) {
542 min_array_size
= array_size
;
548 if (min_array_size
) {
549 *limit_val
= nir_const_value_for_uint(min_array_size
,
550 basic_ind
->def
->bit_size
);
558 try_find_limit_of_alu(nir_loop_variable
*limit
, nir_const_value
*limit_val
,
559 nir_loop_terminator
*terminator
, loop_info_state
*state
)
561 if(!is_var_alu(limit
))
564 nir_alu_instr
*limit_alu
= nir_instr_as_alu(limit
->def
->parent_instr
);
566 if (limit_alu
->op
== nir_op_imin
||
567 limit_alu
->op
== nir_op_fmin
) {
568 /* We don't handle swizzles here */
569 if (limit_alu
->src
[0].swizzle
[0] > 0 || limit_alu
->src
[1].swizzle
[0] > 0)
572 limit
= get_loop_var(limit_alu
->src
[0].src
.ssa
, state
);
574 if (!is_var_constant(limit
))
575 limit
= get_loop_var(limit_alu
->src
[1].src
.ssa
, state
);
577 if (!is_var_constant(limit
))
580 *limit_val
= nir_instr_as_load_const(limit
->def
->parent_instr
)->value
[0];
582 terminator
->exact_trip_count_unknown
= true;
590 static nir_const_value
591 eval_const_unop(nir_op op
, unsigned bit_size
, nir_const_value src0
)
593 assert(nir_op_infos
[op
].num_inputs
== 1);
594 nir_const_value dest
;
595 nir_const_value
*src
[1] = { &src0
};
596 nir_eval_const_opcode(op
, &dest
, 1, bit_size
, src
);
600 static nir_const_value
601 eval_const_binop(nir_op op
, unsigned bit_size
,
602 nir_const_value src0
, nir_const_value src1
)
604 assert(nir_op_infos
[op
].num_inputs
== 2);
605 nir_const_value dest
;
606 nir_const_value
*src
[2] = { &src0
, &src1
};
607 nir_eval_const_opcode(op
, &dest
, 1, bit_size
, src
);
612 get_iteration(nir_op cond_op
, nir_const_value initial
, nir_const_value step
,
613 nir_const_value limit
, unsigned bit_size
)
615 nir_const_value span
, iter
;
622 span
= eval_const_binop(nir_op_isub
, bit_size
, limit
, initial
);
623 iter
= eval_const_binop(nir_op_idiv
, bit_size
, span
, step
);
628 span
= eval_const_binop(nir_op_isub
, bit_size
, limit
, initial
);
629 iter
= eval_const_binop(nir_op_udiv
, bit_size
, span
, step
);
636 span
= eval_const_binop(nir_op_fsub
, bit_size
, limit
, initial
);
637 iter
= eval_const_binop(nir_op_fdiv
, bit_size
, span
, step
);
638 iter
= eval_const_unop(nir_op_f2i64
, bit_size
, iter
);
645 uint64_t iter_u64
= nir_const_value_as_uint(iter
, bit_size
);
646 return iter_u64
> INT_MAX
? -1 : (int)iter_u64
;
650 test_iterations(int32_t iter_int
, nir_const_value
*step
,
651 nir_const_value
*limit
, nir_op cond_op
, unsigned bit_size
,
652 nir_alu_type induction_base_type
,
653 nir_const_value
*initial
, bool limit_rhs
, bool invert_cond
)
655 assert(nir_op_infos
[cond_op
].num_inputs
== 2);
657 nir_const_value iter_src
;
660 switch (induction_base_type
) {
662 iter_src
= nir_const_value_for_float(iter_int
, bit_size
);
663 mul_op
= nir_op_fmul
;
664 add_op
= nir_op_fadd
;
668 iter_src
= nir_const_value_for_int(iter_int
, bit_size
);
669 mul_op
= nir_op_imul
;
670 add_op
= nir_op_iadd
;
673 unreachable("Unhandled induction variable base type!");
676 /* Multiple the iteration count we are testing by the number of times we
677 * step the induction variable each iteration.
