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Diffstat (limited to 'src/compiler/glsl/loop_unroll.cpp')
| -rw-r--r-- | src/compiler/glsl/loop_unroll.cpp | 432 |
1 files changed, 432 insertions, 0 deletions
diff --git a/src/compiler/glsl/loop_unroll.cpp b/src/compiler/glsl/loop_unroll.cpp new file mode 100644 index 00000000000..aea2743cdb1 --- /dev/null +++ b/src/compiler/glsl/loop_unroll.cpp @@ -0,0 +1,432 @@ +/* + * Copyright © 2010 Intel Corporation + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER + * DEALINGS IN THE SOFTWARE. + */ + +#include "compiler/glsl_types.h" +#include "loop_analysis.h" +#include "ir_hierarchical_visitor.h" + +#include "main/mtypes.h" + +namespace { + +class loop_unroll_visitor : public ir_hierarchical_visitor { +public: + loop_unroll_visitor(loop_state *state, + const struct gl_shader_compiler_options *options) + { + this->state = state; + this->progress = false; + this->options = options; + } + + 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; + + bool progress; + const struct gl_shader_compiler_options *options; +}; + +} /* anonymous namespace */ + +static bool +is_break(ir_instruction *ir) +{ + return ir != NULL && ir->ir_type == ir_type_loop_jump + && ((ir_loop_jump *) ir)->is_break(); +} + +class loop_unroll_count : public ir_hierarchical_visitor { +public: + int nodes; + bool unsupported_variable_indexing; + bool array_indexed_by_induction_var_with_exact_iterations; + /* If there are nested loops, the node count will be inaccurate. */ + bool nested_loop; + + loop_unroll_count(exec_list *list, loop_variable_state *ls, + const struct gl_shader_compiler_options *options) + : ls(ls), options(options) + { + nodes = 0; + nested_loop = false; + unsupported_variable_indexing = false; + array_indexed_by_induction_var_with_exact_iterations = false; + + run(list); + } + + virtual ir_visitor_status visit_enter(ir_assignment *) + { + nodes++; + return visit_continue; + } + + virtual ir_visitor_status visit_enter(ir_expression *) + { + nodes++; + return visit_continue; + } + + virtual ir_visitor_status visit_enter(ir_loop *) + { + nested_loop = true; + return visit_continue; + } + + virtual ir_visitor_status visit_enter(ir_dereference_array *ir) + { + /* Force unroll in case of dynamic indexing with sampler arrays + * when EmitNoIndirectSampler is set. + */ + if (options->EmitNoIndirectSampler) { + if ((ir->array->type->is_array() && + ir->array->type->contains_sampler()) && + !ir->array_index->constant_expression_value()) { + unsupported_variable_indexing = true; + return visit_continue; + } + } + + /* Check for arrays variably-indexed by a loop induction variable. + * Unrolling the loop may convert that access into constant-indexing. + * + * Many drivers don't support particular kinds of variable indexing, + * and have to resort to using lower_variable_index_to_cond_assign to + * handle it. This results in huge amounts of horrible code, so we'd + * like to avoid that if possible. Here, we just note that it will + * happen. + */ + if ((ir->array->type->is_array() || ir->array->type->is_matrix()) && + !ir->array_index->as_constant()) { + ir_variable *array = ir->array->variable_referenced(); + loop_variable *lv = ls->get(ir->array_index->variable_referenced()); + if (array && lv && lv->is_induction_var()) { + /* If an array is indexed by a loop induction variable, and the + * array size is exactly the number of loop iterations, this is + * probably a simple for-loop trying to access each element in + * turn; the application may expect it to be unrolled. + */ + if (int(array->type->length) == ls->limiting_terminator->iterations) + array_indexed_by_induction_var_with_exact_iterations = true; + + switch (array->data.mode) { + case ir_var_auto: + case ir_var_temporary: + case ir_var_const_in: + case ir_var_function_in: + case ir_var_function_out: + case ir_var_function_inout: + if (options->EmitNoIndirectTemp) + unsupported_variable_indexing = true; + break; + case ir_var_uniform: + case ir_var_shader_storage: + if (options->EmitNoIndirectUniform) + unsupported_variable_indexing = true; + break; + case ir_var_shader_in: + if (options->EmitNoIndirectInput) + unsupported_variable_indexing = true; + break; + case ir_var_shader_out: + if (options->EmitNoIndirectOutput) + unsupported_variable_indexing = true; + break; + } + } + } + return visit_continue; + } + +private: + loop_variable_state *ls; + const struct gl_shader_compiler_options *options; +}; + + +/** + * 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) +{ + loop_variable_state *const ls = this->state->get(ir); + int iterations; + + /* If we've entered a loop that hasn't been analyzed, something really, + * really bad has happened. + */ + if (ls == NULL) { + assert(ls != NULL); + return visit_continue; + } + + /* Don't try to unroll loops where the number of iterations is not known + * at compile-time. + */ + if (ls->limiting_terminator == NULL) + return visit_continue; + + iterations = ls->limiting_terminator->iterations; + + const int max_iterations = options->MaxUnrollIterations; + + /* Don't try to unroll loops that have zillions of iterations either. + */ + if (iterations > max_iterations) + return visit_continue; + + /* Don't try to unroll nested loops and loops with a huge body. + */ + loop_unroll_count count(&ir->body_instructions, ls, options); + + bool loop_too_large = + count.nested_loop || count.nodes * iterations > max_iterations * 5; + + if (loop_too_large && !count.unsupported_variable_indexing && + !count.array_indexed_by_induction_var_with_exact_iterations) + return visit_continue; + + /* 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; + + if (predicted_num_loop_jumps > 1) + return visit_continue; + + if (predicted_num_loop_jumps == 0) { + ls->limiting_terminator->ir->remove(); + simple_unroll(ir, iterations); + return visit_continue; + } + + 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 and use the simple + * unroller with an iteration count of 1. + */ + last_ir->remove(); + + ls->limiting_terminator->ir->remove(); + simple_unroll(ir, 1); + return visit_continue; + } + + /* recognize loops in the form produced by ir_lower_jumps */ + foreach_in_list(ir_instruction, cur_ir, &ir->body_instructions) { + /* 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; + } + } + } + } + + /* Did not find the break statement. It must be in a complex if-nesting, + * so don't try to unroll. + */ + return visit_continue; +} + + +bool +unroll_loops(exec_list *instructions, loop_state *ls, + const struct gl_shader_compiler_options *options) +{ + loop_unroll_visitor v(ls, options); + + v.run(instructions); + + return v.progress; +} |