/* * 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; }; 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); 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 = 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 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); return state.progress; } bool nir_split_var_copies(nir_shader *shader) { bool progress = false; nir_foreach_overload(shader, overload) { if (overload->impl) progress = split_var_copies_impl(overload->impl) || progress; } return progress; }