679 nir_const_value mul_result
=
680 eval_const_binop(mul_op
, bit_size
, iter_src
, *step
);
682 /* Add the initial value to the accumulated induction variable total */
683 nir_const_value add_result
=
684 eval_const_binop(add_op
, bit_size
, mul_result
, *initial
);
686 nir_const_value
*src
[2];
687 src
[limit_rhs
? 0 : 1] = &add_result
;
688 src
[limit_rhs
? 1 : 0] = limit
;
690 /* Evaluate the loop exit condition */
691 nir_const_value result
;
692 nir_eval_const_opcode(cond_op
, &result
, 1, bit_size
, src
);
694 return invert_cond
? !result
.b
: result
.b
;
698 calculate_iterations(nir_const_value
*initial
, nir_const_value
*step
,
699 nir_const_value
*limit
, nir_loop_variable
*alu_def
,
700 nir_alu_instr
*cond_alu
, nir_op alu_op
, bool limit_rhs
,
703 assert(initial
!= NULL
&& step
!= NULL
&& limit
!= NULL
);
705 nir_alu_instr
*alu
= nir_instr_as_alu(alu_def
->def
->parent_instr
);
707 /* nir_op_isub should have been lowered away by this point */
708 assert(alu
->op
!= nir_op_isub
);
710 /* Make sure the alu type for our induction variable is compatible with the
711 * conditional alus input type. If its not something has gone really wrong.
713 nir_alu_type induction_base_type
=
714 nir_alu_type_get_base_type(nir_op_infos
[alu
->op
].output_type
);
715 if (induction_base_type
== nir_type_int
|| induction_base_type
== nir_type_uint
) {
716 assert(nir_alu_type_get_base_type(nir_op_infos
[alu_op
].input_types
[1]) == nir_type_int
||
717 nir_alu_type_get_base_type(nir_op_infos
[alu_op
].input_types
[1]) == nir_type_uint
);
719 assert(nir_alu_type_get_base_type(nir_op_infos
[alu_op
].input_types
[0]) ==
720 induction_base_type
);
723 /* Check for nsupported alu operations */
724 if (alu
->op
!= nir_op_iadd
&& alu
->op
!= nir_op_fadd
)
727 /* do-while loops can increment the starting value before the condition is
734 * Here we check if the induction variable is used directly by the loop
735 * condition and if so we assume we need to step the initial value.
737 unsigned trip_offset
= 0;
738 if (cond_alu
->src
[0].src
.ssa
== alu_def
->def
||
739 cond_alu
->src
[1].src
.ssa
== alu_def
->def
) {
743 assert(nir_src_bit_size(alu
->src
[0].src
) ==
744 nir_src_bit_size(alu
->src
[1].src
));
745 unsigned bit_size
= nir_src_bit_size(alu
->src
[0].src
);
746 int iter_int
= get_iteration(alu_op
, *initial
, *step
, *limit
, bit_size
);
748 /* If iter_int is negative the loop is ill-formed or is the conditional is
749 * unsigned with a huge iteration count so don't bother going any further.
754 /* An explanation from the GLSL unrolling pass:
756 * Make sure that the calculated number of iterations satisfies the exit
757 * condition. This is needed to catch off-by-one errors and some types of
758 * ill-formed loops. For example, we need to detect that the following
759 * loop does not have a maximum iteration count.
761 * for (float x = 0.0; x != 0.9; x += 0.2);
763 for (int bias
= -1; bias
<= 1; bias
++) {
764 const int iter_bias
= iter_int
+ bias
;
766 if (test_iterations(iter_bias
, step
, limit
, alu_op
, bit_size
,
767 induction_base_type
, initial
,
768 limit_rhs
, invert_cond
)) {
769 return iter_bias
> 0 ? iter_bias
- trip_offset
: iter_bias
;
777 inverse_comparison(nir_alu_instr
*alu
)
801 unreachable("Unsuported comparison!");
806 is_supported_terminator_condition(nir_alu_instr
*alu
)
808 return nir_alu_instr_is_comparison(alu
) &&
809 nir_op_infos
[alu
->op
].num_inputs
== 2;
813 get_induction_and_limit_vars(nir_alu_instr
*alu
, nir_loop_variable
**ind
,
814 nir_loop_variable
**limit
,
815 loop_info_state
*state
)
817 bool limit_rhs
= true;
819 /* We assume that the limit is the "right" operand */
820 *ind
= get_loop_var(alu
->src
[0].src
.ssa
, state
);
821 *limit
= get_loop_var(alu
->src
[1].src
.ssa
, state
);
823 if ((*ind
)->type
!= basic_induction
) {
