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24 #include "glsl_types.h"
25 #include "loop_analysis.h"
26 #include "ir_hierarchical_visitor.h"
28 #include "main/mtypes.h"
32 class loop_unroll_visitor
: public ir_hierarchical_visitor
{
34 loop_unroll_visitor(loop_state
*state
,
35 const struct gl_shader_compiler_options
*options
)
38 this->progress
= false;
39 this->options
= options
;
42 virtual ir_visitor_status
visit_leave(ir_loop
*ir
);
43 void simple_unroll(ir_loop
*ir
, int iterations
);
44 void complex_unroll(ir_loop
*ir
, int iterations
,
45 bool continue_from_then_branch
);
46 void splice_post_if_instructions(ir_if
*ir_if
, exec_list
*splice_dest
);
51 const struct gl_shader_compiler_options
*options
;
54 } /* anonymous namespace */
57 is_break(ir_instruction
*ir
)
59 return ir
!= NULL
&& ir
->ir_type
== ir_type_loop_jump
60 && ((ir_loop_jump
*) ir
)->is_break();
63 class loop_unroll_count
: public ir_hierarchical_visitor
{
66 bool unsupported_variable_indexing
;
67 bool array_indexed_by_induction_var_with_exact_iterations
;
68 /* If there are nested loops, the node count will be inaccurate. */
71 loop_unroll_count(exec_list
*list
, loop_variable_state
*ls
,
72 const struct gl_shader_compiler_options
*options
)
73 : ls(ls
), options(options
)
77 unsupported_variable_indexing
= false;
78 array_indexed_by_induction_var_with_exact_iterations
= false;
83 virtual ir_visitor_status
visit_enter(ir_assignment
*)
86 return visit_continue
;
89 virtual ir_visitor_status
visit_enter(ir_expression
*)
92 return visit_continue
;
95 virtual ir_visitor_status
visit_enter(ir_loop
*)
98 return visit_continue
;
101 virtual ir_visitor_status
visit_enter(ir_dereference_array
*ir
)
103 /* Check for arrays variably-indexed by a loop induction variable.
104 * Unrolling the loop may convert that access into constant-indexing.
106 * Many drivers don't support particular kinds of variable indexing,
107 * and have to resort to using lower_variable_index_to_cond_assign to
108 * handle it. This results in huge amounts of horrible code, so we'd
109 * like to avoid that if possible. Here, we just note that it will
112 if ((ir
->array
->type
->is_array() || ir
->array
->type
->is_matrix()) &&
113 !ir
->array_index
->as_constant()) {
114 ir_variable
*array
= ir
->array
->variable_referenced();
115 loop_variable
*lv
= ls
->get(ir
->array_index
->variable_referenced());
116 if (array
&& lv
&& lv
->is_induction_var()) {
117 /* If an array is indexed by a loop induction variable, and the
118 * array size is exactly the number of loop iterations, this is
119 * probably a simple for-loop trying to access each element in
120 * turn; the application may expect it to be unrolled.
122 if (int(array
->type
->length
) == ls
->limiting_terminator
->iterations
)
123 array_indexed_by_induction_var_with_exact_iterations
= true;
125 switch (array
->data
.mode
) {
127 case ir_var_temporary
:
128 case ir_var_const_in
:
129 case ir_var_function_in
:
130 case ir_var_function_out
:
131 case ir_var_function_inout
:
132 if (options
->EmitNoIndirectTemp
)
133 unsupported_variable_indexing
= true;
136 if (options
->EmitNoIndirectUniform
)
137 unsupported_variable_indexing
= true;
139 case ir_var_shader_in
:
140 if (options
->EmitNoIndirectInput
)
141 unsupported_variable_indexing
= true;
143 case ir_var_shader_out
:
144 if (options
->EmitNoIndirectOutput
)
145 unsupported_variable_indexing
= true;
150 return visit_continue
;
154 loop_variable_state
*ls
;
155 const struct gl_shader_compiler_options
*options
;
160 * Unroll a loop which does not contain any jumps. For example, if the input
163 * (loop (...) ...instrs...)
165 * And the iteration count is 3, the output will be:
167 * ...instrs... ...instrs... ...instrs...
170 loop_unroll_visitor::simple_unroll(ir_loop
*ir
, int iterations
)
172 void *const mem_ctx
= ralloc_parent(ir
);
174 for (int i
= 0; i
< iterations
; i
++) {
177 copy_list
.make_empty();
178 clone_ir_list(mem_ctx
, ©_list
, &ir
->body_instructions
);
180 ir
->insert_before(©_list
);
183 /* The loop has been replaced by the unrolled copies. Remove the original
184 * loop from the IR sequence.
188 this->progress
= true;
193 * Unroll a loop whose last statement is an ir_if. If \c
194 * continue_from_then_branch is true, the loop is repeated only when the
195 * "then" branch of the if is taken; otherwise it is repeated only when the
196 * "else" branch of the if is taken.
198 * For example, if the input is:
203 * (...then_instrs...)
204 * (...else_instrs...)))
206 * And the iteration count is 3, and \c continue_from_then_branch is true,
207 * then the output will be:
217 * (...then_instrs...)
218 * (...else_instrs...)))
219 * (...else_instrs...)))
