/*
* 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).
*
* This lowering pass also packs flat floats, ints, and uints together, by
* using ivec4 as the base type of flat "varyings", and using appropriate
* casts to convert floats and uints into ints.
*
* This lowering pass also handles varyings whose type is a struct or an array
* of struct. Structs are packed in order and with no gaps, so there may be a
* performance penalty due to structure elements being double-parked.
*/
#include "glsl_symbol_table.h"
#include "ir.h"
#include "ir_optimization.h"
/**
* Visitor that performs varying 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:
lower_packed_varyings_visitor(void *mem_ctx, unsigned location_base,
unsigned locations_used,
ir_variable_mode mode,
exec_list *main_instructions);
void run(exec_list *instructions);
private:
ir_assignment *bitwise_assign_pack(ir_rvalue *lhs, ir_rvalue *rhs);
ir_assignment *bitwise_assign_unpack(ir_rvalue *lhs, ir_rvalue *rhs);
unsigned lower_rvalue(ir_rvalue *rvalue, unsigned fine_location,
ir_variable *unpacked_var, const char *name);
unsigned lower_arraylike(ir_rvalue *rvalue, unsigned array_size,
unsigned fine_location,
ir_variable *unpacked_var, const char *name);
ir_variable *get_packed_varying(unsigned location,
ir_variable *unpacked_var,
const char *name);
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. VARYING_SLOT_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_shader_in or ir_var_shader_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)
{
}
void
lower_packed_varyings_visitor::run(exec_list *instructions)
{
foreach_list (node, instructions) {
ir_variable *var = ((ir_instruction *) node)->as_variable();
if (var == NULL)
continue;
if (var->mode != this->mode ||
var->location < (int) this->location_base ||
!this->needs_lowering(var))
continue;
/* This lowering pass is only capable of packing floats and ints
* together when their interpolation mode is "flat". Therefore, to be
* safe, caller should ensure that integral varyings always use flat
* interpolation, even when this is not required by GLSL.
*/
assert(var->interpolation == INTERP_QUALIFIER_FLAT ||
!var->type->contains_integer());
/* 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,
var->name);
}
}
/**
* Make an ir_assignment from \c rhs to \c lhs, performing appropriate
* bitcasts if necessary to match up types.
*
* This function is called when packing varyings.
*/
ir_assignment *
lower_packed_varyings_visitor::bitwise_assign_pack(ir_rvalue *lhs,
ir_rvalue *rhs)
{
if (lhs->type->base_type != rhs->type->base_type) {
/* Since we only mix types in flat varyings, and we always store flat
* varyings as type ivec4, we need only produce conversions from (uint
* or float) to int.
*/
assert(lhs->type->base_type == GLSL_TYPE_INT);
switch (rhs->type->base_type) {
case GLSL_TYPE_UINT:
rhs = new(this->mem_ctx)
ir_expression(ir_unop_u2i, lhs->type, rhs);
break;
case GLSL_TYPE_FLOAT:
rhs = new(this->mem_ctx)
ir_expression(ir_unop_bitcast_f2i, lhs->type, rhs);
break;
default:
assert(!"Unexpected type conversion while lowering varyings");
break;
}
}
return new(this->mem_ctx) ir_assignment(lhs, rhs);
}
/**
* Make an ir_assignment from \c rhs to \c lhs, performing appropriate
* bitcasts if necessary to match up types.
*
* This function is called when unpacking varyings.
*/
ir_assignment *
lower_packed_varyings_visitor::bitwise_assign_unpack(ir_rvalue *lhs,
ir_rvalue *rhs)
{
if (lhs->type->base_type != rhs->type->base_type) {
/* Since we only mix types in flat varyings, and we always store flat
* varyings as type ivec4, we need only produce conversions from int to
* (uint or float).
