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/*
* 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"
#include "nir_builder.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.
*/
static void
split_deref_copy_instr(nir_builder *b,
nir_deref_instr *dst, nir_deref_instr *src)
{
assert(dst->type == src->type);
if (glsl_type_is_vector_or_scalar(src->type)) {
nir_copy_deref(b, dst, src);
} else if (glsl_type_is_struct(src->type)) {
for (unsigned i = 0; i < glsl_get_length(src->type); i++) {
split_deref_copy_instr(b, nir_build_deref_struct(b, dst, i),
nir_build_deref_struct(b, src, i));
}
} else {
assert(glsl_type_is_matrix(src->type) || glsl_type_is_array(src->type));
split_deref_copy_instr(b, nir_build_deref_array_wildcard(b, dst),
nir_build_deref_array_wildcard(b, src));
}
}
static bool
split_var_copies_impl(nir_function_impl *impl)
{
bool progress = false;
nir_builder b;
nir_builder_init(&b, impl);
nir_foreach_block(block, impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *copy = nir_instr_as_intrinsic(instr);
if (copy->intrinsic != nir_intrinsic_copy_deref)
continue;
b.cursor = nir_instr_remove(©->instr);
nir_deref_instr *dst =
nir_instr_as_deref(copy->src[0].ssa->parent_instr);
nir_deref_instr *src =
nir_instr_as_deref(copy->src[1].ssa->parent_instr);
split_deref_copy_instr(&b, dst, src);
progress = true;
}
}
if (progress) {
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
}
return progress;
}
bool
nir_split_var_copies(nir_shader *shader)
{
bool progress = false;
nir_assert_unlowered_derefs(shader, nir_lower_load_store_derefs);
nir_foreach_function(function, shader) {
if (function->impl)
progress = split_var_copies_impl(function->impl) || progress;
}
return progress;
}
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