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Diffstat (limited to 'src/glsl/lower_discard.cpp')
| -rw-r--r-- | src/glsl/lower_discard.cpp | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/src/glsl/lower_discard.cpp b/src/glsl/lower_discard.cpp new file mode 100644 index 0000000000..b95313df8c --- /dev/null +++ b/src/glsl/lower_discard.cpp @@ -0,0 +1,198 @@ +/* + * 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 lower_discard.cpp + * + * This pass moves discards out of if-statements. + * + * Case 1: The "then" branch contains a conditional discard: + * --------------------------------------------------------- + * + * if (cond1) { + * s1; + * discard cond2; + * s2; + * } else { + * s3; + * } + * + * becomes: + * + * temp = false; + * if (cond1) { + * s1; + * temp = cond2; + * s2; + * } else { + * s3; + * } + * discard temp; + * + * Case 2: The "else" branch contains a conditional discard: + * --------------------------------------------------------- + * + * if (cond1) { + * s1; + * } else { + * s2; + * discard cond2; + * s3; + * } + * + * becomes: + * + * temp = false; + * if (cond1) { + * s1; + * } else { + * s2; + * temp = cond2; + * s3; + * } + * discard temp; + * + * Case 3: Both branches contain a conditional discard: + * ---------------------------------------------------- + * + * if (cond1) { + * s1; + * discard cond2; + * s2; + * } else { + * s3; + * discard cond3; + * s4; + * } + * + * becomes: + * + * temp = false; + * if (cond1) { + * s1; + * temp = cond2; + * s2; + * } else { + * s3; + * temp = cond3; + * s4; + * } + * discard temp; + * + * If there are multiple conditional discards, we need only deal with one of + * them. Repeatedly applying this pass will take care of the others. + * + * Unconditional discards are treated as having a condition of "true". + */ + +#include "glsl_types.h" +#include "ir.h" + +class lower_discard_visitor : public ir_hierarchical_visitor { +public: + lower_discard_visitor() + { + this->progress = false; + } + + ir_visitor_status visit_leave(ir_if *); + + bool progress; +}; + + +bool +lower_discard(exec_list *instructions) +{ + lower_discard_visitor v; + + visit_list_elements(&v, instructions); + + return v.progress; +} + + +static ir_discard * +find_discard(exec_list &instructions) +{ + foreach_list(n, &instructions) { + ir_discard *ir = ((ir_instruction *) n)->as_discard(); + if (ir != NULL) + return ir; + } + return NULL; +} + + +static void +replace_discard(void *mem_ctx, ir_variable *var, ir_discard *ir) +{ + ir_rvalue *condition = ir->condition; + + /* For unconditional discards, use "true" as the condition. */ + if (condition == NULL) + condition = new(mem_ctx) ir_constant(true); + + ir_assignment *assignment = + new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(var), + condition, NULL); + + ir->replace_with(assignment); +} + + +ir_visitor_status +lower_discard_visitor::visit_leave(ir_if *ir) +{ + ir_discard *then_discard = find_discard(ir->then_instructions); + ir_discard *else_discard = find_discard(ir->else_instructions); + + if (then_discard == NULL && else_discard == NULL) + return visit_continue; + + void *mem_ctx = talloc_parent(ir); + + ir_variable *temp = new(mem_ctx) ir_variable(glsl_type::bool_type, + "discard_cond_temp", + ir_var_temporary); + ir_assignment *temp_initializer = + new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(temp), + new(mem_ctx) ir_constant(false), NULL); + + ir->insert_before(temp); + ir->insert_before(temp_initializer); + + if (then_discard != NULL) + replace_discard(mem_ctx, temp, then_discard); + + if (else_discard != NULL) + replace_discard(mem_ctx, temp, else_discard); + + ir_discard *discard = then_discard != NULL ? then_discard : else_discard; + discard->condition = new(mem_ctx) ir_dereference_variable(temp); + ir->insert_after(discard); + + this->progress = true; + + return visit_continue; +} |