*/
assert(rhs->type->base_type == GLSL_TYPE_INT);
switch (lhs->type->base_type) {
case GLSL_TYPE_UINT:
rhs = new(this->mem_ctx)
ir_expression(ir_unop_i2u, lhs->type, rhs);
break;
case GLSL_TYPE_FLOAT:
rhs = new(this->mem_ctx)
ir_expression(ir_unop_bitcast_i2f, lhs->type, rhs);
break;
default:
assert(!"Unexpected type conversion while lowering varyings");
break;
}
}
return new(this->mem_ctx) ir_assignment(lhs, rhs);
}
/**
* 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,
const char *name)
{
if (rvalue->type->is_record()) {
for (unsigned i = 0; i < rvalue->type->length; i++) {
if (i != 0)
rvalue = rvalue->clone(this->mem_ctx, NULL);
const char *field_name = rvalue->type->fields.structure[i].name;
ir_dereference_record *dereference_record = new(this->mem_ctx)
ir_dereference_record(rvalue, field_name);
char *deref_name
= ralloc_asprintf(this->mem_ctx, "%s.%s", name, field_name);
fine_location = this->lower_rvalue(dereference_record, fine_location,
unpacked_var, deref_name);
}
return fine_location;
} else 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, name);
} 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, name);
} 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 };
char left_swizzle_name[4] = { 0, 0, 0, 0 };
char right_swizzle_name[4] = { 0, 0, 0, 0 };
for (unsigned i = 0; i < left_components; i++) {
left_swizzle_values[i] = i;
left_swizzle_name[i] = "xyzw"[i];
}
for (unsigned i = 0; i < right_components; i++) {
right_swizzle_values[i] = i + left_components;
right_swizzle_name[i] = "xyzw"[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);
char *left_name
= ralloc_asprintf(this->mem_ctx, "%s.%s", name, left_swizzle_name);
char *right_name
= ralloc_asprintf(this->mem_ctx, "%s.%s", name, right_swizzle_name);
fine_location = this->lower_rvalue(left_swizzle, fine_location,
unpacked_var, left_name);
return this->lower_rvalue(right_swizzle, fine_location, unpacked_var,
right_name);
} 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, name));
ir_swizzle *swizzle = new(this->mem_ctx)
ir_swizzle(packed_deref, swizzle_values, components);
if (this->mode == ir_var_shader_out) {
ir_assignment *assignment
= this->bitwise_assign_pack(swizzle, rvalue);
this->main_instructions->push_tail(assignment);
} else {
ir_assignment *assignment
= this->bitwise_assign_unpack(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,
const char *name)
{
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);
char *subscripted_name
= ralloc_asprintf(this->mem_ctx, "%s[%d]", name, i);
fine_location = this->lower_rvalue(dereference_array, fine_location,
unpacked_var, subscripted_name);
}
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 interpolation parameters from \c
* unpacked_var. Its base type is ivec4 if we are lowering a flat varying,
* vec4 otherwise.
*/
ir_variable *
lower_packed_varyings_visitor::get_packed_varying(unsigned location,
ir_variable *unpacked_var,
const char *name)
{
unsigned slot = location - this->location_base;
assert(slot < locations_used);
if (this->packed_varyings[slot] == NULL) {
char *packed_name = ralloc_asprintf(this->mem_ctx, "packed:%s", name);
const glsl_type *packed_type;
if (unpacked_var->interpolation == INTERP_QUALIFIER_FLAT)
packed_type = glsl_type::ivec4_type;
else
packed_type = glsl_type::vec4_type;
ir_variable *packed_var = new(this->mem_ctx)
ir_variable(packed_type, packed_name, this->mode);
packed_var->centroid = unpacked_var->centroid;
packed_var->interpolation = unpacked_var->interpolation;
packed_var->location = location;
unpacked_var->insert_before(packed_var);
this->packed_varyings[slot] = packed_var;
} else {
ralloc_asprintf_append((char **) &this->packed_varyings[slot]->name,
",%s", name);
}
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);
}