[Mesa-dev] [PATCH 08/10] glsl: Add a lowering pass for packing varyings.
Paul Berry
stereotype441 at gmail.com
Tue Dec 11 15:09:14 PST 2012
This lowering pass generates GLSL code that manually packs varyings
into vec4 slots, for the benefit of back-ends that don't support
packed varyings natively.
No functional change--the lowering pass is not yet used.
---
src/glsl/Makefile.sources | 1 +
src/glsl/ir_optimization.h | 3 +
src/glsl/lower_packed_varyings.cpp | 371 +++++++++++++++++++++++++++++++++++++
3 files changed, 375 insertions(+)
create mode 100644 src/glsl/lower_packed_varyings.cpp
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 5e098fc..d984c5c 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -57,6 +57,7 @@ LIBGLSL_FILES = \
$(GLSL_SRCDIR)/lower_jumps.cpp \
$(GLSL_SRCDIR)/lower_mat_op_to_vec.cpp \
$(GLSL_SRCDIR)/lower_noise.cpp \
+ $(GLSL_SRCDIR)/lower_packed_varyings.cpp \
$(GLSL_SRCDIR)/lower_texture_projection.cpp \
$(GLSL_SRCDIR)/lower_variable_index_to_cond_assign.cpp \
$(GLSL_SRCDIR)/lower_vec_index_to_cond_assign.cpp \
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index 628096e..6b95191 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -75,6 +75,9 @@ bool lower_quadop_vector(exec_list *instructions, bool dont_lower_swz);
bool lower_clip_distance(gl_shader *shader);
void lower_output_reads(exec_list *instructions);
void lower_ubo_reference(struct gl_shader *shader, exec_list *instructions);
+void lower_packed_varyings(void *mem_ctx, unsigned location_base,
+ unsigned locations_used, ir_variable_mode mode,
+ gl_shader *shader);
bool optimize_redundant_jumps(exec_list *instructions);
bool optimize_split_arrays(exec_list *instructions, bool linked);
diff --git a/src/glsl/lower_packed_varyings.cpp b/src/glsl/lower_packed_varyings.cpp
new file mode 100644
index 0000000..4cb9066
--- /dev/null
+++ b/src/glsl/lower_packed_varyings.cpp
@@ -0,0 +1,371 @@
+/*
+ * Copyright © 2011 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 lower_varyings_to_packed.cpp
+ *
+ * This lowering pass generates GLSL code that manually packs varyings into
+ * vec4 slots, for the benefit of back-ends that don't support packed varyings
+ * natively.
+ *
+ * For example, the following shader:
+ *
+ * out mat3x2 foo; // location=4, location_frac=0
+ * out vec3 bar[2]; // location=5, location_frac=2
+ *
+ * main()
+ * {
+ * ...
+ * }
+ *
+ * Is rewritten to:
+ *
+ * mat3x2 foo;
+ * vec3 bar[2];
+ * out vec4 packed4; // location=4, location_frac=0
+ * out vec4 packed5; // location=5, location_frac=0
+ * out vec4 packed6; // location=6, location_frac=0
+ *
+ * main()
+ * {
+ * ...
+ * packed4.xy = foo[0];
+ * packed4.zw = foo[1];
+ * packed5.xy = foo[2];
+ * packed5.zw = bar[0].xy;
+ * packed6.x = bar[0].z;
+ * packed6.yzw = bar[1];
+ * }
+ *
+ * This lowering pass properly handles "double parking" of a varying vector
+ * across two varying slots. For example, in the code above, two of the
+ * components of bar[0] are stored in packed5, and the remaining component is
+ * stored in packed6.
+ *
+ * Note that in theory, the extra instructions may cause some loss of
+ * performance. However, hopefully in most cases the performance loss will
+ * either be absorbed by a later optimization pass, or it will be offset by
+ * memory bandwidth savings (because fewer varyings are used).
