286 lines
11 KiB
C
286 lines
11 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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/*
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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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struct split_var_copies_state {
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void *mem_ctx;
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void *dead_ctx;
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bool progress;
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};
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/* Recursively constructs deref chains to split a copy instruction into
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* multiple (if needed) copy instructions with full-length deref chains.
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* External callers of this function should pass the tail and head of the
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* deref chains found as the source and destination of the copy instruction
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* into this function.
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*
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* \param old_copy The copy instruction we are splitting
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* \param dest_head The head of the destination deref chain we are building
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* \param src_head The head of the source deref chain we are building
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* \param dest_tail The tail of the destination deref chain we are building
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* \param src_tail The tail of the source deref chain we are building
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* \param state The current split_var_copies_state object
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*/
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static void
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split_var_copy_instr(nir_intrinsic_instr *old_copy,
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nir_deref *dest_head, nir_deref *src_head,
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nir_deref *dest_tail, nir_deref *src_tail,
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struct split_var_copies_state *state)
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{
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assert(src_tail->type == dest_tail->type);
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/* Make sure these really are the tails of the deref chains */
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assert(dest_tail->child == NULL);
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assert(src_tail->child == NULL);
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switch (glsl_get_base_type(src_tail->type)) {
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case GLSL_TYPE_ARRAY: {
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/* Make a wildcard dereference */
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nir_deref_array *deref = nir_deref_array_create(state->dead_ctx);
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deref->deref.type = glsl_get_array_element(src_tail->type);
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deref->deref_array_type = nir_deref_array_type_wildcard;
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/* Set the tail of both as the newly created wildcard deref. It is
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* safe to use the same wildcard in both places because a) we will be
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* copying it before we put it in an actual instruction and b)
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* everything that will potentially add another link in the deref
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* chain will also add the same thing to both chains.
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*/
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src_tail->child = &deref->deref;
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dest_tail->child = &deref->deref;
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split_var_copy_instr(old_copy, dest_head, src_head,
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dest_tail->child, src_tail->child, state);
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/* Set it back to the way we found it */
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src_tail->child = NULL;
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dest_tail->child = NULL;
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break;
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}
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case GLSL_TYPE_STRUCT:
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/* This is the only part that actually does any interesting
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* splitting. For array types, we just use wildcards and resolve
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* them later. For structure types, we need to emit one copy
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* instruction for every structure element. Because we may have
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* structs inside structs, we just recurse and let the next level
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* take care of any additional structures.
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*/
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for (unsigned i = 0; i < glsl_get_length(src_tail->type); i++) {
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nir_deref_struct *deref = nir_deref_struct_create(state->dead_ctx, i);
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deref->deref.type = glsl_get_struct_field(src_tail->type, i);
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/* Set the tail of both as the newly created structure deref. It
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* is safe to use the same wildcard in both places because a) we
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* will be copying it before we put it in an actual instruction
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* and b) everything that will potentially add another link in the
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* deref chain will also add the same thing to both chains.
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*/
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src_tail->child = &deref->deref;
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dest_tail->child = &deref->deref;
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split_var_copy_instr(old_copy, dest_head, src_head,
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dest_tail->child, src_tail->child, state);
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}
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/* Set it back to the way we found it */
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src_tail->child = NULL;
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dest_tail->child = NULL;
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break;
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case GLSL_TYPE_UINT:
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case GLSL_TYPE_INT:
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case GLSL_TYPE_FLOAT:
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case GLSL_TYPE_BOOL:
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if (glsl_type_is_matrix(src_tail->type)) {
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nir_deref_array *deref = nir_deref_array_create(state->dead_ctx);
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deref->deref.type = glsl_get_column_type(src_tail->type);
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deref->deref_array_type = nir_deref_array_type_wildcard;
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/* Set the tail of both as the newly created wildcard deref. It
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* is safe to use the same wildcard in both places because a) we
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* will be copying it before we put it in an actual instruction
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* and b) everything that will potentially add another link in the
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* deref chain will also add the same thing to both chains.
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*/
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src_tail->child = &deref->deref;
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dest_tail->child = &deref->deref;
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split_var_copy_instr(old_copy, dest_head, src_head,
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dest_tail->child, src_tail->child, state);
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/* Set it back to the way we found it */
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src_tail->child = NULL;
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dest_tail->child = NULL;
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} else {
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/* At this point, we have fully built our deref chains and can
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* actually add the new copy instruction.
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*/
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nir_intrinsic_instr *new_copy =
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nir_intrinsic_instr_create(state->mem_ctx, nir_intrinsic_copy_var);
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/* We need to make copies because a) this deref chain actually
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* belongs to the copy instruction and b) the deref chains may
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* have some of the same links due to the way we constructed them
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*/
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nir_deref *src = nir_copy_deref(new_copy, src_head);
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nir_deref *dest = nir_copy_deref(new_copy, dest_head);
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new_copy->variables[0] = nir_deref_as_var(dest);
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new_copy->variables[1] = nir_deref_as_var(src);
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/* Emit the copy instruction after the old instruction. We'll
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* remove the old one later.
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*/
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nir_instr_insert_after(&old_copy->instr, &new_copy->instr);
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state->progress = true;
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}
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break;
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case GLSL_TYPE_SAMPLER:
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case GLSL_TYPE_IMAGE:
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case GLSL_TYPE_ATOMIC_UINT:
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case GLSL_TYPE_INTERFACE:
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default:
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unreachable("Cannot copy these types");
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}
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}
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static bool
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split_var_copies_block(nir_block *block, void *void_state)
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{
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struct split_var_copies_state *state = void_state;
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nir_foreach_instr_safe(block, instr) {
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if (instr->type != nir_instr_type_intrinsic)
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continue;
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nir_intrinsic_instr *intrinsic = nir_instr_as_intrinsic(instr);
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if (intrinsic->intrinsic != nir_intrinsic_copy_var)
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continue;
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nir_deref *dest_head = &intrinsic->variables[0]->deref;
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nir_deref *src_head = &intrinsic->variables[1]->deref;
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nir_deref *dest_tail = nir_deref_tail(dest_head);
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nir_deref *src_tail = nir_deref_tail(src_head);
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switch (glsl_get_base_type(src_tail->type)) {
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case GLSL_TYPE_ARRAY:
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case GLSL_TYPE_STRUCT:
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split_var_copy_instr(intrinsic, dest_head, src_head,
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dest_tail, src_tail, state);
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nir_instr_remove(&intrinsic->instr);
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ralloc_steal(state->dead_ctx, instr);
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break;
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case GLSL_TYPE_FLOAT:
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case GLSL_TYPE_INT:
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case GLSL_TYPE_UINT:
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case GLSL_TYPE_BOOL:
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if (glsl_type_is_matrix(src_tail->type)) {
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split_var_copy_instr(intrinsic, dest_head, src_head,
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dest_tail, src_tail, state);
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nir_instr_remove(&intrinsic->instr);
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ralloc_steal(state->dead_ctx, instr);
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}
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break;
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default:
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unreachable("Invalid type");
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break;
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}
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}
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return true;
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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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struct split_var_copies_state state;
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state.mem_ctx = ralloc_parent(impl);
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state.dead_ctx = ralloc_context(NULL);
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state.progress = false;
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nir_foreach_block(impl, split_var_copies_block, &state);
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ralloc_free(state.dead_ctx);
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if (state.progress) {
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nir_metadata_preserve(impl, nir_metadata_block_index |
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nir_metadata_dominance);
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}
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return state.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(shader, function) {
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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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