824 /* We had it the wrong way, flip things around */
825 *ind
= get_loop_var(alu
->src
[1].src
.ssa
, state
);
826 *limit
= get_loop_var(alu
->src
[0].src
.ssa
, state
);
834 try_find_trip_count_vars_in_iand(nir_alu_instr
**alu
,
835 nir_loop_variable
**ind
,
836 nir_loop_variable
**limit
,
838 loop_info_state
*state
)
840 assert((*alu
)->op
== nir_op_ieq
|| (*alu
)->op
== nir_op_inot
);
842 nir_ssa_def
*iand_def
= (*alu
)->src
[0].src
.ssa
;
843 /* This is used directly in an if condition so it must be a scalar */
844 assert(iand_def
->num_components
== 1);
846 if ((*alu
)->op
== nir_op_ieq
) {
847 nir_ssa_def
*zero_def
= (*alu
)->src
[1].src
.ssa
;
849 /* We don't handle swizzles here */
850 if ((*alu
)->src
[0].swizzle
[0] > 0 || (*alu
)->src
[1].swizzle
[0] > 0)
853 if (iand_def
->parent_instr
->type
!= nir_instr_type_alu
||
854 zero_def
->parent_instr
->type
!= nir_instr_type_load_const
) {
856 /* Maybe we had it the wrong way, flip things around */
857 iand_def
= (*alu
)->src
[1].src
.ssa
;
858 zero_def
= (*alu
)->src
[0].src
.ssa
;
860 /* If we still didn't find what we need then return */
861 if (zero_def
->parent_instr
->type
!= nir_instr_type_load_const
)
865 /* If the loop is not breaking on (x && y) == 0 then return */
866 nir_const_value
*zero
=
867 nir_instr_as_load_const(zero_def
->parent_instr
)->value
;
868 if (zero
[0].i32
!= 0)
872 if (iand_def
->parent_instr
->type
!= nir_instr_type_alu
)
875 nir_alu_instr
*iand
= nir_instr_as_alu(iand_def
->parent_instr
);
876 if (iand
->op
!= nir_op_iand
)
879 /* We don't handle swizzles here */
880 if ((*alu
)->src
[0].swizzle
[0] > 0 || (*alu
)->src
[1].swizzle
[0] > 0)
883 /* Check if iand src is a terminator condition and try get induction var
884 * and trip limit var.
886 nir_ssa_def
*src
= iand
->src
[0].src
.ssa
;
887 if (src
->parent_instr
->type
== nir_instr_type_alu
) {
888 *alu
= nir_instr_as_alu(src
->parent_instr
);
889 if (is_supported_terminator_condition(*alu
))
890 *limit_rhs
= get_induction_and_limit_vars(*alu
, ind
, limit
, state
);
893 /* Try the other iand src if needed */
894 if (*ind
== NULL
|| (*ind
&& (*ind
)->type
!= basic_induction
) ||
895 !is_var_constant(*limit
)) {
896 src
= iand
->src
[1].src
.ssa
;
897 if (src
->parent_instr
->type
== nir_instr_type_alu
) {
898 nir_alu_instr
*tmp_alu
= nir_instr_as_alu(src
->parent_instr
);
899 if (is_supported_terminator_condition(tmp_alu
)) {
901 *limit_rhs
= get_induction_and_limit_vars(*alu
, ind
, limit
, state
);
907 /* Run through each of the terminators of the loop and try to infer a possible
908 * trip-count. We need to check them all, and set the lowest trip-count as the
909 * trip-count of our loop. If one of the terminators has an undecidable
910 * trip-count we can not safely assume anything about the duration of the
914 find_trip_count(loop_info_state
*state
)
916 bool trip_count_known
= true;
917 bool guessed_trip_count
= false;
918 nir_loop_terminator
*limiting_terminator
= NULL
;
919 int max_trip_count
= -1;
921 list_for_each_entry(nir_loop_terminator
, terminator
,
922 &state
->loop
->info
->loop_terminator_list
,
923 loop_terminator_link
) {
925 if (terminator
->conditional_instr
->type
!= nir_instr_type_alu
) {
926 /* If we get here the loop is dead and will get cleaned up by the
927 * nir_opt_dead_cf pass.
929 trip_count_known
= false;
933 nir_alu_instr
*alu
= nir_instr_as_alu(terminator
->conditional_instr
);
934 nir_op alu_op
= alu
->op
;
937 nir_loop_variable
*basic_ind
= NULL
;
938 nir_loop_variable
*limit
;
939 if (alu
->op
== nir_op_inot
|| alu
->op
== nir_op_ieq
) {
940 nir_alu_instr
*new_alu
= alu
;
941 try_find_trip_count_vars_in_iand(&new_alu
, &basic_ind
, &limit
,
944 /* The loop is exiting on (x && y) == 0 so we need to get the
945 * inverse of x or y (i.e. which ever contained the induction var) in
946 * order to compute the trip count.
