WebSVN – Kolibri OS – Blame – /programs/develop/libraries/Mesa/src/glsl/lower_discard.cpp

Rev	Author	Line No.	Line
1901	serge	1	/*
		2	* Copyright © 2010 Intel Corporation
		3	*
		4	* Permission is hereby granted, free of charge, to any person obtaining a
		5	* copy of this software and associated documentation files (the "Software"),
		6	* to deal in the Software without restriction, including without limitation
		7	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
		8	* and/or sell copies of the Software, and to permit persons to whom the
		9	* Software is furnished to do so, subject to the following conditions:
		10	*
		11	* The above copyright notice and this permission notice (including the next
		12	* paragraph) shall be included in all copies or substantial portions of the
		13	* Software.
		14	*
		15	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
		16	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
		17	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
		18	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
		19	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
		20	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
		21	* DEALINGS IN THE SOFTWARE.
		22	*/
		23
		24	/**
		25	* \file lower_discard.cpp
		26	*
		27	* This pass moves discards out of if-statements.
		28	*
		29	* Case 1: The "then" branch contains a conditional discard:
		30	* ---------------------------------------------------------
		31	*
		32	* if (cond1) {
		33	* s1;
		34	* discard cond2;
		35	* s2;
		36	* } else {
		37	* s3;
		38	* }
		39	*
		40	* becomes:
		41	*
		42	* temp = false;
		43	* if (cond1) {
		44	* s1;
		45	* temp = cond2;
		46	* s2;
		47	* } else {
		48	* s3;
		49	* }
		50	* discard temp;
		51	*
		52	* Case 2: The "else" branch contains a conditional discard:
		53	* ---------------------------------------------------------
		54	*
		55	* if (cond1) {
		56	* s1;
		57	* } else {
		58	* s2;
		59	* discard cond2;
		60	* s3;
		61	* }
		62	*
		63	* becomes:
		64	*
		65	* temp = false;
		66	* if (cond1) {
		67	* s1;
		68	* } else {
		69	* s2;
		70	* temp = cond2;
		71	* s3;
		72	* }
		73	* discard temp;
		74	*
		75	* Case 3: Both branches contain a conditional discard:
		76	* ----------------------------------------------------
		77	*
		78	* if (cond1) {
		79	* s1;
		80	* discard cond2;
		81	* s2;
		82	* } else {
		83	* s3;
		84	* discard cond3;
		85	* s4;
		86	* }
		87	*
		88	* becomes:
		89	*
		90	* temp = false;
		91	* if (cond1) {
		92	* s1;
		93	* temp = cond2;
		94	* s2;
		95	* } else {
		96	* s3;
		97	* temp = cond3;
		98	* s4;
		99	* }
		100	* discard temp;
		101	*
		102	* If there are multiple conditional discards, we need only deal with one of
		103	* them. Repeatedly applying this pass will take care of the others.
		104	*
		105	* Unconditional discards are treated as having a condition of "true".
		106	*/
		107
		108	#include "glsl_types.h"
		109	#include "ir.h"
		110
		111	class lower_discard_visitor : public ir_hierarchical_visitor {
		112	public:
		113	lower_discard_visitor()
		114	{
		115	this->progress = false;
		116	}
		117
		118	ir_visitor_status visit_leave(ir_if *);
		119
		120	bool progress;
		121	};
		122
		123
		124	bool
		125	lower_discard(exec_list *instructions)
		126	{
		127	lower_discard_visitor v;
		128
		129	visit_list_elements(&v, instructions);
		130
		131	return v.progress;
		132	}
		133
		134
		135	static ir_discard *
		136	find_discard(exec_list &instructions)
		137	{
		138	foreach_list(n, &instructions) {
		139	ir_discard ir = ((ir_instruction ) n)->as_discard();
		140	if (ir != NULL)
		141	return ir;
		142	}
		143	return NULL;
		144	}
		145
		146
		147	static void
		148	replace_discard(void mem_ctx, ir_variable var, ir_discard *ir)
		149	{
		150	ir_rvalue *condition = ir->condition;
		151
		152	/* For unconditional discards, use "true" as the condition. */
		153	if (condition == NULL)
		154	condition = new(mem_ctx) ir_constant(true);
		155
		156	ir_assignment *assignment =
		157	new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(var),
		158	condition, NULL);
		159
		160	ir->replace_with(assignment);
		161	}
		162
		163
		164	ir_visitor_status
		165	lower_discard_visitor::visit_leave(ir_if *ir)
		166	{
		167	ir_discard *then_discard = find_discard(ir->then_instructions);
		168	ir_discard *else_discard = find_discard(ir->else_instructions);
		169
		170	if (then_discard == NULL && else_discard == NULL)
		171	return visit_continue;
		172
		173	void *mem_ctx = ralloc_parent(ir);
		174
		175	ir_variable *temp = new(mem_ctx) ir_variable(glsl_type::bool_type,
		176	"discard_cond_temp",
		177	ir_var_temporary);
		178	ir_assignment *temp_initializer =
		179	new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(temp),
		180	new(mem_ctx) ir_constant(false), NULL);
		181
		182	ir->insert_before(temp);
		183	ir->insert_before(temp_initializer);
		184
		185	if (then_discard != NULL)
		186	replace_discard(mem_ctx, temp, then_discard);
		187
		188	if (else_discard != NULL)
		189	replace_discard(mem_ctx, temp, else_discard);
		190
		191	ir_discard *discard = then_discard != NULL ? then_discard : else_discard;
		192	discard->condition = new(mem_ctx) ir_dereference_variable(temp);
		193	ir->insert_after(discard);
		194
		195	this->progress = true;
		196
		197	return visit_continue;
		198	}

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