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Diffstat (limited to 'src/glsl/opt_discard_simplification.cpp')
| -rw-r--r-- | src/glsl/opt_discard_simplification.cpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/src/glsl/opt_discard_simplification.cpp b/src/glsl/opt_discard_simplification.cpp new file mode 100644 index 0000000000..0e577c478a --- /dev/null +++ b/src/glsl/opt_discard_simplification.cpp @@ -0,0 +1,180 @@ +/* + * 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. + */ + +/** + * \file opt_discard_simplification.cpp + * + * This pass simplifies if-statements and loops containing unconditional + * discards. + * + * Case 1: Both branches contain unconditional discards: + * ----------------------------------------------------- + * + * if (cond) { + * s1; + * discard; + * s2; + * } else { + * s3; + * discard; + * s4; + * } + * + * becomes: + * + * discard + * + * Case 2: The "then" clause contains an unconditional discard: + * ------------------------------------------------------------ + * + * if (cond) { + * s1; + * discard; + * s2; + * } else { + * s3; + * } + * + * becomes: + * + * if (cond) { + * discard; + * } else { + * s3; + * } + * + * Case 3: The "else" clause contains an unconditional discard: + * ------------------------------------------------------------ + * + * if (cond) { + * s1; + * } else { + * s2; + * discard; + * s3; + * } + * + * becomes: + * + * if (cond) { + * s1; + * } else { + * discard; + * } + */ + +#include "glsl_types.h" +#include "ir.h" + +class discard_simplifier : public ir_hierarchical_visitor { +public: + discard_simplifier() + { + this->progress = false; + } + + ir_visitor_status visit_enter(ir_if *); + ir_visitor_status visit_enter(ir_loop *); + + bool progress; +}; + +static ir_discard * +find_unconditional_discard(exec_list &instructions) +{ + foreach_list(n, &instructions) { + ir_discard *ir = ((ir_instruction *) n)->as_discard(); + if (ir != NULL && ir->condition == NULL) + return ir; + } + return NULL; +} + +static bool +is_only_instruction(ir_discard *discard) +{ + return (discard->prev->is_head_sentinel() && + discard->next->is_tail_sentinel()); +} + +ir_visitor_status +discard_simplifier::visit_enter(ir_if *ir) +{ + ir_discard *then_discard = find_unconditional_discard(ir->then_instructions); + ir_discard *else_discard = find_unconditional_discard(ir->else_instructions); + + if (then_discard == NULL && else_discard == NULL) + return visit_continue; + + /* If both branches result in discard, replace whole if with discard. */ + if (then_discard != NULL && else_discard != NULL) { + this->progress = true; + ir->replace_with(then_discard); + return visit_continue_with_parent; + } + + /* Otherwise, one branch has a discard. */ + if (then_discard != NULL && !is_only_instruction(then_discard)) { + this->progress = true; + ir->then_instructions.make_empty(); + ir->then_instructions.push_tail(then_discard); + } else if (else_discard != NULL && !is_only_instruction(else_discard)) { + this->progress = true; + ir->else_instructions.make_empty(); + ir->else_instructions.push_tail(else_discard); + } + + visit_list_elements(this, &ir->then_instructions); + return visit_continue_with_parent; +} + +ir_visitor_status +discard_simplifier::visit_enter(ir_loop *ir) +{ + ir_discard *discard = find_unconditional_discard(ir->body_instructions); + + if (discard) { + ir->replace_with(discard); + return visit_continue_with_parent; + } + + return visit_continue; +} + +bool +do_discard_simplification(exec_list *instructions) +{ + /* Look for a top-level unconditional discard */ + ir_discard *discard = find_unconditional_discard(*instructions); + if (discard != NULL) { + instructions->make_empty(); + instructions->push_tail(discard); + return true; + } + + discard_simplifier v; + + visit_list_elements(&v, instructions); + + return v.progress; +} |