948 if (basic_ind
&& basic_ind
->type
== basic_induction
) {
950 alu_op
= inverse_comparison(alu
);
951 trip_count_known
= false;
952 terminator
->exact_trip_count_unknown
= true;
957 if (!is_supported_terminator_condition(alu
)) {
958 trip_count_known
= false;
962 limit_rhs
= get_induction_and_limit_vars(alu
, &basic_ind
, &limit
,
966 /* The comparison has to have a basic induction variable for us to be
967 * able to find trip counts.
969 if (basic_ind
->type
!= basic_induction
) {
970 trip_count_known
= false;
974 terminator
->induction_rhs
= !limit_rhs
;
976 /* Attempt to find a constant limit for the loop */
977 nir_const_value limit_val
;
978 if (is_var_constant(limit
)) {
980 nir_instr_as_load_const(limit
->def
->parent_instr
)->value
[0];
982 trip_count_known
= false;
984 if (!try_find_limit_of_alu(limit
, &limit_val
, terminator
, state
)) {
985 /* Guess loop limit based on array access */
986 if (!guess_loop_limit(state
, &limit_val
, basic_ind
)) {
990 guessed_trip_count
= true;
994 /* We have determined that we have the following constants:
995 * (With the typical int i = 0; i < x; i++; as an example)
998 * - Step / iteration size
999 * Thats all thats needed to calculate the trip-count
1002 nir_const_value
*initial_val
=
1003 nir_instr_as_load_const(basic_ind
->ind
->def_outside_loop
->
1004 def
->parent_instr
)->value
;
1006 nir_const_value
*step_val
=
1007 nir_instr_as_load_const(basic_ind
->ind
->invariant
->def
->
1008 parent_instr
)->value
;
1010 int iterations
= calculate_iterations(initial_val
, step_val
,
1012 basic_ind
->ind
->alu_def
, alu
,
1014 terminator
->continue_from_then
);
1016 /* Where we not able to calculate the iteration count */
1017 if (iterations
== -1) {
1018 trip_count_known
= false;
1019 guessed_trip_count
= false;
1023 if (guessed_trip_count
) {
1024 guessed_trip_count
= false;
1025 if (state
->loop
->info
->guessed_trip_count
== 0 ||
1026 state
->loop
->info
->guessed_trip_count
> iterations
)
1027 state
->loop
->info
->guessed_trip_count
= iterations
;
1032 /* If this is the first run or we have found a smaller amount of
1033 * iterations than previously (we have identified a more limiting
1034 * terminator) set the trip count and limiting terminator.
1036 if (max_trip_count
== -1 || iterations
< max_trip_count
) {
1037 max_trip_count
= iterations
;
1038 limiting_terminator
= terminator
;
1042 state
->loop
->info
->exact_trip_count_known
= trip_count_known
;
1043 if (max_trip_count
> -1)
1044 state
->loop
->info
->max_trip_count
= max_trip_count
;
1045 state
->loop
->info
->limiting_terminator
= limiting_terminator
;
1049 force_unroll_array_access(loop_info_state
*state
, nir_deref_instr
*deref
)
1051 unsigned array_size
= find_array_access_via_induction(state
, deref
, NULL
);
1053 if (array_size
== state
->loop
->info
->max_trip_count
)
1056 if (deref
->mode
& state
->indirect_mask
)
1064 force_unroll_heuristics(loop_info_state
*state
, nir_block
*block
)
1066 nir_foreach_instr(instr
, block
) {
1067 if (instr
->type
!= nir_instr_type_intrinsic
)
1070 nir_intrinsic_instr
*intrin
= nir_instr_as_intrinsic(instr
);
1072 /* Check for arrays variably-indexed by a loop induction variable.
1073 * Unrolling the loop may convert that access into constant-indexing.
