[Mesa-dev] [PATCH 1/3] glsl: Add an optimization pass to simplify discards.
Kenneth Graunke
kenneth at whitecape.org
Thu Nov 25 03:40:23 PST 2010
Fixes bug #31690. The unconditional discard inside the if-statement is
now turned into a conditional discard.
NOTE: This is a candidate for the 7.9 branch.
---
src/glsl/Makefile | 1 +
src/glsl/SConscript | 1 +
src/glsl/glsl_parser_extras.cpp | 1 +
src/glsl/ir_optimization.h | 1 +
src/glsl/opt_discard_simplification.cpp | 201 +++++++++++++++++++++++++++++++
5 files changed, 205 insertions(+), 0 deletions(-)
create mode 100644 src/glsl/opt_discard_simplification.cpp
diff --git a/src/glsl/Makefile b/src/glsl/Makefile
index f5aadc3..83ecb7f 100644
--- a/src/glsl/Makefile
+++ b/src/glsl/Makefile
@@ -70,6 +70,7 @@ CXX_SOURCES = \
opt_dead_code.cpp \
opt_dead_code_local.cpp \
opt_dead_functions.cpp \
+ opt_discard_simplification.cpp \
opt_function_inlining.cpp \
opt_if_simplification.cpp \
opt_noop_swizzle.cpp \
diff --git a/src/glsl/SConscript b/src/glsl/SConscript
index fd22f66..16f02e9 100644
--- a/src/glsl/SConscript
+++ b/src/glsl/SConscript
@@ -66,6 +66,7 @@ sources = [
'opt_dead_code.cpp',
'opt_dead_code_local.cpp',
'opt_dead_functions.cpp',
+ 'opt_discard_simplification.cpp',
'opt_function_inlining.cpp',
'opt_if_simplification.cpp',
'opt_noop_swizzle.cpp',
diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
index 302cfbc..8dbe669 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -716,6 +716,7 @@ do_common_optimization(exec_list *ir, bool linked, unsigned max_unroll_iteration
}
progress = do_structure_splitting(ir) || progress;
progress = do_if_simplification(ir) || progress;
+ progress = do_discard_simplification(ir) || progress;
progress = do_copy_propagation(ir) || progress;
if (linked)
progress = do_dead_code(ir) || progress;
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index fa497a4..05c1bec 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -51,6 +51,7 @@ bool do_function_inlining(exec_list *instructions);
bool do_lower_jumps(exec_list *instructions, bool pull_out_jumps = true, bool lower_sub_return = true, bool lower_main_return = false, bool lower_continue = false, bool lower_break = false);
bool do_lower_texture_projection(exec_list *instructions);
bool do_if_simplification(exec_list *instructions);
+bool do_discard_simplification(exec_list *instructions);
bool do_if_to_cond_assign(exec_list *instructions);
bool do_mat_op_to_vec(exec_list *instructions);
bool do_mod_to_fract(exec_list *instructions);
diff --git a/src/glsl/opt_discard_simplification.cpp b/src/glsl/opt_discard_simplification.cpp
new file mode 100644
index 0000000..ac92e8f
--- /dev/null
+++ b/src/glsl/opt_discard_simplification.cpp
@@ -0,0 +1,201 @@
+/*
+ * 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:
+ *
+ * temp = cond;
+ * discard temp;
+ * if (!temp) {
+ * s3;
+ * }
+ *
+ * Case 3: The "else" clause contains an unconditional discard:
+ * ------------------------------------------------------------
+ *
+ * if (cond) {
+ * s1
+ * } else {
+ * s2
+ * discard;
+ * s3
+ * }
+ *
+ * becomes:
+ *
+ * temp = cond;
+ * discard !temp;
+ * if (temp) {
+ * s1;
+ * }
+ */
+
+#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 ir_variable *
+cond_to_temp(void *mem_ctx, ir_if *ir)
+{
+ ir_variable *var = new(mem_ctx) ir_variable(ir->condition->type, "cond_temp",
+ ir_var_temporary);
+ ir_assignment *assignment =
+ new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(var),
+ ir->condition->clone(mem_ctx, NULL),
+ NULL);
+
+ ir->insert_before(var);
+ ir->insert_before(assignment);
+ return var;
+}
+
+ir_visitor_status
+discard_simplifier::visit_enter(ir_if *ir)
+{
+ void *mem_ctx = talloc_parent(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;
+
+ this->progress = true;
+
+ /* If both branches result in discard, replace whole if with discard. */
+ if (then_discard != NULL && else_discard != NULL) {
+ ir->replace_with(then_discard);
+ return visit_continue_with_parent;
+ }
+
+ /* Otherwise, one branch has a discard. */
+ ir_variable *temp = cond_to_temp(mem_ctx, ir);
+ ir_rvalue *cond = new(mem_ctx) ir_dereference_variable(temp);
+ ir_rvalue *not_cond =
+ new(mem_ctx) ir_expression(ir_unop_logic_not, cond->type,
+ new(mem_ctx) ir_dereference_variable(temp));
+
+ if (then_discard != NULL) {
+ ir->condition = not_cond;
+ ir->else_instructions.move_nodes_to(&ir->then_instructions);
+
+ then_discard->condition = cond;
+ ir->insert_before(then_discard);
+ } else {
+ ir->condition = cond;
+ ir->else_instructions.make_empty();
+
+ else_discard->condition = not_cond;
+ ir->insert_before(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;
+}
--
1.7.3.2
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