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glsl/linker: eliminate unused and set-but-unused built-in varyings

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This eliminates built-in varyings such as gl_Color, gl_SecondaryColor,
gl_TexCoord, and gl_FogFragCoord if they are unused by the next stage or
not written at all (e.g. gl_TexCoord elements). The gl_TexCoord array is
broken down into separate vec4s if needed.

v2: - use a switch statement in varying_info_visitor::visit(ir_variable*)
    - use snprintf
    - disable the optimization for GLES2

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Marek Olšák
2013-06-12 13:23:48 +02:00
parent 3c555827c3
commit b3d8b4c0b4
5 changed files with 496 additions and 2 deletions
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476
src/glsl/opt_dead_builtin_varyings.cpp Normal file
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/*
* Copyright © 2013 Marek Olšák <maraeo@gmail.com>
*
* 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_dead_builtin_varyings.cpp
*
* This eliminates the built-in shader outputs which are either not written
* at all or not used by the next stage. It also eliminates unused elements
* of gl_TexCoord inputs, which reduces the overall varying usage.
* The varyings handled here are the primary and secondary color, the fog,
* and the texture coordinates (gl_TexCoord).
*
* This pass is necessary, because the Mesa GLSL linker cannot eliminate
* built-in varyings like it eliminates user-defined varyings, because
* the built-in varyings have pre-assigned locations. Also, the elimination
* of unused gl_TexCoord elements requires its own lowering pass anyway.
*
* It's implemented by replacing all occurences of dead varyings with
* temporary variables, which creates dead code. It is recommended to run
* a dead-code elimination pass after this.
*
* If any texture coordinate slots can be eliminated, the gl_TexCoord array is
* broken down into separate vec4 variables with locations equal to
* VARYING_SLOT_TEX0 + i.
*/
#include "ir.h"
#include "ir_rvalue_visitor.h"
#include "ir_optimization.h"
#include "ir_print_visitor.h"
#include "glsl_types.h"
#include "link_varyings.h"
/**
* This obtains detailed information about built-in varyings from shader code.
*/
class varying_info_visitor : public ir_hierarchical_visitor {
public:
/* "mode" can be either ir_var_shader_in or ir_var_shader_out */
varying_info_visitor(ir_variable_mode mode)
: lower_texcoord_array(true),
texcoord_array(NULL),
texcoord_usage(0),
color_usage(0),
tfeedback_color_usage(0),
fog(NULL),
has_fog(false),
tfeedback_has_fog(false),
mode(mode)
{
memset(color, 0, sizeof(color));
memset(backcolor, 0, sizeof(backcolor));
}
virtual ir_visitor_status visit_enter(ir_dereference_array *ir)
{
ir_variable *var = ir->variable_referenced();
if (var && var->mode == this->mode &&
var->location == VARYING_SLOT_TEX0) {
this->texcoord_array = var;
ir_constant *index = ir->array_index->as_constant();
if (index == NULL) {
/* There is variable indexing, we can't lower the texcoord array.
*/
this->texcoord_usage |= (1 << var->type->array_size()) - 1;
this->lower_texcoord_array = false;
}
else {
this->texcoord_usage |= 1 << index->get_uint_component(0);
}
/* Don't visit the leaves of ir_dereference_array. */
return visit_continue_with_parent;
}
return visit_continue;
}
virtual ir_visitor_status visit(ir_dereference_variable *ir)
{
ir_variable *var = ir->variable_referenced();
if (var->mode == this->mode && var->type->is_array() &&
var->location == VARYING_SLOT_TEX0) {
/* This is a whole array dereference like "gl_TexCoord = x;",
* there's probably no point in lowering that.
