diff options
Diffstat (limited to 'mesalib/src/glsl/opt_discard_simplification.cpp')
| -rw-r--r-- | mesalib/src/glsl/opt_discard_simplification.cpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/mesalib/src/glsl/opt_discard_simplification.cpp b/mesalib/src/glsl/opt_discard_simplification.cpp new file mode 100644 index 000000000..df8caba4d --- /dev/null +++ b/mesalib/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;
+}
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