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glsl: break the gl_FragData array into separate gl_FragData[i] variables

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This avoids a defect in lower_output_reads.

The problem is lower_output_reads treats the gl_FragData array as a single
variable. It first redirects all output writes to a temporary variable (array)
and then writes the whole temporary variable to the output, generating
assignments to all elements of gl_FragData.

BTW this pass can be modified to lower all arrays, not just inputs and outputs.
The question is whether it is worth it.

Reviewed-by: Paul Berry <stereotype441@gmail.com>

v2: addressed Paul Berry's comments
This commit is contained in:
Marek Olšák 2013-10-20 05:15:42 +02:00
parent aec20d66d9
commit 7e414b5864
1 changed files with 133 additions and 32 deletions
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165
src/glsl/opt_dead_builtin_varyings.cpp
View file

@ -42,9 +42,11 @@
* 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.
*
* The same is done for the gl_FragData fragment shader output.
*/
#include "main/imports.h" /* for snprintf */
#include "main/core.h" /* for snprintf and ARRAY_SIZE */
#include "ir.h"
#include "ir_rvalue_visitor.h"
#include "ir_optimization.h"
@ -60,10 +62,14 @@ namespace {
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)
varying_info_visitor(ir_variable_mode mode, bool find_frag_outputs = false)
: lower_texcoord_array(true),
texcoord_array(NULL),
texcoord_usage(0),
find_frag_outputs(find_frag_outputs),
lower_fragdata_array(true),
fragdata_array(NULL),
fragdata_usage(0),
color_usage(0),
tfeedback_color_usage(0),
fog(NULL),
@ -79,8 +85,27 @@ public:
{
ir_variable *var = ir->variable_referenced();
if (var && var->mode == this->mode &&
var->location == VARYING_SLOT_TEX0) {
if (!var || var->mode != this->mode)
return visit_continue;
if (this->find_frag_outputs && var->location == FRAG_RESULT_DATA0) {
this->fragdata_array = var;
ir_constant *index = ir->array_index->as_constant();
if (index == NULL) {
/* This is variable indexing. */
this->fragdata_usage |= (1 << var->type->array_size()) - 1;
this->lower_fragdata_array = false;
}
else {
this->fragdata_usage |= 1 << index->get_uint_component(0);
}
/* Don't visit the leaves of ir_dereference_array. */
return visit_continue_with_parent;
}
if (!this->find_frag_outputs && var->location == VARYING_SLOT_TEX0) {
this->texcoord_array = var;
ir_constant *index = ir->array_index->as_constant();
@ -105,8 +130,17 @@ public:
{
ir_variable *var = ir->variable_referenced();
if (var->mode == this->mode && var->type->is_array() &&
var->location == VARYING_SLOT_TEX0) {
if (var->mode != this->mode || !var->type->is_array())
return visit_continue;
if (this->find_frag_outputs && var->location == FRAG_RESULT_DATA0) {
/* This is a whole array dereference. */
this->fragdata_usage |= (1 << var->type->array_size()) - 1;
this->lower_fragdata_array = false;
return visit_continue;
}
if (!this->find_frag_outputs && var->location == VARYING_SLOT_TEX0) {
/* This is a whole array dereference like "gl_TexCoord = x;",
* there's probably no point in lowering that.
*/
@ -121,6 +155,10 @@ public:
if (var->mode != this->mode)
return visit_continue;
/* Nothing to do here for fragment outputs. */
if (this->find_frag_outputs)
return visit_continue;
/* Handle colors and fog. */
switch (var->location) {
case VARYING_SLOT_COL0:
@ -185,12 +223,20 @@ public:
if (!this->texcoord_array) {
this->lower_texcoord_array = false;
}
if (!this->fragdata_array) {
this->lower_fragdata_array = false;
}
}
bool lower_texcoord_array;
ir_variable *texcoord_array;
unsigned texcoord_usage; /* bitmask */
bool find_frag_outputs; /* false if it's looking for varyings */
