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24 #include "glsl_types.h"
25 #include "loop_analysis.h"
26 #include "ir_hierarchical_visitor.h"
28 class loop_unroll_visitor
: public ir_hierarchical_visitor
{
30 loop_unroll_visitor(loop_state
*state
, unsigned max_iterations
)
33 this->progress
= false;
34 this->max_iterations
= max_iterations
;
37 virtual ir_visitor_status
visit_leave(ir_loop
*ir
);
42 unsigned max_iterations
;
47 is_break(ir_instruction
*ir
)
49 return ir
!= NULL
&& ir
->ir_type
== ir_type_loop_jump
50 && ((ir_loop_jump
*) ir
)->is_break();
55 loop_unroll_visitor::visit_leave(ir_loop
*ir
)
57 loop_variable_state
*const ls
= this->state
->get(ir
);
61 /* If we've entered a loop that hasn't been analyzed, something really,
62 * really bad has happened.
66 return visit_continue
;
69 iterations
= ls
->max_iterations
;
71 /* Don't try to unroll loops where the number of iterations is not known
75 return visit_continue
;
77 /* Don't try to unroll loops that have zillions of iterations either.
79 if (iterations
> (int) max_iterations
)
80 return visit_continue
;
82 /* Don't try to unroll nested loops and loops with a huge body.
85 foreach_list(node
, &ir
->body_instructions
) {
88 /* If the loop body gets to huge, do not unroll. */
89 if (5*max_iterations
< ir_count
*iterations
)
90 return visit_continue
;
91 /* Do not unroll loops with child loop nodes. */
92 if (((ir_instruction
*) node
)->as_loop())
93 return visit_continue
;
96 if (ls
->num_loop_jumps
> 1)
97 return visit_continue
;
98 else if (ls
->num_loop_jumps
) {
99 ir_instruction
*last_ir
= (ir_instruction
*) ir
->body_instructions
.get_tail();
100 assert(last_ir
!= NULL
);
102 if (is_break(last_ir
)) {
103 /* If the only loop-jump is a break at the end of the loop, the loop
104 * will execute exactly once. Remove the break, set the iteration
105 * count, and fall through to the normal unroller.
110 this->progress
= true;
113 ir_instruction
*break_ir
= NULL
;
114 bool continue_from_then_branch
= false;
116 foreach_list(node
, &ir
->body_instructions
) {
117 /* recognize loops in the form produced by ir_lower_jumps */
118 ir_instruction
*cur_ir
= (ir_instruction
*) node
;
120 ir_if
= cur_ir
->as_if();
122 /* Determine which if-statement branch, if any, ends with a
123 * break. The branch that did *not* have the break will get a
124 * temporary continue inserted in each iteration of the loop
127 * Note that since ls->num_loop_jumps is <= 1, it is impossible
128 * for both branches to end with a break.
130 ir_instruction
*ir_if_last
=
131 (ir_instruction
*) ir_if
->then_instructions
.get_tail();
133 if (is_break(ir_if_last
)) {
134 continue_from_then_branch
= false;
135 break_ir
= ir_if_last
;
139 (ir_instruction
*) ir_if
->else_instructions
.get_tail();
141 if (is_break(ir_if_last
)) {
142 break_ir
= ir_if_last
;
143 continue_from_then_branch
= true;
150 if (break_ir
== NULL
)
151 return visit_continue
;
153 /* move instructions after then if in the continue branch */
154 while (!ir_if
->get_next()->is_tail_sentinel()) {
155 ir_instruction
*move_ir
= (ir_instruction
*) ir_if
->get_next();
158 if (continue_from_then_branch
)
159 ir_if
->then_instructions
.push_tail(move_ir
);
161 ir_if
->else_instructions
.push_tail(move_ir
);
164 /* Remove the break from the if-statement.
168 void *const mem_ctx
= ralloc_parent(ir
);
169 ir_instruction
*ir_to_replace
= ir
;
171 for (int i
= 0; i
< iterations
; i
++) {
174 copy_list
.make_empty();
175 clone_ir_list(mem_ctx
, ©_list
, &ir
->body_instructions
);
177 ir_if
= ((ir_instruction
*) copy_list
.get_tail())->as_if();
178 assert(ir_if
!= NULL
);
180 ir_to_replace
->insert_before(©_list
);
181 ir_to_replace
->remove();
183 /* placeholder that will be removed in the next iteration */
185 new(mem_ctx
) ir_loop_jump(ir_loop_jump::jump_continue
);
187 exec_list
*const list
= (continue_from_then_branch
)
188 ? &ir_if
->then_instructions
: &ir_if
->else_instructions
;
190 list
->push_tail(ir_to_replace
);
193 ir_to_replace
->remove();
195 this->progress
= true;
196 return visit_continue
;
200 void *const mem_ctx
= ralloc_parent(ir
);
202 for (int i
= 0; i
< iterations
; i
++) {
205 copy_list
.make_empty();
206 clone_ir_list(mem_ctx
, ©_list
, &ir
->body_instructions
);
208 ir
->insert_before(©_list
);
211 /* The loop has been replaced by the unrolled copies. Remove the original
212 * loop from the IR sequence.
216 this->progress
= true;
217 return visit_continue
;
222 unroll_loops(exec_list
*instructions
, loop_state
*ls
, unsigned max_iterations
)
224 loop_unroll_visitor
v(ls
, max_iterations
);