diff options
Diffstat (limited to 'mesalib/src/glsl/loop_unroll.cpp')
| -rw-r--r-- | mesalib/src/glsl/loop_unroll.cpp | 318 |
1 files changed, 205 insertions, 113 deletions
diff --git a/mesalib/src/glsl/loop_unroll.cpp b/mesalib/src/glsl/loop_unroll.cpp index ff97766f1..6eced1736 100644 --- a/mesalib/src/glsl/loop_unroll.cpp +++ b/mesalib/src/glsl/loop_unroll.cpp @@ -37,6 +37,10 @@ public: } virtual ir_visitor_status visit_leave(ir_loop *ir); + void simple_unroll(ir_loop *ir, int iterations); + void complex_unroll(ir_loop *ir, int iterations, + bool continue_from_then_branch); + void splice_post_if_instructions(ir_if *ir_if, exec_list *splice_dest); loop_state *state; @@ -86,6 +90,138 @@ public: }; +/** + * Unroll a loop which does not contain any jumps. For example, if the input + * is: + * + * (loop (...) ...instrs...) + * + * And the iteration count is 3, the output will be: + * + * ...instrs... ...instrs... ...instrs... + */ +void +loop_unroll_visitor::simple_unroll(ir_loop *ir, int iterations) +{ + void *const mem_ctx = ralloc_parent(ir); + + for (int i = 0; i < iterations; i++) { + exec_list copy_list; + + copy_list.make_empty(); + clone_ir_list(mem_ctx, ©_list, &ir->body_instructions); + + ir->insert_before(©_list); + } + + /* The loop has been replaced by the unrolled copies. Remove the original + * loop from the IR sequence. + */ + ir->remove(); + + this->progress = true; +} + + +/** + * Unroll a loop whose last statement is an ir_if. If \c + * continue_from_then_branch is true, the loop is repeated only when the + * "then" branch of the if is taken; otherwise it is repeated only when the + * "else" branch of the if is taken. + * + * For example, if the input is: + * + * (loop (...) + * ...body... + * (if (cond) + * (...then_instrs...) + * (...else_instrs...))) + * + * And the iteration count is 3, and \c continue_from_then_branch is true, + * then the output will be: + * + * ...body... + * (if (cond) + * (...then_instrs... + * ...body... + * (if (cond) + * (...then_instrs... + * ...body... + * (if (cond) + * (...then_instrs...) + * (...else_instrs...))) + * (...else_instrs...))) + * (...else_instrs)) + */ +void +loop_unroll_visitor::complex_unroll(ir_loop *ir, int iterations, + bool continue_from_then_branch) +{ + void *const mem_ctx = ralloc_parent(ir); + ir_instruction *ir_to_replace = ir; + + for (int i = 0; i < iterations; i++) { + exec_list copy_list; + + copy_list.make_empty(); + clone_ir_list(mem_ctx, ©_list, &ir->body_instructions); + + ir_if *ir_if = ((ir_instruction *) copy_list.get_tail())->as_if(); + assert(ir_if != NULL); + + ir_to_replace->insert_before(©_list); + ir_to_replace->remove(); + + /* placeholder that will be removed in the next iteration */ + ir_to_replace = + new(mem_ctx) ir_loop_jump(ir_loop_jump::jump_continue); + + exec_list *const list = (continue_from_then_branch) + ? &ir_if->then_instructions : &ir_if->else_instructions; + + list->push_tail(ir_to_replace); + } + + ir_to_replace->remove(); + + this->progress = true; +} + + +/** + * Move all of the instructions which follow \c ir_if to the end of + * \c splice_dest. + * + * For example, in the code snippet: + * + * (if (cond) + * (...then_instructions... + * break) + * (...else_instructions...)) + * ...post_if_instructions... + * + * If \c ir_if points to the "if" instruction, and \c splice_dest points to + * (...else_instructions...), the code snippet is transformed into: + * + * (if (cond) + * (...then_instructions... + * break) + * (...else_instructions... + * ...post_if_instructions...)) + */ +void +loop_unroll_visitor::splice_post_if_instructions(ir_if *ir_if, + exec_list *splice_dest) +{ + while (!ir_if->get_next()->is_tail_sentinel()) { + ir_instruction *move_ir = (ir_instruction *) ir_if->get_next(); + + move_ir->remove(); + splice_dest->push_tail(move_ir); + } +} + + ir_visitor_status loop_unroll_visitor::visit_leave(ir_loop *ir) { @@ -100,14 +236,14 @@ loop_unroll_visitor::visit_leave(ir_loop *ir) return visit_continue; } - iterations = ls->max_iterations; - /* Don't try to unroll loops where the number of iterations is not known * at compile-time. */ - if (iterations < 0) + if (ls->limiting_terminator == NULL) return visit_continue; + iterations = ls->limiting_terminator->iterations; + /* Don't try to unroll loops that have zillions of iterations either. */ if (iterations > (int) max_iterations) @@ -120,127 +256,83 @@ loop_unroll_visitor::visit_leave(ir_loop *ir) if (count.fail || count.nodes * iterations > (int)max_iterations * 5) return visit_continue; - if (ls->num_loop_jumps > 1) - return visit_continue; - else if (ls->num_loop_jumps) { - ir_instruction *last_ir = (ir_instruction *) ir->body_instructions.get_tail(); - assert(last_ir != NULL); - - if (is_break(last_ir)) { - /* If the only loop-jump is a break at the end of the loop, the loop - * will execute exactly once. Remove the break, set the iteration - * count, and fall through to the normal unroller. - */ - last_ir->remove(); - iterations = 