/*
* Copyright © 2010 Luca Barbieri
*
* 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_variable_index_to_cond_assign.cpp
*
* Turns non-constant indexing into array types to a series of
* conditional moves of each element into a temporary.
*
* Pre-DX10 GPUs often don't have a native way to do this operation,
* and this works around that.
*
* The lowering process proceeds as follows. Each non-constant index
* found in an r-value is converted to a canonical form \c array[i]. Each
* element of the array is conditionally assigned to a temporary by comparing
* \c i to a constant index. This is done by cloning the canonical form and
* replacing all occurances of \c i with a constant. Each remaining occurance
* of the canonical form in the IR is replaced with a dereference of the
* temporary variable.
*
* L-values with non-constant indices are handled similarly. In this case,
* the RHS of the assignment is assigned to a temporary. The non-constant
* index is replace with the canonical form (just like for r-values). The
* temporary is conditionally assigned to each element of the canonical form
* by comparing \c i with each index. The same clone-and-replace scheme is
* used.
*/
#include "ir.h"
#include "ir_rvalue_visitor.h"
#include "ir_optimization.h"
#include "glsl_types.h"
#include "main/macros.h"
/**
* Generate a comparison value for a block of indices
*
* Lowering passes for non-constant indexing of arrays, matrices, or vectors
* can use this to generate blocks of index comparison values.
*
* \param instructions List where new instructions will be appended
* \param index \c ir_variable containing the desired index
* \param base Base value for this block of comparisons
* \param components Number of unique index values to compare. This must
* be on the range [1, 4].
* \param mem_ctx ralloc memory context to be used for all allocations.
*
* \returns
* An \c ir_rvalue that \b must be cloned for each use in conditional
* assignments, etc.
*/
ir_rvalue *
compare_index_block(exec_list *instructions, ir_variable *index,
unsigned base, unsigned components, void *mem_ctx)
{
ir_rvalue *broadcast_index = new(mem_ctx) ir_dereference_variable(index);
assert(index->type->is_scalar());
assert(index->type->base_type == GLSL_TYPE_INT || index->type->base_type == GLSL_TYPE_UINT);
assert(components >= 1 && components <= 4);
if (components > 1) {
const ir_swizzle_mask m = { 0, 0, 0, 0, components, false };
broadcast_index = new(mem_ctx) ir_swizzle(broadcast_index, m);
}
/* Compare the desired index value with the next block of four indices.
*/
ir_constant_data test_indices_data;
memset(&test_indices_data, 0, sizeof(test_indices_data));
test_indices_data.i[0] = base;
test_indices_data.i[1] = base + 1;
test_indices_data.i[2] = base + 2;
test_indices_data.i[3] = base + 3;
ir_constant *const test_indices =
new(mem_ctx) ir_constant(broadcast_index->type,
&test_indices_data);
ir_rvalue *const condition_val =
new(mem_ctx) ir_expression(ir_binop_equal,
glsl_type::bvec(components),
broadcast_index,
test_indices);
ir_variable *const condition =
new(mem_ctx) ir_variable(condition_val->type,
"dereference_condition",
ir_var_temporary);
instructions->push_tail(condition);
ir_rvalue *const cond_deref =
new(mem_ctx) ir_dereference_variable(condition);
instructions->push_tail(new(mem_ctx) ir_assignment(cond_deref, condition_val, 0));
return cond_deref;
}
static inline bool
is_array_or_matrix(const ir_rvalue *ir)
{
return (ir->type->is_array() || ir->type->is_matrix());
}
namespace {
/**
* Replace a dereference of a variable with a specified r-value
*
* Each time a dereference of the specified value is replaced, the r-value
* tree is cloned.
*/
class deref_replacer : public ir_rvalue_visitor {
public:
deref_replacer(const ir_variable *variable_to_replace, ir_rvalue *value)
: variable_to_replace(variable_to_replace), value(value),
progress(false)
{
assert(this->variable_to_replace != NULL);
assert(this->value != NULL);
}
virtual void handle_rvalue(ir_rvalue **rvalue)
{
ir_dereference_variable *const dv = (*rvalue)->as_dereference_variable();
if ((dv != NULL) && (dv->var == this->variable_to_replace)) {
this->progress = true;
*rvalue = this->value->clone(ralloc_parent(*rvalue), NULL);
}
}
const ir_variable *variable_to_replace;
ir_rvalue *value;
bool progress;
};
/**
* Find a variable index dereference of an array in an rvalue tree
*/
class find_variable_index : public ir_hierarchical_visitor {
public:
find_variable_index()
: deref(NULL)
{
/* empty */
}
virtual ir_visitor_status visit_enter(ir_dereference_array *ir)
{
if (is_array_or_matrix(ir->array)
&& (ir->array_index->as_constant() == NULL)) {
this->deref = ir;
return visit_stop;
}
return visit_continue;
}
/**
* First array dereference found in the tree that has a non-constant index.
