--- /dev/null
+/*
+ * 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);
+ }
+}
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