/*
* 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 "ir_builder.h"
#include "program/prog_instruction.h"
#include "glsl_types.h"
#include "main/macros.h"
using namespace ir_builder;
namespace {
enum compare_components_result {
LESS,
LESS_OR_EQUAL,
EQUAL,
GREATER_OR_EQUAL,
GREATER,
MIXED
};
class minmax_range {
public:
minmax_range(ir_constant *low = NULL, ir_constant *high = NULL)
{
this->low = low;
this->high = high;
}
/* low is the lower limit of the range, high is the higher limit. NULL on
* low means negative infinity (unlimited) and on high positive infinity
* (unlimited). Because of the two interpretations of the value NULL,
* arbitrary comparison between ir_constants is impossible.
*/
ir_constant *low;
ir_constant *high;
};
class ir_minmax_visitor : public ir_rvalue_enter_visitor {
public:
ir_minmax_visitor()
: progress(false)
{
}
ir_rvalue *prune_expression(ir_expression *expr, minmax_range baserange);
void handle_rvalue(ir_rvalue **rvalue);
bool progress;
};
/*
* Returns LESS if all vector components of `a' are strictly lower than of `b',
* GREATER if all vector components of `a' are strictly greater than of `b',
* MIXED if some vector components of `a' are strictly lower than of `b' while
* others are strictly greater, or EQUAL otherwise.
*/
static enum compare_components_result
compare_components(ir_constant *a, ir_constant *b)
{
assert(a != NULL);
assert(b != NULL);
assert(a->type->base_type == b->type->base_type);
unsigned a_inc = a->type->is_scalar() ? 0 : 1;
unsigned b_inc = b->type->is_scalar() ? 0 : 1;
unsigned components = MAX2(a->type->components(), b->type->components());
bool foundless = false;
bool foundgreater = false;
bool foundequal = false;
for (unsigned i = 0, c0 = 0, c1 = 0;
i < components;
c0 += a_inc, c1 += b_inc, ++i) {
switch (a->type->base_type) {
case GLSL_TYPE_UINT:
if (a->value.u[c0] < b->value.u[c1])
foundless = true;
else if (a->value.u[c0] > b->value.u[c1])
foundgreater = true;
else
foundequal = true;
break;
case GLSL_TYPE_INT:
if (a->value.i[c0] < b->value.i[c1])
foundless = true;
else if (a->value.i[c0] > b->value.i[c1])
foundgreater = true;
else
foundequal = true;
break;
case GLSL_TYPE_FLOAT:
if (a->value.f[c0] < b->value.f[c1])
foundless = true;
else if (a->value.f[c0] > b->value.f[c1])
foundgreater = true;
else
foundequal = true;
break;
case GLSL_TYPE_DOUBLE:
if (a->value.d[c0] < b->value.d[c1])
foundless = true;
else if (a->value.d[c0] > b->value.d[c1])
foundgreater = true;
else
foundequal = true;
break;
default:
unreachable("not reached");
}
}
if (foundless && foundgreater) {
/* Some components are strictly lower, others are strictly greater */
return MIXED;
}
if (foundequal) {
/* It is not mixed, but it is not strictly lower or greater */
if (foundless)
return LESS_OR_EQUAL;
if (foundgreater)
return GREATER_OR_EQUAL;
return EQUAL;
}
/* All components are strictly lower or strictly greater */
return foundless ? LESS : GREATER;
}
static ir_constant *
combine_constant(bool ismin, ir_constant *a, ir_constant *b)
{
void *mem_ctx = ralloc_parent(a);
ir_constant *c = a->clone(mem_ctx, NULL);
for (unsigned i = 0; i < c->type->components(); i++) {
switch (c->type->base_type) {
case GLSL_TYPE_UINT:
if ((ismin && b->value.u[i] < c->value.u[i]) ||
(!ismin && b->value.u[i] > c->value.u[i]))
c->value.u[i] = b->value.u[i];
break;
case GLSL_TYPE_INT:
if ((ismin && b->value.i[i] < c->value.i[i]) ||
(!ismin && b->value.i[i] > c->value.i[i]))
c->value.i[i] = b->value.i[i];
break;
case GLSL_TYPE_FLOAT:
if ((ismin && b->value.f[i] < c->value.f[i]) ||
(!ismin && b->value.f[i] > c->value.f[i]))
c->value.f[i] = b->value.f[i];
break;
case GLSL_TYPE_DOUBLE:
if ((ismin && b->value.d[i] < c->value.d[i]) ||
(!ismin && b->value.d[i] > c->value.d[i]))
c->value.d[i] = b->value.d[i];
break;
default:
assert(!"not reached");
}
}
return c;
}
static ir_constant *
smaller_constant(ir_constant *a, ir_constant *b)
{
assert(a != NULL);
assert(b != NULL);
enum compare_components_result ret = compare_components(a, b);
if (ret == MIXED)
return combine_constant(true, a, b);
else if (ret < EQUAL)
return a;
else
return b;
}
static ir_constant *
larger_constant(ir_constant *a, ir_constant *b)
{
assert(a != NULL);
assert(b != NULL);
enum compare_components_result ret = compare_components(a, b);
if (ret == MIXED)
return combine_constant(false, a, b);
else if (ret < EQUAL)
return b;
else
return a;
}
/* Combines two ranges by doing an element-wise min() / max() depending on the
* operation.
