2 * Copyright © 2010 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
21 * DEALINGS IN THE SOFTWARE.
24 #include "glsl_types.h"
25 #include "loop_analysis.h"
26 #include "ir_hierarchical_visitor.h"
28 static bool is_loop_terminator(ir_if
*ir
);
30 static bool all_expression_operands_are_loop_constant(ir_rvalue
*,
33 static ir_rvalue
*get_basic_induction_increment(ir_assignment
*, hash_table
*);
36 loop_state::loop_state()
38 this->ht
= hash_table_ctor(0, hash_table_pointer_hash
,
39 hash_table_pointer_compare
);
40 this->mem_ctx
= talloc_init("loop state");
44 loop_state::~loop_state()
46 hash_table_dtor(this->ht
);
47 talloc_free(this->mem_ctx
);
52 loop_state::insert(ir_loop
*ir
)
54 loop_variable_state
*ls
= new(this->mem_ctx
) loop_variable_state
;
55 hash_table_insert(this->ht
, ls
, ir
);
62 loop_state::get(const ir_loop
*ir
)
64 return (loop_variable_state
*) hash_table_find(this->ht
, ir
);
69 loop_variable_state::get(const ir_variable
*ir
)
71 return (loop_variable
*) hash_table_find(this->var_hash
, ir
);
76 loop_variable_state::insert(ir_variable
*var
)
78 void *mem_ctx
= talloc_parent(this);
79 loop_variable
*lv
= talloc_zero(mem_ctx
, loop_variable
);
83 hash_table_insert(this->var_hash
, lv
, lv
->var
);
84 this->variables
.push_tail(lv
);
91 loop_variable_state::insert(ir_if
*if_stmt
)
93 void *mem_ctx
= talloc_parent(this);
94 loop_terminator
*t
= talloc_zero(mem_ctx
, loop_terminator
);
97 this->terminators
.push_tail(t
);
103 class loop_analysis
: public ir_hierarchical_visitor
{
107 virtual ir_visitor_status
visit(ir_loop_jump
*);
108 virtual ir_visitor_status
visit(ir_dereference_variable
*);
110 virtual ir_visitor_status
visit_enter(ir_loop
*);
111 virtual ir_visitor_status
visit_leave(ir_loop
*);
112 virtual ir_visitor_status
visit_enter(ir_assignment
*);
113 virtual ir_visitor_status
visit_leave(ir_assignment
*);
114 virtual ir_visitor_status
visit_enter(ir_if
*);
115 virtual ir_visitor_status
visit_leave(ir_if
*);
119 int if_statement_depth
;
121 ir_assignment
*current_assignment
;
127 loop_analysis::loop_analysis()
129 this->loops
= new loop_state
;
131 this->if_statement_depth
= 0;
132 this->current_assignment
= NULL
;
137 loop_analysis::visit(ir_loop_jump
*ir
)
141 assert(!this->state
.is_empty());
143 loop_variable_state
*const ls
=
144 (loop_variable_state
*) this->state
.get_head();
146 ls
->num_loop_jumps
++;
148 return visit_continue
;
153 loop_analysis::visit(ir_dereference_variable
*ir
)
155 /* If we're not somewhere inside a loop, there's nothing to do.
157 if (this->state
.is_empty())
158 return visit_continue
;
160 loop_variable_state
*const ls
=
161 (loop_variable_state
*) this->state
.get_head();
163 ir_variable
*var
= ir
->variable_referenced();
164 loop_variable
*lv
= ls
->get(var
);
167 lv
= ls
->insert(var
);
168 lv
->read_before_write
= !this->in_assignee
;
171 if (this->in_assignee
) {
172 assert(this->current_assignment
!= NULL
);
174 lv
->conditional_assignment
= (this->if_statement_depth
> 0)
175 || (this->current_assignment
->condition
!= NULL
);
177 if (lv
->first_assignment
== NULL
) {
178 assert(lv
->num_assignments
== 0);
180 lv
->first_assignment
= this->current_assignment
;
183 lv
->num_assignments
++;
184 } else if (lv
->first_assignment
== this->current_assignment
) {
185 /* This catches the case where the variable is used in the RHS of an
186 * assignment where it is also in the LHS.
188 lv
->read_before_write
= true;
191 return visit_continue
;
195 loop_analysis::visit_enter(ir_loop
*ir
)
197 loop_variable_state
*ls
= this->loops
->insert(ir
);
198 this->state
.push_head(ls
);
200 return visit_continue
;
204 loop_analysis::visit_leave(ir_loop
*ir
)
206 loop_variable_state
*const ls
=
207 (loop_variable_state
*) this->state
.pop_head();
210 foreach_list(node
, &ir
->body_instructions
) {
211 /* Skip over declarations at the start of a loop.
213 if (((ir_instruction
*) node
)->as_variable())
216 ir_if
*if_stmt
= ((ir_instruction
*) node
)->as_if();
218 if ((if_stmt
!= NULL
) && is_loop_terminator(if_stmt
))
225 foreach_list_safe(node
, &ls
->variables
) {
226 loop_variable
*lv
= (loop_variable
*) node
;
228 /* Move variables that are already marked as being loop constant to
229 * a separate list. These trivially don't need to be tested.
231 if (lv
->is_loop_constant()) {
233 ls
->constants
.push_tail(lv
);
237 /* Each variable assigned in the loop that isn't already marked as being loop
238 * constant might still be loop constant. The requirements at this point
241 * - Variable is written before it is read.
243 * - Only one assignment to the variable.
245 * - All operands on the RHS of the assignment are also loop constants.
247 * The last requirement is the reason for the progress loop. A variable
248 * marked as a loop constant on one pass may allow other variables to be
249 * marked as loop constant on following passes.
