[Mesa-dev] [PATCH 1/9] glsl: Optimize min/max expression trees
Ian Romanick
idr at freedesktop.org
Wed Aug 13 18:33:32 PDT 2014
On 07/29/2014 02:36 AM, Petri Latvala wrote:
> 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.
And I assume no piglit regressions?
Also... have you tried this in combination with Abdiel's related work on
saturates?
> 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;
Since there's nothing else in the loop, I'd rather see these be break
statements. Seeing continue here is a weird and a little unnerving.
> + 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");
Use unreachable("Invalid type") here.
> + }
> + }
> +
> + 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;
> +}
>
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