From: Ian Romanick <ian.d.roman...@intel.com>
Some shaders end up with code that looks something like:
if (condition)
result = 1.0;
else
result = 0.0;
This pass converts those if-statements to
result = float(condition);
Of the shaders hurt, 12 of them are vertex shaders "hurt" by virtue of
having a loop unrolled.
Shader-db results:
GM45 (0x2A42):
total instructions in shared programs: 3550788 -> 3548093 (-0.08%)
instructions in affected programs: 231205 -> 228510 (-1.17%)
helped: 712
HURT: 43
Iron Lake (0x0046):
total instructions in shared programs: 4980593 -> 4977700 (-0.06%)
instructions in affected programs: 267985 -> 265092 (-1.08%)
helped: 852
HURT: 56
GAINED: 3
LOST: 24
Sandy Bridge (0x0116):
total instructions in shared programs: 6817050 -> 6806224 (-0.16%)
instructions in affected programs: 696386 -> 685560 (-1.55%)
helped: 2510
HURT: 34
GAINED: 1
LOST: 11
Sandy Bridge (0x0116) NIR:
total instructions in shared programs: 6823377 -> 6813527 (-0.14%)
instructions in affected programs: 703053 -> 693203 (-1.40%)
helped: 2555
HURT: 52
LOST: 23
Ivy Bridge (0x0166):
total instructions in shared programs: 6289987 -> 6282273 (-0.12%)
instructions in affected programs: 542999 -> 535285 (-1.42%)
helped: 1751
HURT: 603
GAINED: 1
LOST: 3
Ivy Bridge (0x0166) NIR:
total instructions in shared programs: 6310434 -> 6303918 (-0.10%)
instructions in affected programs: 592493 -> 585977 (-1.10%)
helped: 1874
HURT: 665
GAINED: 21
Haswell (0x0426):
total instructions in shared programs: 5777713 -> 5766346 (-0.20%)
instructions in affected programs: 545464 -> 534097 (-2.08%)
helped: 2314
HURT: 32
GAINED: 1
LOST: 3
Haswell (0x0426) NIR:
total instructions in shared programs: 5791071 -> 5780761 (-0.18%)
instructions in affected programs: 565597 -> 555287 (-1.82%)
helped: 2399
HURT: 52
GAINED: 21
Broadwell (0x162E):
total instructions in shared programs: 6821371 -> 6813617 (-0.11%)
instructions in affected programs: 572656 -> 564902 (-1.35%)
helped: 2316
HURT: 28
GAINED: 2
LOST: 3
Broadwell (0x162E) NIR:
total instructions in shared programs: 7013739 -> 7006622 (-0.10%)
instructions in affected programs: 594449 -> 587332 (-1.20%)
helped: 2396
HURT: 46
Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
---
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 | 184 +++++++++++++++++++++++++++++++++++++++
4 files changed, 187 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 b876642..f49fc86 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -173,6 +173,7 @@ LIBGLSL_FILES = \
opt_flip_matrices.cpp \
opt_function_inlining.cpp \
opt_if_simplification.cpp \
+ opt_if_to_bool_cast.cpp \
opt_minmax.cpp \
opt_noop_swizzle.cpp \
opt_rebalance_tree.cpp \
diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
index 79624bc..cb7ec2b 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -1626,6 +1626,7 @@ 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 = opt_conditional_discard(ir) || progress;
progress = do_copy_propagation(ir) || progress;
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index e6939f3..4892a1d3 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -134,6 +134,7 @@ 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..20a27e3
--- /dev/null
+++ b/src/glsl/opt_if_to_bool_cast.cpp
@@ -0,0 +1,184 @@
+/*
+ * 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;
+}
+
+static ir_assignment *
+emit_0_or_1_assigment(ir_dereference *lhs, unsigned write_mask,
+ ir_rvalue *condition,
+ ir_rvalue *then_rhs, ir_rvalue *else_rhs)
+{
+ /* 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);
+ */
+ if (then_rhs->is_zero())
+ condition = logic_not(condition);
+
+ ir_rvalue *rhs = NULL;
+
+ switch (then_rhs->type->base_type) {
+ case GLSL_TYPE_UINT:
+ rhs = i2u(b2i(condition));
+ break;
+ case GLSL_TYPE_INT:
+ rhs = b2i(condition);
+ break;
+ case GLSL_TYPE_FLOAT:
+ rhs = b2f(condition);
+ break;
+ case GLSL_TYPE_BOOL:
+ rhs = condition;
+ 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(write_mask);
+
+ assert(size >= 1 && size <= 4);
+
+ return assign(lhs, swizzle(rhs, SWIZZLE_XXXX, size), write_mask);
+}
+
+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;
+
+ ir_assignment *a = NULL;
+ if ((then_rhs->is_zero()
+ && (else_rhs->is_one() || else_rhs->is_negative_one()))
+ || (else_rhs->is_zero()
+ && (then_rhs->is_one() || then_rhs->is_negative_one()))) {
+ a = emit_0_or_1_assigment(then_assign->lhs, then_assign->write_mask,
+ ir->condition,
+ then_rhs, else_rhs);
+ }
+
+ if (a != NULL) {
+ ir->insert_before(a);
+ ir->remove();
+ progress = true;
+ }
+
+ return visit_continue;
+ }
--
2.1.0
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