[Mesa-dev] [PATCH 1/9] glsl: Optimize min/max expression trees
Petri Latvala
petri.latvala at intel.com
Tue Jul 29 02:36:31 PDT 2014
Add an optimization pass that drops min/max expression operands that
can be proven to not contribute to the final result. The algorithm is
similar to alpha-beta pruning on a minmax search, from the field of
AI.
This optimization pass can optimize min/max expressions where operands
are min/max expressions. Such code can appear in shaders by itself, or
as the result of clamp() or AMD_shader_trinary_minmax functions.
This optimization pass improves the generated code for piglit's
AMD_shader_trinary_minmax tests as follows:
total instructions in shared programs: 75 -> 67 (-10.67%)
instructions in affected programs: 60 -> 52 (-13.33%)
GAINED: 0
LOST: 0
All tests (max3, min3, mid3) improved.
A full shader-db run:
total instructions in shared programs: 4293603 -> 4293575 (-0.00%)
instructions in affected programs: 1188 -> 1160 (-2.36%)
GAINED: 0
LOST: 0
Improvements happen in Guacamelee and Serious Sam 3. One shader from
Dungeon Defenders is hurt by shader-db metrics (26 -> 28), because of
dropping of a (constant float (0.00000)) operand, which was
compiled to a saturate modifier.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76861
Signed-off-by: Petri Latvala <petri.latvala at intel.com>
---
src/glsl/Makefile.sources | 1 +
src/glsl/glsl_parser_extras.cpp | 1 +
src/glsl/ir_optimization.h | 1 +
src/glsl/opt_minmax.cpp | 395 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 398 insertions(+)
create mode 100644 src/glsl/opt_minmax.cpp
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index b54eae7..1ee80a3 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -95,6 +95,7 @@ LIBGLSL_FILES = \
$(GLSL_SRCDIR)/opt_flip_matrices.cpp \
$(GLSL_SRCDIR)/opt_function_inlining.cpp \
$(GLSL_SRCDIR)/opt_if_simplification.cpp \
+ $(GLSL_SRCDIR)/opt_minmax.cpp \
$(GLSL_SRCDIR)/opt_noop_swizzle.cpp \
$(GLSL_SRCDIR)/opt_rebalance_tree.cpp \
$(GLSL_SRCDIR)/opt_redundant_jumps.cpp \
diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
index 890123a..9f57ef3 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -1561,6 +1561,7 @@ do_common_optimization(exec_list *ir, bool linked,
else
progress = do_constant_variable_unlinked(ir) || progress;
progress = do_constant_folding(ir) || progress;
+ progress = do_minmax_prune(ir) || progress;
progress = do_cse(ir) || progress;
progress = do_rebalance_tree(ir) || progress;
progress = do_algebraic(ir, native_integers, options) || progress;
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index b83c225..9d22585 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -98,6 +98,7 @@ bool opt_flatten_nested_if_blocks(exec_list *instructions);
bool do_discard_simplification(exec_list *instructions);
bool lower_if_to_cond_assign(exec_list *instructions, unsigned max_depth = 0);
bool do_mat_op_to_vec(exec_list *instructions);
+bool do_minmax_prune(exec_list *instructions);
bool do_noop_swizzle(exec_list *instructions);
bool do_structure_splitting(exec_list *instructions);
bool do_swizzle_swizzle(exec_list *instructions);
diff --git a/src/glsl/opt_minmax.cpp b/src/glsl/opt_minmax.cpp
new file mode 100644
index 0000000..5656059
--- /dev/null
+++ b/src/glsl/opt_minmax.cpp
@@ -0,0 +1,395 @@
+/*
+ * 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_minmax.cpp
+ *
+ * Drop operands from an expression tree of only min/max operations if they
+ * can be proven to not contribute to the final result.
+ *
+ * The algorithm is similar to alpha-beta pruning on a minmax search.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_rvalue_visitor.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+#include "main/macros.h"
+
+namespace
+{
+class minmax_range
+{
+public:
+
+ minmax_range(ir_constant *low = NULL, ir_constant *high = NULL)
+ {
+ range[0] = low;
+ range[1] = high;
+ }
+
+ /* [0] is the lower limit of the range, [1] is the higher limit. NULL on
+ * [0] means negative infinity (unlimited) and on [1] positive infinity
+ * (unlimited). Because of the two interpretations of the value NULL,
+ * arbitrary comparison between ir_constants is impossible.