*/
this->texcoord_usage |= (1 << var->type->array_size()) - 1;
this->lower_texcoord_array = false;
}
return visit_continue;
}
virtual ir_visitor_status visit(ir_variable *var)
{
if (var->mode != this->mode)
return visit_continue;
/* Handle colors and fog. */
switch (var->location) {
case VARYING_SLOT_COL0:
this->color[0] = var;
this->color_usage |= 1;
break;
case VARYING_SLOT_COL1:
this->color[1] = var;
this->color_usage |= 2;
break;
case VARYING_SLOT_BFC0:
this->backcolor[0] = var;
this->color_usage |= 1;
break;
case VARYING_SLOT_BFC1:
this->backcolor[1] = var;
this->color_usage |= 2;
break;
case VARYING_SLOT_FOGC:
this->fog = var;
this->has_fog = true;
break;
}
return visit_continue;
}
void get(exec_list *ir,
unsigned num_tfeedback_decls,
tfeedback_decl *tfeedback_decls)
{
/* Handle the transform feedback varyings. */
for (unsigned i = 0; i < num_tfeedback_decls; i++) {
if (!tfeedback_decls[i].is_varying())
continue;
unsigned location = tfeedback_decls[i].get_location();
switch (location) {
case VARYING_SLOT_COL0:
case VARYING_SLOT_BFC0:
this->tfeedback_color_usage |= 1;
break;
case VARYING_SLOT_COL1:
case VARYING_SLOT_BFC1:
this->tfeedback_color_usage |= 2;
break;
case VARYING_SLOT_FOGC:
this->tfeedback_has_fog = true;
break;
default:
if (location >= VARYING_SLOT_TEX0 &&
location <= VARYING_SLOT_TEX7) {
this->lower_texcoord_array = false;
}
}
}
/* Process the shader. */
visit_list_elements(this, ir);
if (!this->texcoord_array) {
this->lower_texcoord_array = false;
}
}
bool lower_texcoord_array;
ir_variable *texcoord_array;
unsigned texcoord_usage; /* bitmask */
ir_variable *color[2];
ir_variable *backcolor[2];
unsigned color_usage; /* bitmask */
unsigned tfeedback_color_usage; /* bitmask */
ir_variable *fog;
bool has_fog;
bool tfeedback_has_fog;
ir_variable_mode mode;
};
/**
* This replaces unused varyings with temporary variables.
*
* If "ir" is the producer, the "external" usage should come from
* the consumer. It also works the other way around. If either one is
* missing, set the "external" usage to a full mask.
*/
class replace_varyings_visitor : public ir_rvalue_visitor {
public:
replace_varyings_visitor(exec_list *ir,
const varying_info_visitor *info,
unsigned external_texcoord_usage,
unsigned external_color_usage,
bool external_has_fog)
: info(info), new_fog(NULL)
{
void *const ctx = ir;
memset(this->new_texcoord, 0, sizeof(this->new_texcoord));
memset(this->new_color, 0, sizeof(this->new_color));
memset(this->new_backcolor, 0, sizeof(this->new_backcolor));
const char *mode_str =
info->mode == ir_var_shader_in ? "in" : "out";
/* Handle texcoord outputs.
*
* We're going to break down the gl_TexCoord array into separate
* variables. First, add declarations of the new variables all
* occurences of gl_TexCoord will be replaced with.
*/
if (info->lower_texcoord_array) {
for (int i = MAX_TEXTURE_COORD_UNITS-1; i >= 0; i--) {
if (info->texcoord_usage & (1 << i)) {
char name[32];
if (!(external_texcoord_usage & (1 << i))) {
/* This varying is unused in the next stage. Declare
* a temporary instead of an output. */
snprintf(name, 32, "gl_%s_TexCoord%i_dummy", mode_str, i);
this->new_texcoord[i] =
new (ctx) ir_variable(glsl_type::vec4_type, name,
ir_var_temporary);
}
else {
snprintf(name, 32, "gl_%s_TexCoord%i", mode_str, i);
this->new_texcoord[i] =
new(ctx) ir_variable(glsl_type::vec4_type, name,
info->mode);
this->new_texcoord[i]->location = VARYING_SLOT_TEX0 + i;
this->new_texcoord[i]->explicit_location = true;
this->new_texcoord[i]->explicit_index = 0;
}
ir->head->insert_before(new_texcoord[i]);
}
}
}
/* Create dummy variables which will replace set-but-unused color and
* fog outputs.
*/
external_color_usage |= info->tfeedback_color_usage;
for (int i = 0; i < 2; i++) {
char name[32];
if (!(external_color_usage & (1 << i))) {
if (info->color[i]) {
snprintf(name, 32, "gl_%s_FrontColor%i_dummy", mode_str, i);
this->new_color[i] =
new (ctx) ir_variable(glsl_type::vec4_type, name,
ir_var_temporary);
}
if (info->backcolor[i]) {
snprintf(name, 32, "gl_%s_BackColor%i_dummy", mode_str, i);
this->new_backcolor[i] =
new (ctx) ir_variable(glsl_type::vec4_type, name,
ir_var_temporary);
}
}
}
if (!external_has_fog && !info->tfeedback_has_fog &&
info->fog) {
char name[32];
snprintf(name, 32, "gl_%s_FogFragCoord_dummy", mode_str);
this->new_fog = new (ctx) ir_variable(glsl_type::float_type, name,
ir_var_temporary);
}
/* Now do the replacing. */
visit_list_elements(this, ir);
}
virtual ir_visitor_status visit(ir_variable *var)
{
/* Remove the gl_TexCoord array. */
if (this->info->lower_texcoord_array &&
var == this->info->texcoord_array) {
var->remove();
}
/* Replace set-but-unused color and fog outputs with dummy variables. */
for (int i = 0; i < 2; i++) {
if (var == this->info->color[i] && this->new_color[i]) {
var->replace_with(this->new_color[i]);
}
if (var == this->info->backcolor[i] &&
this->new_backcolor[i]) {
var->replace_with(this->new_backcolor[i]);
}
}
if (var == this->info->fog && this->new_fog) {
var->replace_with(this->new_fog);
}
return visit_continue;
}
virtual void handle_rvalue(ir_rvalue **rvalue)
{
if (!*rvalue)
return;
void *ctx = ralloc_parent(*rvalue);
/* Replace an array dereference gl_TexCoord[i] with a single
* variable dereference representing gl_TexCoord[i].
