/*
* Copyright © 2014 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.
*
* Authors:
* Jason Ekstrand (jason@jlekstrand.net)
*
*/
#include "nir.h"
/*
* Implements "copy splitting" which is similar to structure splitting only
* it works on copy operations rather than the datatypes themselves. The
* GLSL language allows you to copy one variable to another an entire
* structure (which may contain arrays or other structures) at a time.
* Normally, in a language such as C this would be handled by a "structure
* splitting" pass that breaks up the structures. Unfortunately for us,
* structures used in inputs or outputs can't be split. Therefore,
* regardlesss of what we do, we have to be able to copy to/from
* structures.
*
* The primary purpose of structure splitting is to allow you to better
* optimize variable access and lower things to registers where you can.
* The primary issue here is that, if you lower the copy to a bunch of
* loads and stores, you loose a lot of information about the copy
* operation that you would like to keep around. To solve this problem, we
* have a "copy splitting" pass that, instead of splitting the structures
* or lowering the copy into loads and storres, splits the copy operation
* into a bunch of copy operations one for each leaf of the structure tree.
* If an intermediate array is encountered, it is referenced with a
* wildcard reference to indicate that the entire array is to be copied.
*
* As things become direct, array copies may be able to be losslessly
* lowered to having fewer and fewer wildcards. However, until that
* happens we want to keep the information about the arrays intact.
*
* Prior to the copy splitting pass, there are no wildcard references but
* there may be incomplete references where the tail of the deref chain is
* an array or a structure and not a specific element. After the copy
* splitting pass has completed, every variable deref will be a full-length
* dereference pointing to a single leaf in the structure type tree with
* possibly a few wildcard array dereferences.
*/
struct split_var_copies_state {
void *mem_ctx;
void *dead_ctx;
};
static nir_deref *
get_deref_tail(nir_deref *deref)
{
while (deref->child != NULL)
deref = deref->child;
return deref;
}
/* Recursively constructs deref chains to split a copy instruction into
* multiple (if needed) copy instructions with full-length deref chains.
* External callers of this function should pass the tail and head of the
* deref chains found as the source and destination of the copy instruction
* into this function.
*
* \param old_copy The copy instruction we are splitting
* \param dest_head The head of the destination deref chain we are building
* \param src_head The head of the source deref chain we are building
* \param dest_tail The tail of the destination deref chain we are building
* \param src_tail The tail of the source deref chain we are building
* \param state The current split_var_copies_state object
*/
static void
split_var_copy_instr(nir_intrinsic_instr *old_copy,
nir_deref *dest_head, nir_deref *src_head,
nir_deref *dest_tail, nir_deref *src_tail,
struct split_var_copies_state *state)
{
assert(src_tail
->type
== dest_tail
->type
);
/* Make sure these really are the tails of the deref chains */
assert(dest_tail
->child
== NULL
); assert(src_tail
->child
== NULL
);
switch (glsl_get_base_type(src_tail->type)) {
case GLSL_TYPE_ARRAY: {
/* Make a wildcard dereference */
nir_deref_array *deref = nir_deref_array_create(state->dead_ctx);
deref->deref.type = glsl_get_array_element(src_tail->type);
deref->deref_array_type = nir_deref_array_type_wildcard;
/* Set the tail of both as the newly created wildcard deref. It is
* safe to use the same wildcard in both places because a) we will be
* copying it before we put it in an actual instruction and b)
* everything that will potentially add another link in the deref
* chain will also add the same thing to both chains.
*/
src_tail->child = &deref->deref;
dest_tail->child = &deref->deref;
split_var_copy_instr(old_copy, dest_head, src_head,
dest_tail->child, src_tail->child, state);
/* Set it back to the way we found it */
src_tail->child = NULL;
dest_tail->child = NULL;
break;
}
case GLSL_TYPE_STRUCT:
/* This is the only part that actually does any interesting
* splitting. For array types, we just use wildcards and resolve
* them later. For structure types, we need to emit one copy
* instruction for every structure element. Because we may have
* structs inside structs, we just recurse and let the next level
* take care of any additional structures.
*/
for (unsigned i = 0; i < glsl_get_length(src_tail->type); i++) {
nir_deref_struct *deref = nir_deref_struct_create(state->dead_ctx, i);
deref->deref.type = glsl_get_struct_field(src_tail->type, i);
/* Set the tail of both as the newly created structure deref. It
* is safe to use the same wildcard in both places because a) we
* will be copying it before we put it in an actual instruction
* and b) everything that will potentially add another link in the
* deref chain will also add the same thing to both chains.