1075 if (intrin
->intrinsic
== nir_intrinsic_load_deref
||
1076 intrin
->intrinsic
== nir_intrinsic_store_deref
||
1077 intrin
->intrinsic
== nir_intrinsic_copy_deref
) {
1078 if (force_unroll_array_access(state
,
1079 nir_src_as_deref(intrin
->src
[0])))
1082 if (intrin
->intrinsic
== nir_intrinsic_copy_deref
&&
1083 force_unroll_array_access(state
,
1084 nir_src_as_deref(intrin
->src
[1])))
1093 get_loop_info(loop_info_state
*state
, nir_function_impl
*impl
)
1095 nir_shader
*shader
= impl
->function
->shader
;
1096 const nir_shader_compiler_options
*options
= shader
->options
;
1098 /* Initialize all variables to "outside_loop". This also marks defs
1099 * invariant and constant if they are nir_instr_type_load_consts
1101 nir_foreach_block(block
, impl
) {
1102 nir_foreach_instr(instr
, block
)
1103 nir_foreach_ssa_def(instr
, initialize_ssa_def
, state
);
1106 /* Add all entries in the outermost part of the loop to the processing list
1107 * Mark the entries in conditionals or in nested loops accordingly
1109 foreach_list_typed_safe(nir_cf_node
, node
, node
, &state
->loop
->body
) {
1110 switch (node
->type
) {
1112 case nir_cf_node_block
:
1113 init_loop_block(nir_cf_node_as_block(node
), state
,
1114 false, false, options
);
1117 case nir_cf_node_if
:
1118 nir_foreach_block_in_cf_node(block
, node
)
1119 init_loop_block(block
, state
, true, false, options
);
1122 case nir_cf_node_loop
:
1123 nir_foreach_block_in_cf_node(block
, node
) {
1124 init_loop_block(block
, state
, false, true, options
);
1128 case nir_cf_node_function
:
1133 /* Try to find all simple terminators of the loop. If we can't find any,
1134 * or we find possible terminators that have side effects then bail.
1136 if (!find_loop_terminators(state
)) {
1137 list_for_each_entry_safe(nir_loop_terminator
, terminator
,
1138 &state
->loop
->info
->loop_terminator_list
,
1139 loop_terminator_link
) {
1140 list_del(&terminator
->loop_terminator_link
);
1141 ralloc_free(terminator
);
1146 /* Induction analysis needs invariance information so get that first */
1147 compute_invariance_information(state
);
1149 /* We have invariance information so try to find induction variables */
1150 if (!compute_induction_information(state
))
1153 /* Run through each of the terminators and try to compute a trip-count */
1154 find_trip_count(state
);
1156 nir_foreach_block_in_cf_node(block
, &state
->loop
->cf_node
) {
1157 if (force_unroll_heuristics(state
, block
)) {
1158 state
->loop
->info
->force_unroll
= true;
1164 static loop_info_state
*
1165 initialize_loop_info_state(nir_loop
*loop
, void *mem_ctx
,
1166 nir_function_impl
*impl
)
1168 loop_info_state
*state
= rzalloc(mem_ctx
, loop_info_state
);
1169 state
->loop_vars
= rzalloc_array(mem_ctx
, nir_loop_variable
,
1173 list_inithead(&state
->process_list
);
1176 ralloc_free(loop
->info
);
1178 loop
->info
= rzalloc(loop
, nir_loop_info
);
1180 list_inithead(&loop
->info
->loop_terminator_list
);
1186 process_loops(nir_cf_node
*cf_node
, nir_variable_mode indirect_mask
)
1188 switch (cf_node
->type
) {
1189 case nir_cf_node_block
:
1191 case nir_cf_node_if
: {
1192 nir_if
*if_stmt
= nir_cf_node_as_if(cf_node
);
1193 foreach_list_typed(nir_cf_node
, nested_node
, node
, &if_stmt
->then_list
)
1194 process_loops(nested_node
, indirect_mask
);
1195 foreach_list_typed(nir_cf_node
, nested_node
, node
, &if_stmt
->else_list
)
1196 process_loops(nested_node
, indirect_mask
);
1199 case nir_cf_node_loop
: {
1200 nir_loop
*loop
= nir_cf_node_as_loop(cf_node
);
1201 foreach_list_typed(nir_cf_node
, nested_node
, node
, &loop
->body
)
1202 process_loops(nested_node
, indirect_mask
);
1206 unreachable("unknown cf node type");
1209 nir_loop
*loop
= nir_cf_node_as_loop(cf_node
);
1210 nir_function_impl
*impl
= nir_cf_node_get_function(cf_node
);
1211 void *mem_ctx
= ralloc_context(NULL
);
1213 loop_info_state
*state
= initialize_loop_info_state(loop
, mem_ctx
, impl
);
1214 state
->indirect_mask
= indirect_mask
;
1216 get_loop_info(state
, impl
);
1218 ralloc_free(mem_ctx
);
1222 nir_loop_analyze_impl(nir_function_impl
*impl
,
1223 nir_variable_mode indirect_mask
)
1225 nir_index_ssa_defs(impl
);
1226 foreach_list_typed(nir_cf_node
, node
, node
, &impl
->body
)
1227 process_loops(node
, indirect_mask
);