255 foreach_list_safe(node
, &ls
->variables
) {
256 loop_variable
*lv
= (loop_variable
*) node
;
258 if (lv
->conditional_assignment
|| (lv
->num_assignments
> 1))
261 /* Process the RHS of the assignment. If all of the variables
262 * accessed there are loop constants, then add this
264 ir_rvalue
*const rhs
= lv
->first_assignment
->rhs
;
265 if (all_expression_operands_are_loop_constant(rhs
, ls
->var_hash
)) {
266 lv
->rhs_clean
= true;
268 if (lv
->is_loop_constant()) {
272 ls
->constants
.push_tail(lv
);
278 /* The remaining variables that are not loop invariant might be loop
279 * induction variables.
281 foreach_list_safe(node
, &ls
->variables
) {
282 loop_variable
*lv
= (loop_variable
*) node
;
284 /* If there is more than one assignment to a variable, it cannot be a
285 * loop induction variable. This isn't strictly true, but this is a
286 * very simple induction variable detector, and it can't handle more
289 if (lv
->num_assignments
> 1)
292 /* All of the variables with zero assignments in the loop are loop
293 * invariant, and they should have already been filtered out.
295 assert(lv
->num_assignments
== 1);
296 assert(lv
->first_assignment
!= NULL
);
298 /* The assignmnet to the variable in the loop must be unconditional.
300 if (lv
->conditional_assignment
)
303 /* Basic loop induction variables have a single assignment in the loop
304 * that has the form 'VAR = VAR + i' or 'VAR = VAR - i' where i is a
307 ir_rvalue
*const inc
=
308 get_basic_induction_increment(lv
->first_assignment
, ls
->var_hash
);
315 ls
->induction_variables
.push_tail(lv
);
319 return visit_continue
;
323 loop_analysis::visit_enter(ir_if
*ir
)
327 if (!this->state
.is_empty())
328 this->if_statement_depth
++;
330 return visit_continue
;
334 loop_analysis::visit_leave(ir_if
*ir
)
338 if (!this->state
.is_empty())
339 this->if_statement_depth
--;
341 return visit_continue
;
345 loop_analysis::visit_enter(ir_assignment
*ir
)
347 /* If we're not somewhere inside a loop, there's nothing to do.
349 if (this->state
.is_empty())
350 return visit_continue_with_parent
;
352 this->current_assignment
= ir
;
354 return visit_continue
;
358 loop_analysis::visit_leave(ir_assignment
*ir
)
360 /* Since the visit_enter exits with visit_continue_with_parent for this
361 * case, the loop state stack should never be empty here.
363 assert(!this->state
.is_empty());
365 assert(this->current_assignment
== ir
);
366 this->current_assignment
= NULL
;
368 return visit_continue
;
372 class examine_rhs
: public ir_hierarchical_visitor
{
374 examine_rhs(hash_table
*loop_variables
)
376 this->only_uses_loop_constants
= true;
377 this->loop_variables
= loop_variables
;
380 virtual ir_visitor_status
visit(ir_dereference_variable
*ir
)
383 (loop_variable
*) hash_table_find(this->loop_variables
, ir
->var
);
387 if (lv
->is_loop_constant()) {
388 return visit_continue
;
390 this->only_uses_loop_constants
= false;
395 hash_table
*loop_variables
;
396 bool only_uses_loop_constants
;
401 all_expression_operands_are_loop_constant(ir_rvalue
*ir
, hash_table
*variables
)
403 examine_rhs
v(variables
);
407 return v
.only_uses_loop_constants
;
412 get_basic_induction_increment(ir_assignment
*ir
, hash_table
*var_hash
)
414 /* The RHS must be a binary expression.
416 ir_expression
*const rhs
= ir
->rhs
->as_expression();
418 || ((rhs
->operation
!= ir_binop_add
)
419 && (rhs
->operation
!= ir_binop_sub
)))
422 /* One of the of operands of the expression must be the variable assigned.
423 * If the operation is subtraction, the variable in question must be the
426 ir_variable
*const var
= ir
->lhs
->variable_referenced();
428 ir_variable
*const op0
= rhs
->operands
[0]->variable_referenced();
429 ir_variable
*const op1
= rhs
->operands
[1]->variable_referenced();
431 if (((op0
!= var
) && (op1
!= var
))
432 || ((op1
== var
) && (rhs
->operation
== ir_binop_sub
)))
435 ir_rvalue
*inc
= (op0
== var
) ? rhs
->operands
[1] : rhs
->operands
[0];
437 if (inc
->as_constant() == NULL
) {
438 ir_variable
*const inc_var
= inc
->variable_referenced();
439 if (inc_var
!= NULL
) {
441 (loop_variable
*) hash_table_find(var_hash
, inc_var
);
443 if (!lv
->is_loop_constant())
449 if ((inc
!= NULL
) && (rhs
->operation
== ir_binop_sub
)) {
450 void *mem_ctx
= talloc_parent(ir
);
452 inc
= new(mem_ctx
) ir_expression(ir_unop_neg
,
454 inc
->clone(mem_ctx
, NULL
),
463 * Detect whether an if-statement is a loop terminating condition
465 * Detects if-statements of the form
467 * (if (expression bool ...) (break))
470 is_loop_terminator(ir_if
*ir
)
472 if (!ir
->else_instructions
.is_empty())
475 ir_instruction
*const inst
=
476 (ir_instruction
*) ir
->then_instructions
.get_head();
477 assert(inst
!= NULL
);
479 if (inst
->ir_type
!= ir_type_loop_jump
)
482 ir_loop_jump
*const jump
= (ir_loop_jump
*) inst
;
483 if (jump
->mode
!= ir_loop_jump::jump_break
)
491 analyze_loop_variables(exec_list
*instructions
)