+ */
+
+#include "glsl_symbol_table.h"
+#include "ir.h"
+#include "ir_optimization.h"
+
+/**
+ * Visitor that performs lowering packing. For each varying declared in the
+ * shader, this visitor determines whether it needs to be packed. If so, it
+ * demotes it to an ordinary global, creates new packed varyings, and
+ * generates assignments to convert between the original varying and the
+ * packed varying.
+ */
+class lower_packed_varyings_visitor : public ir_hierarchical_visitor
+{
+public:
+ lower_packed_varyings_visitor(void *mem_ctx, unsigned location_base,
+ unsigned locations_used,
+ ir_variable_mode mode,
+ exec_list *main_instructions);
+
+ virtual ir_visitor_status visit(ir_variable *var);
+ virtual ir_visitor_status visit_enter(ir_function *);
+
+private:
+ unsigned lower_rvalue(ir_rvalue *rvalue, unsigned fine_location,
+ ir_variable *unpacked_var);
+ unsigned lower_arraylike(ir_rvalue *rvalue, unsigned array_size,
+ unsigned fine_location,
+ ir_variable *unpacked_var);
+ ir_variable *get_packed_varying(unsigned location,
+ ir_variable *unpacked_var);
+ bool needs_lowering(ir_variable *var);
+
+ /**
+ * Memory context used to allocate new instructions for the shader.
+ */
+ void * const mem_ctx;
+
+ /**
+ * Location representing the first generic varying slot for this shader
+ * stage (e.g. VERT_RESULT_VAR0 if we are packing vertex shader outputs).
+ * Varyings whose location is less than this value are assumed to
+ * correspond to special fixed function hardware, so they are not lowered.
+ */
+ const unsigned location_base;
+
+ /**
+ * Number of generic varying slots which are used by this shader. This is
+ * used to allocate temporary intermediate data structures. If any any
+ * varying used by this shader has a location greater than or equal to
+ * location_base + locations_used, an assertion will fire.
+ */
+ const unsigned locations_used;
+
+ /**
+ * Array of pointers to the packed varyings that have been created for each
+ * generic varying slot. NULL entries in this array indicate varying slots
+ * for which a packed varying has not been created yet.
+ */
+ ir_variable **packed_varyings;
+
+ /**
+ * Type of varying which is being lowered in this pass (either ir_var_in or
+ * ir_var_out).
+ */
+ const ir_variable_mode mode;
+
+ /**
+ * List of instructions corresponding to the main() function. This is
+ * where we add instructions to pack or unpack the varyings.
+ */
+ exec_list *main_instructions;
+};
+
+lower_packed_varyings_visitor::lower_packed_varyings_visitor(
+ void *mem_ctx, unsigned location_base, unsigned locations_used,
+ ir_variable_mode mode, exec_list *main_instructions)
+ : mem_ctx(mem_ctx),
+ location_base(location_base),
+ locations_used(locations_used),
+ packed_varyings((ir_variable **)
+ rzalloc_array_size(mem_ctx, sizeof(*packed_varyings),
+ locations_used)),
+ mode(mode),
+ main_instructions(main_instructions)
+{
+}
+
+ir_visitor_status
+lower_packed_varyings_visitor::visit(ir_variable *var)
+{
+ if (var->mode != this->mode ||
+ var->location < (int) this->location_base ||
+ !this->needs_lowering(var))
+ return visit_continue;
+
+ /* Change the old varying into an ordinary global. */
+ var->mode = ir_var_auto;
+
+ /* Create a reference to the old varying. */
+ ir_dereference_variable *deref
+ = new(this->mem_ctx) ir_dereference_variable(var);
+
+ /* Recursively pack or unpack it. */
+ this->lower_rvalue(deref, var->location * 4 + var->location_frac, var);
+
+ return visit_continue;
+}
+
+ir_visitor_status
+lower_packed_varyings_visitor::visit_enter(ir_function *)
+{
+ /* No need to recurse into functions, since all the variable declarations
+ * we need to look at are at top level.