+ */
+ ir_constant *range[2];
+};
+
+class ir_minmax_visitor : public ir_rvalue_enter_visitor {
+public:
+ ir_minmax_visitor()
+ : progress(false)
+ , valid(true)
+ {
+ }
+
+ virtual ~ir_minmax_visitor()
+ {
+ }
+
+ bool
+ less_all_components(ir_constant *one, ir_constant *two);
+
+ ir_constant *
+ smaller_constant(ir_constant *one, ir_constant *two);
+
+ ir_constant *
+ larger_constant(ir_constant *one, ir_constant *two);
+
+ minmax_range
+ combine_range(minmax_range r0, minmax_range r1, bool ismin);
+
+ minmax_range
+ range_intersection(minmax_range r0, minmax_range r1);
+
+ minmax_range
+ get_range(ir_rvalue *rval);
+
+ ir_rvalue *
+ prune_expression(ir_expression *expr, minmax_range baserange);
+
+ void
+ handle_rvalue(ir_rvalue **rvalue);
+
+ bool progress;
+ bool valid;
+};
+
+/*
+ * Returns true if all vector components of `one' are less than of `two'.
+ *
+ * If there are vector components that are less while others are greater, the
+ * visitor is marked invalid and no further changes will be made to the IR.
+ */
+bool
+ir_minmax_visitor::less_all_components(ir_constant *one, ir_constant *two)
+{
+ assert(one != NULL);
+ assert(two != NULL);
+
+ assert(one->type->base_type == two->type->base_type);
+
+ unsigned oneinc = one->type->is_scalar() ? 0 : 1;
+ unsigned twoinc = two->type->is_scalar() ? 0 : 1;
+ unsigned components = MAX2(one->type->components(), two->type->components());
+
+ /* No early escape. We need to go through all components and mark the
+ * visitor as invalid if comparison yields less for some components and
+ * greater for others. If some components compare as equal, it's not
+ * invalid.
+ */
+
+ bool foundless = false;
+ bool foundgreater = false;
+ bool foundequal = false;
+
+ for (unsigned i = 0, c0 = 0, c1 = 0;
+ i < components;
+ c0 += oneinc, c1 += twoinc, ++i) {
+ switch (one->type->base_type) {
+ case GLSL_TYPE_UINT:
+ if (one->value.u[c0] < two->value.u[c1])
+ foundless = true;
+ else if (one->value.u[c0] > two->value.u[c1])
+ foundgreater = true;
+ else
+ foundequal = true;
+ continue;
+ case GLSL_TYPE_INT:
+ if (one->value.i[c0] < two->value.i[c1])
+ foundless = true;
+ else if (one->value.i[c0] > two->value.i[c1])
+ foundgreater = true;
+ else
+ foundequal = true;
+ continue;
+ case GLSL_TYPE_FLOAT:
+ if (one->value.f[c0] < two->value.f[c1])
+ foundless = true;
+ else if (one->value.f[c0] > two->value.f[c1])
+ foundgreater = true;
+ else
+ foundequal = true;
+ continue;
+ default:
+ assert(!"not reached");
+ }
+ }
+
+ if (foundless && foundgreater) {
+ valid = false;
+ return false;
+ }
+
+ if (foundequal)
+ return false;
+
+ return foundless;
+}
+
+ir_constant *
+ir_minmax_visitor::smaller_constant(ir_constant *one, ir_constant *two)
+{
+ assert(one != NULL);
+ assert(two != NULL);
+
+ if (less_all_components(one, two))
+ return one;
+ else
+ return two;
+}
+
+ir_constant *
+ir_minmax_visitor::larger_constant(ir_constant *one, ir_constant *two)
+{
+ assert(one != NULL);
+ assert(two != NULL);
+
+ if (less_all_components(one, two))
+ return two;
+ else
+ return one;
+}
+
+/* Combines two ranges by doing an element-wise min() / max() depending on the
+ * operation.
+ */
+minmax_range
+ir_minmax_visitor::combine_range(minmax_range r0, minmax_range r1, bool ismin)
+{
+ minmax_range ret;
+
+ if (!r0.range[0]) {
+ ret.range[0] = ismin ? r0.range[0] : r1.range[0];
+ } else if (!r1.range[0]) {
+ ret.range[0] = ismin ? r1.range[0] : r0.range[0];
+ } else {
+ ret.range[0] = ismin ? smaller_constant(r0.range[0], r1.range[0]) :
+ larger_constant(r0.range[0], r1.range[0]);
+ }
+
+ if (!r0.range[1]) {
+ ret.range[1] = ismin ? r1.range[1] : r0.range[1];
+ } else if (!r1.range[1]) {
+ ret.range[1] = ismin ? r0.range[1] : r1.range[1];
+ } else {
+ ret.range[1] = ismin ? smaller_constant(r0.range[1], r1.range[1]) :
+ larger_constant(r0.range[1], r1.range[1]);
+ }
+
+ return ret;
+}
+
+/* Returns a range so that lower limit is the larger of the two lower limits,
+ * and higher limit is the smaller of the two higher limits.