1; - - this->progress = true; - } else { - ir_if *ir_if = NULL; - ir_instruction *break_ir = NULL; - bool continue_from_then_branch = false; - - foreach_list(node, &ir->body_instructions) { - /* recognize loops in the form produced by ir_lower_jumps */ - ir_instruction *cur_ir = (ir_instruction *) node; - - ir_if = cur_ir->as_if(); - if (ir_if != NULL) { - /* Determine which if-statement branch, if any, ends with a - * break. The branch that did *not* have the break will get a - * temporary continue inserted in each iteration of the loop - * unroll. - * - * Note that since ls->num_loop_jumps is <= 1, it is impossible - * for both branches to end with a break. - */ - ir_instruction *ir_if_last = - (ir_instruction *) ir_if->then_instructions.get_tail(); - - if (is_break(ir_if_last)) { - continue_from_then_branch = false; - break_ir = ir_if_last; - break; - } else { - ir_if_last = - (ir_instruction *) ir_if->else_instructions.get_tail(); - - if (is_break(ir_if_last)) { - break_ir = ir_if_last; - continue_from_then_branch = true; - break; - } - } - } - } - - if (break_ir == NULL) - return visit_continue; - - /* move instructions after then if in the continue branch */ - while (!ir_if->get_next()->is_tail_sentinel()) { - ir_instruction *move_ir = (ir_instruction *) ir_if->get_next(); - - move_ir->remove(); - if (continue_from_then_branch) - ir_if->then_instructions.push_tail(move_ir); - else - ir_if->else_instructions.push_tail(move_ir); - } - - /* Remove the break from the if-statement. - */ - break_ir->remove(); - - void *const mem_ctx = ralloc_parent(ir); - ir_instruction *ir_to_replace = ir; - - for (int i = 0; i < iterations; i++) { - exec_list copy_list; + /* Note: the limiting terminator contributes 1 to ls->num_loop_jumps. + * We'll be removing the limiting terminator before we unroll. + */ + assert(ls->num_loop_jumps > 0); + unsigned predicted_num_loop_jumps = ls->num_loop_jumps - 1; - copy_list.make_empty(); - clone_ir_list(mem_ctx, ©_list, &ir->body_instructions); + if (predicted_num_loop_jumps > 1) + return visit_continue; - ir_if = ((ir_instruction *) copy_list.get_tail())->as_if(); - assert(ir_if != NULL); + if (predicted_num_loop_jumps == 0) { + ls->limiting_terminator->ir->remove(); + simple_unroll(ir, iterations); + return visit_continue; + } - ir_to_replace->insert_before(©_list); - ir_to_replace->remove(); + ir_instruction *last_ir = (ir_instruction *) ir->body_instructions.get_tail(); + assert(last_ir != NULL); - /* placeholder that will be removed in the next iteration */ - ir_to_replace = - new(mem_ctx) ir_loop_jump(ir_loop_jump::jump_continue); + if (is_break(last_ir)) { + /* If the only loop-jump is a break at the end of the loop, the loop + * will execute exactly once. Remove the break and use the simple + * unroller with an iteration count of 1. + */ + last_ir->remove(); - exec_list *const list = (continue_from_then_branch) - ? &ir_if->then_instructions : &ir_if->else_instructions; + ls->limiting_terminator->ir->remove(); + simple_unroll(ir, 1); + return visit_continue; + } - list->push_tail(ir_to_replace); + foreach_list(node, &ir->body_instructions) { + /* recognize loops in the form produced by ir_lower_jumps */ + ir_instruction *cur_ir = (ir_instruction *) node; + + /* Skip the limiting terminator, since it will go away when we + * unroll. + */ + if (cur_ir == ls->limiting_terminator->ir) + continue; + + ir_if *ir_if = cur_ir->as_if(); + if (ir_if != NULL) { + /* Determine which if-statement branch, if any, ends with a + * break. The branch that did *not* have the break will get a + * temporary continue inserted in each iteration of the loop + * unroll. + * + * Note that since ls->num_loop_jumps is <= 1, it is impossible + * for both branches to end with a break. + */ + ir_instruction *ir_if_last = + (ir_instruction *) ir_if->then_instructions.get_tail(); + + if (is_break(ir_if_last)) { + ls->limiting_terminator->ir->remove(); + splice_post_if_instructions(ir_if, &ir_if->else_instructions); + ir_if_last->remove(); + complex_unroll(ir, iterations, false); + return visit_continue; + } else { + ir_if_last = + (ir_instruction *) ir_if->else_instructions.get_tail(); + + if (is_break(ir_if_last)) { + ls->limiting_terminator->ir->remove(); + splice_post_if_instructions(ir_if, &ir_if->then_instructions); + ir_if_last->remove(); + complex_unroll(ir, iterations, true); + return visit_continue; + } } - - ir_to_replace->remove(); - - this->progress = true; - return visit_continue; } } - void *const mem_ctx = ralloc_parent(ir); - - for (int i = 0; i < iterations; i++) { - exec_list copy_list; - - copy_list.make_empty(); - clone_ir_list(mem_ctx, ©_list, &ir->body_instructions); - - ir->insert_before(©_list); - } - - /* The loop has been replaced by the unrolled copies. Remove the original - * loop from the IR sequence. + /* Did not find the break statement. It must be in a complex if-nesting, + * so don't try to unroll. */ - ir->remove(); - - this->progress = true; return visit_continue; } |