223 loop_unroll_visitor::complex_unroll(ir_loop
*ir
, int iterations
,
224 bool continue_from_then_branch
)
226 void *const mem_ctx
= ralloc_parent(ir
);
227 ir_instruction
*ir_to_replace
= ir
;
229 for (int i
= 0; i
< iterations
; i
++) {
232 copy_list
.make_empty();
233 clone_ir_list(mem_ctx
, ©_list
, &ir
->body_instructions
);
235 ir_if
*ir_if
= ((ir_instruction
*) copy_list
.get_tail())->as_if();
236 assert(ir_if
!= NULL
);
238 ir_to_replace
->insert_before(©_list
);
239 ir_to_replace
->remove();
241 /* placeholder that will be removed in the next iteration */
243 new(mem_ctx
) ir_loop_jump(ir_loop_jump::jump_continue
);
245 exec_list
*const list
= (continue_from_then_branch
)
246 ? &ir_if
->then_instructions
: &ir_if
->else_instructions
;
248 list
->push_tail(ir_to_replace
);
251 ir_to_replace
->remove();
253 this->progress
= true;
258 * Move all of the instructions which follow \c ir_if to the end of
261 * For example, in the code snippet:
264 * (...then_instructions...
266 * (...else_instructions...))
267 * ...post_if_instructions...
269 * If \c ir_if points to the "if" instruction, and \c splice_dest points to
270 * (...else_instructions...), the code snippet is transformed into:
273 * (...then_instructions...
275 * (...else_instructions...
276 * ...post_if_instructions...))
279 loop_unroll_visitor::splice_post_if_instructions(ir_if
*ir_if
,
280 exec_list
*splice_dest
)
282 while (!ir_if
->get_next()->is_tail_sentinel()) {
283 ir_instruction
*move_ir
= (ir_instruction
*) ir_if
->get_next();
286 splice_dest
->push_tail(move_ir
);
292 loop_unroll_visitor::visit_leave(ir_loop
*ir
)
294 loop_variable_state
*const ls
= this->state
->get(ir
);
297 /* If we've entered a loop that hasn't been analyzed, something really,
298 * really bad has happened.
302 return visit_continue
;
305 /* Don't try to unroll loops where the number of iterations is not known
308 if (ls
->limiting_terminator
== NULL
)
309 return visit_continue
;
311 iterations
= ls
->limiting_terminator
->iterations
;
313 const int max_iterations
= options
->MaxUnrollIterations
;
315 /* Don't try to unroll loops that have zillions of iterations either.
317 if (iterations
> max_iterations
)
318 return visit_continue
;
320 /* Don't try to unroll nested loops and loops with a huge body.
322 loop_unroll_count
count(&ir
->body_instructions
, ls
, options
);
324 bool loop_too_large
=
325 count
.nested_loop
|| count
.nodes
* iterations
> max_iterations
* 5;
327 if (loop_too_large
&& !count
.unsupported_variable_indexing
&&
328 !count
.array_indexed_by_induction_var_with_exact_iterations
)
329 return visit_continue
;
331 /* Note: the limiting terminator contributes 1 to ls->num_loop_jumps.
332 * We'll be removing the limiting terminator before we unroll.
334 assert(ls
->num_loop_jumps
> 0);
335 unsigned predicted_num_loop_jumps
= ls
->num_loop_jumps
- 1;
337 if (predicted_num_loop_jumps
> 1)
338 return visit_continue
;
340 if (predicted_num_loop_jumps
== 0) {
341 ls
->limiting_terminator
->ir
->remove();
342 simple_unroll(ir
, iterations
);
343 return visit_continue
;
346 ir_instruction
*last_ir
= (ir_instruction
*) ir
->body_instructions
.get_tail();
347 assert(last_ir
!= NULL
);
349 if (is_break(last_ir
)) {
350 /* If the only loop-jump is a break at the end of the loop, the loop
351 * will execute exactly once. Remove the break and use the simple
352 * unroller with an iteration count of 1.
356 ls
->limiting_terminator
->ir
->remove();
357 simple_unroll(ir
, 1);
358 return visit_continue
;
361 /* recognize loops in the form produced by ir_lower_jumps */
362 foreach_in_list(ir_instruction
, cur_ir
, &ir
->body_instructions
) {
363 /* Skip the limiting terminator, since it will go away when we
366 if (cur_ir
== ls
->limiting_terminator
->ir
)
369 ir_if
*ir_if
= cur_ir
->as_if();
371 /* Determine which if-statement branch, if any, ends with a
372 * break. The branch that did *not* have the break will get a
373 * temporary continue inserted in each iteration of the loop
376 * Note that since ls->num_loop_jumps is <= 1, it is impossible
377 * for both branches to end with a break.
379 ir_instruction
*ir_if_last
=
380 (ir_instruction
*) ir_if
->then_instructions
.get_tail();
382 if (is_break(ir_if_last
)) {
383 ls
->limiting_terminator
->ir
->remove();
384 splice_post_if_instructions(ir_if
, &ir_if
->else_instructions
);
385 ir_if_last
->remove();
386 complex_unroll(ir
, iterations
, false);
387 return visit_continue
;
390 (ir_instruction
*) ir_if
->else_instructions
.get_tail();
392 if (is_break(ir_if_last
)) {
393 ls
->limiting_terminator
->ir
->remove();
394 splice_post_if_instructions(ir_if
, &ir_if
->then_instructions
);
395 ir_if_last
->remove();
396 complex_unroll(ir
, iterations
, true);
397 return visit_continue
;
403 /* Did not find the break statement. It must be in a complex if-nesting,
404 * so don't try to unroll.
406 return visit_continue
;
411 unroll_loops(exec_list
*instructions
, loop_state
*ls
,
412 const struct gl_shader_compiler_options
*options
)
414 loop_unroll_visitor
v(ls
, options
);