+ */
+minmax_range
+ir_minmax_visitor::range_intersection(minmax_range r0, minmax_range r1)
+{
+ minmax_range ret;
+
+ if (!r0.range[0])
+ ret.range[0] = r1.range[0];
+ else if (!r1.range[0])
+ ret.range[0] = r0.range[0];
+ else
+ ret.range[0] = larger_constant(r0.range[0], r1.range[0]);
+
+ if (!r0.range[1])
+ ret.range[1] = r1.range[1];
+ else if (!r1.range[1])
+ ret.range[1] = r0.range[1];
+ else
+ ret.range[1] = smaller_constant(r0.range[1], r1.range[1]);
+
+ return ret;
+}
+
+minmax_range
+ir_minmax_visitor::get_range(ir_rvalue *rval)
+{
+ if (ir_expression *expr = rval->as_expression()) {
+ if (expr->operation == ir_binop_min ||
+ expr->operation == ir_binop_max) {
+ minmax_range r0 = get_range(expr->operands[0]);
+ minmax_range r1 = get_range(expr->operands[1]);
+
+ return combine_range(r0, r1, expr->operation == ir_binop_min);
+ }
+ }
+
+ if (ir_constant *c = rval->as_constant()) {
+ return minmax_range(c, c);
+ }
+
+ return minmax_range();
+}
+
+ir_rvalue *
+ir_minmax_visitor::prune_expression(ir_expression *expr, minmax_range baserange)
+{
+ assert(expr->operation == ir_binop_min ||
+ expr->operation == ir_binop_max);
+
+ if (!valid)
+ return expr;
+
+ bool ismin = expr->operation == ir_binop_min;
+ minmax_range limits[2];
+
+ for (unsigned i = 0; i < 2; ++i) {
+ limits[i] = get_range(expr->operands[i]);
+ }
+
+ for (unsigned i = 0; i < 2; ++i) {
+ /* Operands are dropped if their range doesn't reach the given baserange
+ * or the other operand's limit from the appropriate direction.
+ */
+
+ minmax_range basereach;
+ minmax_range otherreach;
+
+ if (ismin) {
+ basereach.range[0] = limits[i].range[0];
+ otherreach.range[0] = limits[i].range[0];
+ basereach.range[1] = baserange.range[1];
+ otherreach.range[1] = limits[1 - i].range[1];
+ } else {
+ basereach.range[0] = baserange.range[0];
+ otherreach.range[0] = limits[1 - i].range[0];
+ basereach.range[1] = limits[i].range[1];
+ otherreach.range[1] = limits[i].range[1];
+ }
+
+ if ((basereach.range[0] && basereach.range[1] &&
+ !less_all_components(basereach.range[0], basereach.range[1])) ||
+ (otherreach.range[0] && otherreach.range[1] &&
+ !less_all_components(otherreach.range[0], otherreach.range[1]))) {
+ /* Bail out if those comparisons made the visitor invalid. */
+ if (!valid)
+ return expr;
+
+ progress = true;
+
+ /* Recurse if necessary. */
+ if (ir_expression* opexpr = expr->operands[1 - i]->as_expression()) {
+ if (opexpr->operation == ir_binop_min ||
+ opexpr->operation == ir_binop_max) {
+ return prune_expression(opexpr, baserange);
+ }
+ }
+
+ return expr->operands[1 - i];
+ }
+ }
+
+ /* Now recurse to operands giving them the proper baserange. The baserange
+ * to pass is the intersection of our baserange and the other operand's
+ * limit with one of the ranges unlimited.
+ */
+
+ unsigned clear = (ismin ? 0 : 1);
+
+ for (unsigned i = 0; i < 2; ++i) {
+ if (ir_expression *opexpr = expr->operands[i]->as_expression()) {
+ if (opexpr->operation == ir_binop_min ||
+ opexpr->operation == ir_binop_max) {
+ limits[1 - i].range[clear] = NULL;
+ minmax_range base = range_intersection(limits[1 - i], baserange);
+ expr->operands[i] = prune_expression(opexpr, base);
+ }
+ }
+ }
+
+ return expr;
+}
+
+ir_rvalue *
+swizzle_if_required(ir_expression *expr,
+ ir_rvalue *rval)
+{
+ if (expr->type->is_vector() && rval->type->is_scalar()) {
+ return new(expr) ir_swizzle(rval, 0, 0, 0, 0,
+ expr->type->vector_elements);
+ } else {
+ return rval;
+ }
+}
+
+void
+ir_minmax_visitor::handle_rvalue(ir_rvalue **rvalue)
+{
+ if (!*rvalue)
+ return;
+
+ ir_expression *expr = (*rvalue)->as_expression();
+ if (!expr || (expr->operation != ir_binop_min &&
+ expr->operation != ir_binop_max))
+ return;
+
+ ir_rvalue *new_rvalue = prune_expression(expr, minmax_range());
+ if (!valid || new_rvalue == *rvalue) {
+ return;
+ }
+
+ /* If the expression type is a vector and the optimization leaves a scalar
+ * as the result, we need to turn it into a vector.
+ */
+ *rvalue = swizzle_if_required(expr, new_rvalue);
+
+ progress = true;
+}
+
+}
+
+bool
+do_minmax_prune(exec_list *instructions)
+{
+ ir_minmax_visitor v;
+
+ visit_list_elements(&v, instructions);
+
+ return v.progress;
+}
--
2.0.1
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