*/
ir_dereference_array *deref;
};
struct assignment_generator
{
ir_instruction* base_ir;
ir_dereference *rvalue;
ir_variable *old_index;
bool is_write;
unsigned int write_mask;
ir_variable* var;
assignment_generator()
: base_ir(NULL),
rvalue(NULL),
old_index(NULL),
is_write(false),
write_mask(0),
var(NULL)
{
}
void generate(unsigned i, ir_rvalue* condition, exec_list *list) const
{
/* Just clone the rest of the deref chain when trying to get at the
* underlying variable.
*/
void *mem_ctx = ralloc_parent(base_ir);
/* Clone the old r-value in its entirety. Then replace any occurances of
* the old variable index with the new constant index.
*/
ir_dereference *element = this->rvalue->clone(mem_ctx, NULL);
ir_constant *const index = new(mem_ctx) ir_constant(i);
deref_replacer r(this->old_index, index);
element->accept(&r);
assert(r.progress);
/* Generate a conditional assignment to (or from) the constant indexed
* array dereference.
*/
ir_rvalue *variable = new(mem_ctx) ir_dereference_variable(this->var);
ir_assignment *const assignment = (is_write)
? new(mem_ctx) ir_assignment(element, variable, condition, write_mask)
: new(mem_ctx) ir_assignment(variable, element, condition);
list->push_tail(assignment);
}
};
struct switch_generator
{
/* make TFunction a template parameter if you need to use other generators */
typedef assignment_generator TFunction;
const TFunction& generator;
ir_variable* index;
unsigned linear_sequence_max_length;
unsigned condition_components;
void *mem_ctx;
switch_generator(const TFunction& generator, ir_variable *index,
unsigned linear_sequence_max_length,
unsigned condition_components)
: generator(generator), index(index),
linear_sequence_max_length(linear_sequence_max_length),
condition_components(condition_components)
{
this->mem_ctx = ralloc_parent(index);
}
void linear_sequence(unsigned begin, unsigned end, exec_list *list)
{
if (begin == end)
return;
/* If the array access is a read, read the first element of this subregion
* unconditionally. The remaining tests will possibly overwrite this
* value with one of the other array elements.
*
* This optimization cannot be done for writes because it will cause the
* first element of the subregion to be written possibly *in addition* to
* one of the other elements.
*/
unsigned first;
if (!this->generator.is_write) {
this->generator.generate(begin, 0, list);
first = begin + 1;
} else {
first = begin;
}
for (unsigned i = first; i < end; i += 4) {
const unsigned comps = MIN2(condition_components, end - i);
ir_rvalue *const cond_deref =
compare_index_block(list, index, i, comps, this->mem_ctx);
if (comps == 1) {
this->generator.generate(i, cond_deref->clone(this->mem_ctx, NULL),
list);
} else {
for (unsigned j = 0; j < comps; j++) {
ir_rvalue *const cond_swiz =
new(this->mem_ctx) ir_swizzle(cond_deref->clone(this->mem_ctx, NULL),
j, 0, 0, 0, 1);
this->generator.generate(i + j, cond_swiz, list);
}
}
}
}
void bisect(unsigned begin, unsigned end, exec_list *list)
{
unsigned middle = (begin + end) >> 1;
assert(index->type->is_integer());
ir_constant *const middle_c = (index->type->base_type == GLSL_TYPE_UINT)
? new(this->mem_ctx) ir_constant((unsigned)middle)
: new(this->mem_ctx) ir_constant((int)middle);
ir_dereference_variable *deref =
new(this->mem_ctx) ir_dereference_variable(this->index);
ir_expression *less =
new(this->mem_ctx) ir_expression(ir_binop_less, glsl_type::bool_type,
deref, middle_c);
ir_if *if_less = new(this->mem_ctx) ir_if(less);
generate(begin, middle, &if_less->then_instructions);
generate(middle, end, &if_less->else_instructions);
list->push_tail(if_less);
}
void generate(unsigned begin, unsigned end, exec_list *list)
{
unsigned length = end - begin;
if (length <= this->linear_sequence_max_length)
return linear_sequence(begin, end, list);
else
return bisect(begin, end, list);
}
};
/**
* Visitor class for replacing expressions with ir_constant values.
*/
class variable_index_to_cond_assign_visitor : public ir_rvalue_visitor {
public:
variable_index_to_cond_assign_visitor(bool lower_input,
bool lower_output,
bool lower_temp,
bool lower_uniform)
{
this->progress = false;
this->lower_inputs = lower_input;
this->lower_outputs = lower_output;
this->lower_temps = lower_temp;
this->lower_uniforms = lower_uniform;
}
bool progress;
bool lower_inputs;
bool lower_outputs;
bool lower_temps;
bool lower_uniforms;
bool storage_type_needs_lowering(ir_dereference_array *deref) const
{
/* If a variable isn't eventually the target of this dereference, then
* it must be a constant or some sort of anonymous temporary storage.
*
* FINISHME: Is this correct? Most drivers treat arrays of constants as
* FINISHME: uniforms. It seems like this should do the same.