*/
if (this->info->lower_texcoord_array) {
/* gl_TexCoord[i] occurence */
ir_dereference_array *const da = (*rvalue)->as_dereference_array();
if (da && da->variable_referenced() ==
this->info->texcoord_array) {
unsigned i = da->array_index->as_constant()->get_uint_component(0);
*rvalue = new(ctx) ir_dereference_variable(this->new_texcoord[i]);
return;
}
}
/* Replace set-but-unused color and fog outputs with dummy variables. */
ir_dereference_variable *const dv = (*rvalue)->as_dereference_variable();
if (!dv)
return;
ir_variable *var = dv->variable_referenced();
for (int i = 0; i < 2; i++) {
if (var == this->info->color[i] && this->new_color[i]) {
*rvalue = new(ctx) ir_dereference_variable(this->new_color[i]);
return;
}
if (var == this->info->backcolor[i] &&
this->new_backcolor[i]) {
*rvalue = new(ctx) ir_dereference_variable(this->new_backcolor[i]);
return;
}
}
if (var == this->info->fog && this->new_fog) {
*rvalue = new(ctx) ir_dereference_variable(this->new_fog);
}
}
virtual ir_visitor_status visit_leave(ir_assignment *ir)
{
handle_rvalue(&ir->rhs);
handle_rvalue(&ir->condition);
/* We have to use set_lhs when changing the LHS of an assignment. */
ir_rvalue *lhs = ir->lhs;
handle_rvalue(&lhs);
if (lhs != ir->lhs) {
ir->set_lhs(lhs);
}
return visit_continue;
}
private:
const varying_info_visitor *info;
struct ir_variable *new_texcoord[MAX_TEXTURE_COORD_UNITS];
struct ir_variable *new_color[2];
struct ir_variable *new_backcolor[2];
struct ir_variable *new_fog;
};
static void
lower_texcoord_array(exec_list *ir, const varying_info_visitor *info)
{
replace_varyings_visitor(ir, info,
(1 << MAX_TEXTURE_COORD_UNITS) - 1,
1 | 2, true);
}
void
do_dead_builtin_varyings(struct gl_context *ctx,
exec_list *producer, exec_list *consumer,
unsigned num_tfeedback_decls,
tfeedback_decl *tfeedback_decls)
{
/* This optimization has no effect with the core context and GLES2, because
* the built-in varyings we're eliminating here are not available there.
*
* EXT_separate_shader_objects doesn't allow this optimization,
* because a program object can be bound partially (e.g. only one
* stage of a program object can be bound).
*/
if (ctx->API == API_OPENGL_CORE ||
ctx->API == API_OPENGLES2 ||
ctx->Extensions.EXT_separate_shader_objects) {
return;
}
/* Information about built-in varyings. */
varying_info_visitor producer_info(ir_var_shader_out);
varying_info_visitor consumer_info(ir_var_shader_in);
if (producer) {
producer_info.get(producer, num_tfeedback_decls, tfeedback_decls);
if (!consumer) {
/* At least eliminate unused gl_TexCoord elements. */
if (producer_info.lower_texcoord_array) {
lower_texcoord_array(producer, &producer_info);
}
return;
}
}
if (consumer) {
consumer_info.get(consumer, 0, NULL);
if (!producer) {
/* At least eliminate unused gl_TexCoord elements. */
if (consumer_info.lower_texcoord_array) {
lower_texcoord_array(consumer, &consumer_info);
}
return;
}
}
/* Eliminate the varyings unused by the other shader. */
if (producer_info.lower_texcoord_array ||
producer_info.color_usage ||
producer_info.has_fog) {
replace_varyings_visitor(producer,
&producer_info,
consumer_info.texcoord_usage,
consumer_info.color_usage,
consumer_info.has_fog);
}
if (consumer_info.lower_texcoord_array ||
consumer_info.color_usage ||
consumer_info.has_fog) {
replace_varyings_visitor(consumer,
&consumer_info,
producer_info.texcoord_usage,
producer_info.color_usage,
producer_info.has_fog);
}
}