*/
src_tail->child = &deref->deref;
dest_tail->child = &deref->deref;
split_var_copy_instr(old_copy, dest_head, src_head,
dest_tail->child, src_tail->child, state);
}
/* Set it back to the way we found it */
src_tail->child = NULL;
dest_tail->child = NULL;
break;
case GLSL_TYPE_UINT:
case GLSL_TYPE_INT:
case GLSL_TYPE_FLOAT:
case GLSL_TYPE_BOOL:
if (glsl_type_is_matrix(src_tail->type)) {
nir_deref_array *deref = nir_deref_array_create(state->dead_ctx);
deref->deref.type = glsl_get_column_type(src_tail->type);
deref->deref_array_type = nir_deref_array_type_wildcard;
/* Set the tail of both as the newly created wildcard deref. It
* is safe to use the same wildcard in both places because a) we
* will be copying it before we put it in an actual instruction
* and b) everything that will potentially add another link in the
* deref chain will also add the same thing to both chains.
*/
src_tail->child = &deref->deref;
dest_tail->child = &deref->deref;
split_var_copy_instr(old_copy, dest_head, src_head,
dest_tail->child, src_tail->child, state);
/* Set it back to the way we found it */
src_tail->child = NULL;
dest_tail->child = NULL;
} else {
/* At this point, we have fully built our deref chains and can
* actually add the new copy instruction.
*/
nir_intrinsic_instr *new_copy =
nir_intrinsic_instr_create(state->mem_ctx, nir_intrinsic_copy_var);
/* We need to make copies because a) this deref chain actually
* belongs to the copy instruction and b) the deref chains may
* have some of the same links due to the way we constructed them
*/
nir_deref *src = nir_copy_deref(new_copy, src_head);
nir_deref *dest = nir_copy_deref(new_copy, dest_head);
new_copy->variables[0] = nir_deref_as_var(dest);
new_copy->variables[1] = nir_deref_as_var(src);
/* Emit the copy instruction after the old instruction. We'll
* remove the old one later.
*/
nir_instr_insert_after(&old_copy->instr, &new_copy->instr);
}
break;
case GLSL_TYPE_SAMPLER:
case GLSL_TYPE_IMAGE:
case GLSL_TYPE_ATOMIC_UINT:
case GLSL_TYPE_INTERFACE:
default:
unreachable("Cannot copy these types");
}
}
static bool
split_var_copies_block(nir_block *block, void *void_state)
{
struct split_var_copies_state *state = void_state;
nir_foreach_instr_safe(block, instr) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intrinsic = nir_instr_as_intrinsic(instr);
if (intrinsic->intrinsic != nir_intrinsic_copy_var)
continue;
nir_deref *dest_head = &intrinsic->variables[0]->deref;
nir_deref *src_head = &intrinsic->variables[1]->deref;
nir_deref *dest_tail = get_deref_tail(dest_head);
nir_deref *src_tail = get_deref_tail(src_head);
switch (glsl_get_base_type(src_tail->type)) {
case GLSL_TYPE_ARRAY:
case GLSL_TYPE_STRUCT:
split_var_copy_instr(intrinsic, dest_head, src_head,
dest_tail, src_tail, state);
nir_instr_remove(&intrinsic->instr);
ralloc_steal(state->dead_ctx, instr);
break;
case GLSL_TYPE_FLOAT:
case GLSL_TYPE_INT:
case GLSL_TYPE_UINT:
case GLSL_TYPE_BOOL:
if (glsl_type_is_matrix(src_tail->type)) {
split_var_copy_instr(intrinsic, dest_head, src_head,
dest_tail, src_tail, state);
nir_instr_remove(&intrinsic->instr);
ralloc_steal(state->dead_ctx, instr);
}
break;
default:
unreachable("Invalid type");
break;
}
}
return true;
}
static void
split_var_copies_impl(nir_function_impl *impl)
{
struct split_var_copies_state state;
state.mem_ctx = ralloc_parent(impl);
state.dead_ctx = ralloc_context(NULL);
nir_foreach_block(impl, split_var_copies_block, &state);
ralloc_free(state.dead_ctx);
}
void
nir_split_var_copies(nir_shader *shader)
{
nir_foreach_overload(shader, overload) {
if (overload->impl)
split_var_copies_impl(overload->impl);
}
}