*/
const ir_variable *const var = deref->array->variable_referenced();
if (var == NULL)
return this->lower_temps;
switch (var->data.mode) {
case ir_var_auto:
case ir_var_temporary:
return this->lower_temps;
case ir_var_uniform:
return this->lower_uniforms;
case ir_var_function_in:
case ir_var_const_in:
return this->lower_temps;
case ir_var_shader_in:
return this->lower_inputs;
case ir_var_function_out:
return this->lower_temps;
case ir_var_shader_out:
return this->lower_outputs;
case ir_var_function_inout:
return this->lower_temps;
}
assert(!"Should not get here.");
return false;
}
bool needs_lowering(ir_dereference_array *deref) const
{
if (deref == NULL || deref->array_index->as_constant()
|| !is_array_or_matrix(deref->array))
return false;
return this->storage_type_needs_lowering(deref);
}
ir_variable *convert_dereference_array(ir_dereference_array *orig_deref,
ir_assignment* orig_assign,
ir_dereference *orig_base)
{
assert(is_array_or_matrix(orig_deref->array));
const unsigned length = (orig_deref->array->type->is_array())
? orig_deref->array->type->length
: orig_deref->array->type->matrix_columns;
void *const mem_ctx = ralloc_parent(base_ir);
/* Temporary storage for either the result of the dereference of
* the array, or the RHS that's being assigned into the
* dereference of the array.
*/
ir_variable *var;
if (orig_assign) {
var = new(mem_ctx) ir_variable(orig_assign->rhs->type,
"dereference_array_value",
ir_var_temporary);
base_ir->insert_before(var);
ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(var);
ir_assignment *assign = new(mem_ctx) ir_assignment(lhs,
orig_assign->rhs,
NULL);
base_ir->insert_before(assign);
} else {
var = new(mem_ctx) ir_variable(orig_deref->type,
"dereference_array_value",
ir_var_temporary);
base_ir->insert_before(var);
}
/* Store the index to a temporary to avoid reusing its tree. */
ir_variable *index =
new(mem_ctx) ir_variable(orig_deref->array_index->type,
"dereference_array_index", ir_var_temporary);
base_ir->insert_before(index);
ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(index);
ir_assignment *assign =
new(mem_ctx) ir_assignment(lhs, orig_deref->array_index, NULL);
base_ir->insert_before(assign);
orig_deref->array_index = lhs->clone(mem_ctx, NULL);
assignment_generator ag;
ag.rvalue = orig_base;
ag.base_ir = base_ir;
ag.old_index = index;
ag.var = var;
if (orig_assign) {
ag.is_write = true;
ag.write_mask = orig_assign->write_mask;
} else {
ag.is_write = false;
}
switch_generator sg(ag, index, 4, 4);
/* If the original assignment has a condition, respect that original
* condition! This is acomplished by wrapping the new conditional
* assignments in an if-statement that uses the original condition.
*/
if ((orig_assign != NULL) && (orig_assign->condition != NULL)) {
/* No need to clone the condition because the IR that it hangs on is
* going to be removed from the instruction sequence.
*/
ir_if *if_stmt = new(mem_ctx) ir_if(orig_assign->condition);
sg.generate(0, length, &if_stmt->then_instructions);
base_ir->insert_before(if_stmt);
} else {
exec_list list;
sg.generate(0, length, &list);
base_ir->insert_before(&list);
}
return var;
}
virtual void handle_rvalue(ir_rvalue **pir)
{
if (this->in_assignee)
return;
if (!*pir)
return;
ir_dereference_array* orig_deref = (*pir)->as_dereference_array();
if (needs_lowering(orig_deref)) {
ir_variable *var =
convert_dereference_array(orig_deref, NULL, orig_deref);
assert(var);
*pir = new(ralloc_parent(base_ir)) ir_dereference_variable(var);
this->progress = true;
}
}
ir_visitor_status
visit_leave(ir_assignment *ir)
{
ir_rvalue_visitor::visit_leave(ir);
find_variable_index f;
ir->lhs->accept(&f);
if ((f.deref != NULL) && storage_type_needs_lowering(f.deref)) {
convert_dereference_array(f.deref, ir, ir->lhs);
ir->remove();
this->progress = true;
}
return visit_continue;
}
};
} /* anonymous namespace */
bool
lower_variable_index_to_cond_assign(exec_list *instructions,
bool lower_input,
bool lower_output,
bool lower_temp,
bool lower_uniform)
{
variable_index_to_cond_assign_visitor v(lower_input,
lower_output,
lower_temp,
lower_uniform);
/* Continue lowering until no progress is made. If there are multiple
* levels of indirection (e.g., non-constant indexing of array elements and
* matrix columns of an array of matrix), each pass will only lower one
* level of indirection.
*/
bool progress_ever = false;
do {
v.progress = false;
visit_list_elements(&v, instructions);
progress_ever = v.progress || progress_ever;
} while (v.progress);
return progress_ever;
}