+ */
+ return visit_continue_with_parent;
+}
+
+/**
+ * Recursively pack or unpack the given varying (or portion of a varying) by
+ * traversing all of its constituent vectors.
+ *
+ * \param fine_location is the location where the first constituent vector
+ * should be packed--the word "fine" indicates that this location is expressed
+ * in multiples of a float, rather than multiples of a vec4 as is used
+ * elsewhere in Mesa.
+ *
+ * \return the location where the next constituent vector (after this one)
+ * should be packed.
+ */
+unsigned
+lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
+ unsigned fine_location,
+ ir_variable *unpacked_var)
+{
+ /* FINISHME: Support for "varying" records in GLSL 1.50. */
+ assert(!rvalue->type->is_record());
+
+ if (rvalue->type->is_array()) {
+ /* Arrays are packed/unpacked by considering each array element in
+ * sequence.
+ */
+ return this->lower_arraylike(rvalue, rvalue->type->array_size(),
+ fine_location, unpacked_var);
+ } else if (rvalue->type->is_matrix()) {
+ /* Matrices are packed/unpacked by considering each column vector in
+ * sequence.
+ */
+ return this->lower_arraylike(rvalue, rvalue->type->matrix_columns,
+ fine_location, unpacked_var);
+ } else if (rvalue->type->vector_elements + fine_location % 4 > 4) {
+ /* This vector is going to be "double parked" across two varying slots,
+ * so handle it as two separate assignments.
+ */
+ unsigned left_components = 4 - fine_location % 4;
+ unsigned right_components
+ = rvalue->type->vector_elements - left_components;
+ unsigned left_swizzle_values[4] = { 0, 0, 0, 0 };
+ unsigned right_swizzle_values[4] = { 0, 0, 0, 0 };
+ for (unsigned i = 0; i < left_components; i++)
+ left_swizzle_values[i] = i;
+ for (unsigned i = 0; i < right_components; i++)
+ right_swizzle_values[i] = i + left_components;
+ ir_swizzle *left_swizzle = new(this->mem_ctx)
+ ir_swizzle(rvalue, left_swizzle_values, left_components);
+ ir_swizzle *right_swizzle = new(this->mem_ctx)
+ ir_swizzle(rvalue->clone(this->mem_ctx, NULL), right_swizzle_values,
+ right_components);
+ fine_location = this->lower_rvalue(left_swizzle, fine_location,
+ unpacked_var);
+ return this->lower_rvalue(right_swizzle, fine_location, unpacked_var);
+ } else {
+ /* No special handling is necessary; pack the rvalue into the
+ * varying.
+ */
+ unsigned swizzle_values[4] = { 0, 0, 0, 0 };
+ unsigned components = rvalue->type->vector_elements;
+ unsigned location = fine_location / 4;
+ unsigned location_frac = fine_location % 4;
+ for (unsigned i = 0; i < components; ++i)
+ swizzle_values[i] = i + location_frac;
+ ir_dereference_variable *packed_deref = new(this->mem_ctx)
+ ir_dereference_variable(this->get_packed_varying(location,
+ unpacked_var));
+ ir_swizzle *swizzle = new(this->mem_ctx)
+ ir_swizzle(packed_deref, swizzle_values, components);
+ if (this->mode == ir_var_out) {
+ ir_assignment *assignment = new(this->mem_ctx)
+ ir_assignment(swizzle, rvalue);
+ this->main_instructions->push_tail(assignment);
+ } else {
+ ir_assignment *assignment = new(this->mem_ctx)
+ ir_assignment(rvalue, swizzle);
+ this->main_instructions->push_head(assignment);
+ }
+ return fine_location + components;
+ }
+}
+
+/**
+ * Recursively pack or unpack a varying for which we need to iterate over its
+ * constituent elements, accessing each one using an ir_dereference_array.
