142 lines
5.5 KiB
C
142 lines
5.5 KiB
C
/*
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* Copyright © 2014 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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* Authors:
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* Jason Ekstrand (jason@jlekstrand.net)
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*
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*/
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#include "nir.h"
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#include "nir_builder.h"
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/*
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* Implements "copy splitting" which is similar to structure splitting only
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* it works on copy operations rather than the datatypes themselves. The
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* GLSL language allows you to copy one variable to another an entire
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* structure (which may contain arrays or other structures) at a time.
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* Normally, in a language such as C this would be handled by a "structure
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* splitting" pass that breaks up the structures. Unfortunately for us,
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* structures used in inputs or outputs can't be split. Therefore,
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* regardlesss of what we do, we have to be able to copy to/from
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* structures.
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*
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* The primary purpose of structure splitting is to allow you to better
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* optimize variable access and lower things to registers where you can.
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* The primary issue here is that, if you lower the copy to a bunch of
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* loads and stores, you loose a lot of information about the copy
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* operation that you would like to keep around. To solve this problem, we
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* have a "copy splitting" pass that, instead of splitting the structures
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* or lowering the copy into loads and storres, splits the copy operation
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* into a bunch of copy operations one for each leaf of the structure tree.
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* If an intermediate array is encountered, it is referenced with a
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* wildcard reference to indicate that the entire array is to be copied.
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*
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* As things become direct, array copies may be able to be losslessly
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* lowered to having fewer and fewer wildcards. However, until that
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* happens we want to keep the information about the arrays intact.
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*
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* Prior to the copy splitting pass, there are no wildcard references but
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* there may be incomplete references where the tail of the deref chain is
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* an array or a structure and not a specific element. After the copy
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* splitting pass has completed, every variable deref will be a full-length
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* dereference pointing to a single leaf in the structure type tree with
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* possibly a few wildcard array dereferences.
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*/
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static void
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split_deref_copy_instr(nir_builder *b,
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nir_deref_instr *dst, nir_deref_instr *src,
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enum gl_access_qualifier dst_access,
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enum gl_access_qualifier src_access)
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{
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assert(glsl_get_bare_type(dst->type) ==
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glsl_get_bare_type(src->type));
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if (glsl_type_is_vector_or_scalar(src->type)) {
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nir_copy_deref_with_access(b, dst, src, dst_access, src_access);
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} else if (glsl_type_is_struct_or_ifc(src->type)) {
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for (unsigned i = 0; i < glsl_get_length(src->type); i++) {
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split_deref_copy_instr(b, nir_build_deref_struct(b, dst, i),
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nir_build_deref_struct(b, src, i),
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dst_access, src_access);
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}
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} else {
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assert(glsl_type_is_matrix(src->type) || glsl_type_is_array(src->type));
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split_deref_copy_instr(b, nir_build_deref_array_wildcard(b, dst),
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nir_build_deref_array_wildcard(b, src),
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dst_access, src_access);
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}
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}
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static bool
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split_var_copies_impl(nir_function_impl *impl)
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{
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bool progress = false;
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nir_builder b;
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nir_builder_init(&b, impl);
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nir_foreach_block(block, impl) {
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nir_foreach_instr_safe(instr, block) {
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if (instr->type != nir_instr_type_intrinsic)
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continue;
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nir_intrinsic_instr *copy = nir_instr_as_intrinsic(instr);
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if (copy->intrinsic != nir_intrinsic_copy_deref)
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continue;
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b.cursor = nir_instr_remove(©->instr);
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nir_deref_instr *dst =
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nir_instr_as_deref(copy->src[0].ssa->parent_instr);
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nir_deref_instr *src =
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nir_instr_as_deref(copy->src[1].ssa->parent_instr);
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split_deref_copy_instr(&b, dst, src,
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nir_intrinsic_dst_access(copy),
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nir_intrinsic_src_access(copy));
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progress = true;
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}
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}
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if (progress) {
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nir_metadata_preserve(impl, nir_metadata_block_index |
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nir_metadata_dominance);
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} else {
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nir_metadata_preserve(impl, nir_metadata_all);
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}
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return progress;
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}
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bool
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nir_split_var_copies(nir_shader *shader)
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{
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bool progress = false;
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nir_foreach_function(function, shader) {
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if (function->impl)
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progress = split_var_copies_impl(function->impl) || progress;
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}
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return progress;
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}
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