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Diffstat (limited to 'src/compiler/nir/nir_split_var_copies.c')
| -rw-r--r-- | src/compiler/nir/nir_split_var_copies.c | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/src/compiler/nir/nir_split_var_copies.c b/src/compiler/nir/nir_split_var_copies.c new file mode 100644 index 0000000..6fdaefa --- /dev/null +++ b/src/compiler/nir/nir_split_var_copies.c @@ -0,0 +1,285 @@ +/* + * 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; + bool progress; +}; + +/* 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); + state->progress = true; + } + 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 = nir_deref_tail(dest_head); + nir_deref *src_tail = nir_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 bool +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); + state.progress = false; + + nir_foreach_block(impl, split_var_copies_block, &state); + + ralloc_free(state.dead_ctx); + + if (state.progress) { + nir_metadata_preserve(impl, nir_metadata_block_index | + nir_metadata_dominance); + } + + return state.progress; +} + +bool +nir_split_var_copies(nir_shader *shader) +{ + bool progress = false; + + nir_foreach_function(shader, function) { + if (function->impl) + progress = split_var_copies_impl(function->impl) || progress; + } + + return progress; +} |