+ * This takes care of both arrays and matrices, since ir_dereference_array
+ * treats a matrix like an array of its column vectors.
+ */
+unsigned
+lower_packed_varyings_visitor::lower_arraylike(ir_rvalue *rvalue,
+ unsigned array_size,
+ unsigned fine_location,
+ ir_variable *unpacked_var)
+{
+ for (unsigned i = 0; i < array_size; i++) {
+ if (i != 0)
+ rvalue = rvalue->clone(this->mem_ctx, NULL);
+ ir_constant *constant = new(this->mem_ctx) ir_constant(i);
+ ir_dereference_array *dereference_array = new(this->mem_ctx)
+ ir_dereference_array(rvalue, constant);
+ fine_location = this->lower_rvalue(dereference_array, fine_location,
+ unpacked_var);
+ }
+ return fine_location;
+}
+
+/**
+ * Retrieve the packed varying corresponding to the given varying location.
+ * If no packed varying has been created for the given varying location yet,
+ * create it and add it to the shader before returning it.
+ *
+ * The newly created varying inherits its base type (float, uint, or int) and
+ * interpolation parameters from \c unpacked_var.
+ */
+ir_variable *
+lower_packed_varyings_visitor::get_packed_varying(unsigned location,
+ ir_variable *unpacked_var)
+{
+ unsigned slot = location - this->location_base;
+ assert(slot < locations_used);
+ if (this->packed_varyings[slot] == NULL) {
+ char name[10];
+ sprintf(name, "packed%d", slot);
+ const glsl_type *packed_type;
+ switch (unpacked_var->type->get_scalar_type()->base_type) {
+ case GLSL_TYPE_UINT:
+ packed_type = glsl_type::uvec4_type;
+ break;
+ case GLSL_TYPE_INT:
+ packed_type = glsl_type::ivec4_type;
+ break;
+ case GLSL_TYPE_FLOAT:
+ packed_type = glsl_type::vec4_type;
+ break;
+ case GLSL_TYPE_BOOL:
+ /* Note: in theory bools aren't supposed to be allowed to be
+ * varyings, however Mesa doesn't know to reject them yet. Until
+ * this is fixed, we might as well allow them to be packed too.
+ */
+ packed_type = glsl_type::bvec4_type;
+ break;
+ default:
+ assert(!"Unexpected varying type while packing");
+ packed_type = glsl_type::vec4_type;
+ break;
+ }
+ ir_variable *packed_var = new(this->mem_ctx)
+ ir_variable(packed_type, name, this->mode);
+ packed_var->centroid = unpacked_var->centroid;
+ packed_var->interpolation = unpacked_var->interpolation;
+ packed_var->location = location;
+ this->base_ir->insert_before(packed_var);
+ this->packed_varyings[slot] = packed_var;
+ }
+ return this->packed_varyings[slot];
+}
+
+bool
+lower_packed_varyings_visitor::needs_lowering(ir_variable *var)
+{
+ /* Things composed of vec4's don't need lowering. Everything else does. */
+ const glsl_type *type = var->type;
+ if (type->is_array())
+ type = type->fields.array;
+ if (type->vector_elements == 4)
+ return false;
+ return true;
+}
+
+void
+lower_packed_varyings(void *mem_ctx, unsigned location_base,
+ unsigned locations_used, ir_variable_mode mode,
+ gl_shader *shader)
+{
+ exec_list *instructions = shader->ir;
+ ir_function *main_func = shader->symbols->get_function("main");
+ exec_list void_parameters;
+ ir_function_signature *main_func_sig
+ = main_func->matching_signature(&void_parameters);
+ exec_list *main_instructions = &main_func_sig->body;
+ lower_packed_varyings_visitor visitor(mem_ctx, location_base,
+ locations_used, mode,
+ main_instructions);
+ visitor.run(instructions);
+}
--
1.8.0.1
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