bool lower_fragdata_array;
ir_variable *fragdata_array;
unsigned fragdata_usage; /* bitmask */
ir_variable *color[2];
ir_variable *backcolor[2];
unsigned color_usage; /* bitmask */
@ -222,6 +268,7 @@ public:
{
void *const ctx = ir;
memset(this->new_fragdata, 0, sizeof(this->new_fragdata));
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));
@ -236,31 +283,16 @@ public:
* 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];
prepare_array(ir, this->new_texcoord, ARRAY_SIZE(this->new_texcoord),
VARYING_SLOT_TEX0, "TexCoord", mode_str,
info->texcoord_usage, external_texcoord_usage);
}
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]);
}
}
/* Handle gl_FragData in the same way like gl_TexCoord. */
if (info->lower_fragdata_array) {
prepare_array(ir, this->new_fragdata, ARRAY_SIZE(this->new_fragdata),
FRAG_RESULT_DATA0, "FragData", mode_str,
info->fragdata_usage, (1 << MAX_DRAW_BUFFERS) - 1);
}
/* Create dummy variables which will replace set-but-unused color and
@ -301,6 +333,41 @@ public:
visit_list_elements(this, ir);
}
void prepare_array(exec_list *ir,
struct ir_variable **new_var,
int max_elements, unsigned start_location,
const char *var_name, const char *mode_str,
unsigned usage, unsigned external_usage)
{
void *const ctx = ir;
for (int i = max_elements-1; i >= 0; i--) {
if (usage & (1 << i)) {
char name[32];
if (!(external_usage & (1 << i))) {
/* This varying is unused in the next stage. Declare
* a temporary instead of an output. */
snprintf(name, 32, "gl_%s_%s%i_dummy", mode_str, var_name, i);
new_var[i] =
new (ctx) ir_variable(glsl_type::vec4_type, name,
ir_var_temporary);
}
else {
snprintf(name, 32, "gl_%s_%s%i", mode_str, var_name, i);
new_var[i] =
new(ctx) ir_variable(glsl_type::vec4_type, name,
this->info->mode);
new_var[i]->location = start_location + i;
new_var[i]->explicit_location = true;
new_var[i]->explicit_index = 0;
}
ir->head->insert_before(new_var[i]);
}
}
}
virtual ir_visitor_status visit(ir_variable *var)
{
/* Remove the gl_TexCoord array. */
@ -309,6 +376,12 @@ public:
var->remove();
}
/* Remove the gl_FragData array. */
if (this->info->lower_fragdata_array &&
var == this->info->fragdata_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]) {
@ -350,6 +423,19 @@ public:
}
}
/* Same for gl_FragData. */
if (this->info->lower_fragdata_array) {
/* gl_FragData[i] occurence */
ir_dereference_array *const da = (*rvalue)->as_dereference_array();
if (da && da->variable_referenced() == this->info->fragdata_array) {
unsigned i = da->array_index->as_constant()->get_uint_component(0);
*rvalue = new(ctx) ir_dereference_variable(this->new_fragdata[i]);
return;
}
}
/* Replace set-but-unused color and fog outputs with dummy variables. */
ir_dereference_variable *const dv = (*rvalue)->as_dereference_variable();
if (!dv)
@ -392,6 +478,7 @@ public:
private:
const varying_info_visitor *info;
ir_variable *new_fragdata[MAX_DRAW_BUFFERS];
ir_variable *new_texcoord[MAX_TEXTURE_COORD_UNITS];
ir_variable *new_color[2];
ir_variable *new_backcolor[2];
@ -408,6 +495,15 @@ lower_texcoord_array(exec_list *ir, const varying_info_visitor *info)
1 | 2, true);
}
static void
lower_fragdata_array(exec_list *ir)
{
varying_info_visitor info(ir_var_shader_out, true);
info.get(ir, 0, NULL);
replace_varyings_visitor(ir, &info, 0, 0, 0);
}
void
do_dead_builtin_varyings(struct gl_context *ctx,
@ -415,8 +511,13 @@ do_dead_builtin_varyings(struct gl_context *ctx,
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.
/* Lower the gl_FragData array to separate variables. */
if (consumer->Type == GL_FRAGMENT_SHADER) {
lower_fragdata_array(consumer->ir);
}
/* Lowering of built-in varyings has no effect with the core context and
* GLES2, because they 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