*/
static minmax_range
combine_range(minmax_range r0, minmax_range r1, bool ismin)
{
minmax_range ret;
if (!r0.low) {
ret.low = ismin ? r0.low : r1.low;
} else if (!r1.low) {
ret.low = ismin ? r1.low : r0.low;
} else {
ret.low = ismin ? smaller_constant(r0.low, r1.low) :
larger_constant(r0.low, r1.low);
}
if (!r0.high) {
ret.high = ismin ? r1.high : r0.high;
} else if (!r1.high) {
ret.high = ismin ? r0.high : r1.high;
} else {
ret.high = ismin ? smaller_constant(r0.high, r1.high) :
larger_constant(r0.high, r1.high);
}
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.
*/
static minmax_range
range_intersection(minmax_range r0, minmax_range r1)
{
minmax_range ret;
if (!r0.low)
ret.low = r1.low;
else if (!r1.low)
ret.low = r0.low;
else
ret.low = larger_constant(r0.low, r1.low);
if (!r0.high)
ret.high = r1.high;
else if (!r1.high)
ret.high = r0.high;
else
ret.high = smaller_constant(r0.high, r1.high);
return ret;
}
static minmax_range
get_range(ir_rvalue *rval)
{
ir_expression *expr = rval->as_expression();
if (expr && (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);
}
ir_constant *c = rval->as_constant();
if (c) {
return minmax_range(c, c);
}
return minmax_range();
}
/**
* Prunes a min/max expression considering the base range of the parent
* min/max expression.
*
* @param baserange the range that the parents of this min/max expression
* in the min/max tree will clamp its value to.
*/
ir_rvalue *
ir_minmax_visitor::prune_expression(ir_expression *expr, minmax_range baserange)
{
assert(expr->operation == ir_binop_min ||
expr->operation == ir_binop_max);
bool ismin = expr->operation == ir_binop_min;
minmax_range limits[2];
/* Recurse to get the ranges for each of the subtrees of this
* expression. We need to do this as a separate step because we need to
* know the ranges of each of the subtrees before we prune either one.
* Consider something like this:
*
* max
* / \
* max max
* / \ / \
* 3 a b 2
*
* We would like to prune away the max on the bottom-right, but to do so
* we need to know the range of the expression on the left beforehand,
* and there's no guarantee that we will visit either subtree in a
* particular order.
*/
for (unsigned i = 0; i < 2; ++i)
limits[i] = get_range(expr->operands[i]);
for (unsigned i = 0; i < 2; ++i) {
bool is_redundant = false;
enum compare_components_result cr = LESS;
if (ismin) {
/* If this operand will always be greater than the other one, it's
* redundant.
*/
if (limits[i].low && limits[1 - i].high) {
cr = compare_components(limits[i].low, limits[1 - i].high);
if (cr >= EQUAL && cr != MIXED)
is_redundant = true;
}
/* If this operand is always greater than baserange, then even if
* it's smaller than the other one it'll get clamped, so it's
* redundant.
*/
if (!is_redundant && limits[i].low && baserange.high) {
cr = compare_components(limits[i].low, baserange.high);
if (cr >= EQUAL && cr != MIXED)
is_redundant = true;
}
} else {
/* If this operand will always be lower than the other one, it's
* redundant.
*/
if (limits[i].high && limits[1 - i].low) {
cr = compare_components(limits[i].high, limits[1 - i].low);
if (cr <= EQUAL)
is_redundant = true;
}
/* If this operand is always lower than baserange, then even if
* it's greater than the other one it'll get clamped, so it's
* redundant.
*/
if (!is_redundant && limits[i].high && baserange.low) {
cr = compare_components(limits[i].high, baserange.low);
if (cr <= EQUAL)
is_redundant = true;
}
}
if (is_redundant) {
progress = true;
/* Recurse if necessary. */
ir_expression *op_expr = expr->operands[1 - i]->as_expression();
if (op_expr && (op_expr->operation == ir_binop_min ||
op_expr->operation == ir_binop_max)) {
return prune_expression(op_expr, baserange);
}
return expr->operands[1 - i];
} else if (cr == MIXED) {
/* If we have mixed vector operands, we can try to resolve the minmax
* expression by doing a component-wise minmax:
*
* min min
* / \ / \
* min a ===> [1,1] a
* / \
* [1,3] [3,1]
*
*/
ir_constant *a = expr->operands[0]->as_constant();
ir_constant *b = expr->operands[1]->as_constant();
if (a && b)
return combine_constant(ismin, a, b);
}
}
/* 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. If we can't compute a valid
* intersection, we use the current baserange.
*/
for (unsigned i = 0; i < 2; ++i) {
ir_expression *op_expr = expr->operands[i]->as_expression();
if (op_expr && (op_expr->operation == ir_binop_min ||
op_expr->operation == ir_binop_max)) {
/* We can only compute a new baserange for this operand if we managed
* to compute a valid range for the other operand.
*/
if (ismin)
limits[1 - i].low = NULL;
else
limits[1 - i].high = NULL;
minmax_range base = range_intersection(limits[1 - i], baserange);
expr->operands[i] = prune_expression(op_expr, base);
}
}
/* If we got here we could not discard any of the operands of the minmax
* expression, but we can still try to resolve the expression if both
* operands are constant. We do this after the loop above, to make sure
* that if our operands are minmax expressions we have tried to prune them
* first (hopefully reducing them to constants).
*/
ir_constant *a = expr->operands[0]->as_constant();
ir_constant *b = expr->operands[1]->as_constant();
if (a && b)
return combine_constant(ismin, a, b);
return expr;
}
static ir_rvalue *
swizzle_if_required(ir_expression *expr, ir_rvalue *rval)
{
if (expr->type->is_vector() && rval->type->is_scalar()) {
return swizzle(rval, SWIZZLE_XXXX, 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 (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;
}