From: Ian Romanick <ian.d.roman...@intel.com>
Some shaders end up with code that looks something like:
if (some_condition)
result = 1.0;
else
result = 0.0;
This pass converts those if-statements to
result = float(some_condition);
total instructions in shared programs: 5934568 -> 5921818 (-0.21%)
instructions in affected programs: 723433 -> 710683 (-1.76%)
GAINED: 26
LOST: 7
12 vertex shaders contain loops that we were now able to unroll.
Since their instruction count deltas are not representative of this
change, I've removed them from the stats.
Reviewed-by: Matt Turner <matts...@gmail.com>
---
idr: Want to put an S-o-b on this?
src/glsl/Makefile.sources | 1 +
src/glsl/glsl_parser_extras.cpp | 1 +
src/glsl/ir_optimization.h | 1 +
src/glsl/opt_if_to_bool_cast.cpp | 178 +++++++++++++++++++++++++++++++++++++++
4 files changed, 181 insertions(+)
create mode 100644 src/glsl/opt_if_to_bool_cast.cpp
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 006e947..61de09b 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -162,6 +162,7 @@ LIBGLSL_FILES = \
$(GLSL_SRCDIR)/opt_flip_matrices.cpp \
$(GLSL_SRCDIR)/opt_function_inlining.cpp \
$(GLSL_SRCDIR)/opt_if_simplification.cpp \
+ $(GLSL_SRCDIR)/opt_if_to_bool_cast.cpp \
$(GLSL_SRCDIR)/opt_minmax.cpp \
$(GLSL_SRCDIR)/opt_noop_swizzle.cpp \
$(GLSL_SRCDIR)/opt_rebalance_tree.cpp \
diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
index 6d18cd4..c96b6c9 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -1603,6 +1603,7 @@ do_common_optimization(exec_list *ir, bool linked,
progress = do_structure_splitting(ir) || progress;
}
progress = do_if_simplification(ir) || progress;
+ progress = optimize_if_to_bool_cast(ir) || progress;
progress = opt_flatten_nested_if_blocks(ir) || progress;
progress = do_copy_propagation(ir) || progress;
progress = do_copy_propagation_elements(ir) || progress;
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index 34e0b4b..4dbbd7c 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -131,6 +131,7 @@ void optimize_dead_builtin_variables(exec_list
*instructions,
enum ir_variable_mode other);
bool lower_vertex_id(gl_shader *shader);
+bool optimize_if_to_bool_cast(exec_list *instructions);
ir_rvalue *
compare_index_block(exec_list *instructions, ir_variable *index,
diff --git a/src/glsl/opt_if_to_bool_cast.cpp b/src/glsl/opt_if_to_bool_cast.cpp
new file mode 100644
index 0000000..32c1f99
--- /dev/null
+++ b/src/glsl/opt_if_to_bool_cast.cpp
@@ -0,0 +1,178 @@
+/*
+ * Copyright © 2014 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_if_to_bool_cast.cpp
+ * Optimize certain if-statements to just casts from the condition
+ *
+ * Some shaders end up with code that looks something like:
+ *
+ * if (some_condition)
+ * result = 1.0;
+ * else
+ * result = 0.0;
+ *
+ * This pass converts those if-statements to
+ *
+ * result = float(some_condition);
+ */
+
+#include "main/imports.h"
+#include "ir.h"
+#include "ir_builder.h"
+#include "program/prog_instruction.h"
+
+using namespace ir_builder;
+
+namespace {
+
+class ir_if_to_bool_cast_visitor : public ir_hierarchical_visitor {
+public:
+ ir_if_to_bool_cast_visitor()
+ : progress(false)
+ {
+ /* empty */
+ }
+
+ ir_visitor_status visit_leave(ir_if *);
+
+ bool progress;
+};
+
+} /* unnamed namespace */
+
+bool
+optimize_if_to_bool_cast(exec_list *instructions)
+{
+ ir_if_to_bool_cast_visitor v;
+
+ v.run(instructions);
+ return v.progress;
+}
+
+ir_visitor_status
+ir_if_to_bool_cast_visitor::visit_leave(ir_if *ir)
+{
+ /* Both the then-block and the else-block must contain a single instruction
+ * that is an assignment.
+ */
+ ir_instruction *const then_inst =
+ (ir_instruction *) ir->then_instructions.get_head();
+ if (then_inst == NULL
+ || !then_inst->next->is_tail_sentinel()
+ || then_inst->ir_type != ir_type_assignment)
+ return visit_continue;
+
+ ir_instruction *const else_inst =
+ (ir_instruction *) ir->else_instructions.get_head();
+ if (else_inst == NULL
+ || !else_inst->next->is_tail_sentinel()
+ || else_inst->ir_type != ir_type_assignment)
+ return visit_continue;
+
+ /* That assignment must have the same write-mask and have the same LHS.
+ */
+ ir_assignment *const then_assign = then_inst->as_assignment();
+ ir_assignment *const else_assign = else_inst->as_assignment();
+
+ assert(then_assign != NULL);
+ assert(else_assign != NULL);
+
+ if (then_assign->write_mask != else_assign->write_mask
+ || then_assign->condition != NULL
+ || else_assign->condition != NULL)
+ return visit_continue;
+
+ if (!then_assign->lhs->equals(else_assign->lhs))
+ return visit_continue;
+
+ /* The RHS of the then-assignment must be 1, and the RHS of the
+ * else-assignment must be 0. Or vice-versa.
+ */
+ ir_constant *const then_rhs = then_assign->rhs->as_constant();
+ ir_constant *const else_rhs = else_assign->rhs->as_constant();
+
+ if (then_rhs == NULL || else_rhs == NULL)
+ return visit_continue;
+
+ if (then_rhs->is_zero()) {
+ if (!else_rhs->is_one() && !else_rhs->is_negative_one())
+ return visit_continue;
+ } else if (else_rhs->is_zero()) {
+ if (!then_rhs->is_one() && !then_rhs->is_negative_one())
+ return visit_continue;
+ } else {
+ return visit_continue;
+ }
+
+ /* Generate the RHS of the new assignment. Note that if the old code
+ * looked like
+ *
+ * x = (cond) ? 0.0 : 1.0;
+ *
+ * we have to generate
+ *
+ * x = float(!cond);
+ */
+ ir_rvalue *const cond = then_rhs->is_zero()
+ ? logic_not(ir->condition) : ir->condition;
+
+ ir_rvalue *rhs = NULL;
+
+ switch (then_rhs->type->base_type) {
+ case GLSL_TYPE_UINT:
+ rhs = i2u(b2i(cond));
+ break;
+ case GLSL_TYPE_INT:
+ rhs = b2i(cond);
+ break;
+ case GLSL_TYPE_FLOAT:
+ rhs = b2f(cond);
+ break;
+ case GLSL_TYPE_BOOL:
+ rhs = cond;
+ break;
+ default:
+ unreachable("invalid base type");
+ }
+
+ /* If the non-zero value was -1, negate the result of the b2[uif]
+ * operation.
+ */
+ if (then_rhs->is_negative_one() || else_rhs->is_negative_one())
+ rhs = neg(rhs);
+
+ const unsigned size = _mesa_bitcount(then_assign->write_mask);
+
+ assert(size >= 1 && size <= 4);
+
+ ir_assignment *const a = assign(then_assign->lhs,
+ swizzle(rhs, SWIZZLE_XXXX, size),
+ then_assign->write_mask);
+
+ ir->insert_before(a);
+ ir->remove();
+ progress = true;
+
+ return visit_continue;
+ }
--
2.0.4
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