/* * Copyright © 2018 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. */ #include "nir.h" #include "nir_builder.h" #include "nir_deref.h" #include "util/hash_table.h" void nir_deref_path_init(nir_deref_path *path, nir_deref_instr *deref, void *mem_ctx) { assert(deref != NULL); /* The length of the short path is at most ARRAY_SIZE - 1 because we need * room for the NULL terminator. */ static const int max_short_path_len = ARRAY_SIZE(path->_short_path) - 1; int count = 0; nir_deref_instr **tail = &path->_short_path[max_short_path_len]; nir_deref_instr **head = tail; *tail = NULL; for (nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) { count++; if (count <= max_short_path_len) *(--head) = d; } if (count <= max_short_path_len) { /* If we're under max_short_path_len, just use the short path. */ path->path = head; goto done; } #ifndef NDEBUG /* Just in case someone uses short_path by accident */ for (unsigned i = 0; i < ARRAY_SIZE(path->_short_path); i++) path->_short_path[i] = (void *)0xdeadbeef; #endif path->path = ralloc_array(mem_ctx, nir_deref_instr *, count + 1); head = tail = path->path + count; *tail = NULL; for (nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) *(--head) = d; done: assert(head == path->path); assert(tail == head + count); assert(*tail == NULL); } void nir_deref_path_finish(nir_deref_path *path) { if (path->path < &path->_short_path[0] || path->path > &path->_short_path[ARRAY_SIZE(path->_short_path) - 1]) ralloc_free(path->path); } /** * Recursively removes unused deref instructions */ bool nir_deref_instr_remove_if_unused(nir_deref_instr *instr) { bool progress = false; for (nir_deref_instr *d = instr; d; d = nir_deref_instr_parent(d)) { /* If anyone is using this deref, leave it alone */ assert(d->dest.is_ssa); if (!list_empty(&d->dest.ssa.uses)) break; nir_instr_remove(&d->instr); progress = true; } return progress; } bool nir_deref_instr_has_indirect(nir_deref_instr *instr) { while (instr->deref_type != nir_deref_type_var) { /* Consider casts to be indirects */ if (instr->deref_type == nir_deref_type_cast) return true; if ((instr->deref_type == nir_deref_type_array || instr->deref_type == nir_deref_type_ptr_as_array) && !nir_src_is_const(instr->arr.index)) return true; instr = nir_deref_instr_parent(instr); } return false; } unsigned nir_deref_instr_ptr_as_array_stride(nir_deref_instr *deref) { assert(deref->deref_type == nir_deref_type_ptr_as_array); nir_deref_instr *parent = nir_deref_instr_parent(deref); switch (parent->deref_type) { case nir_deref_type_array: return glsl_get_explicit_stride(nir_deref_instr_parent(parent)->type); case nir_deref_type_ptr_as_array: return nir_deref_instr_ptr_as_array_stride(parent); case nir_deref_type_cast: return parent->cast.ptr_stride; default: unreachable("Invalid parent for ptr_as_array deref"); } } static unsigned type_get_array_stride(const struct glsl_type *elem_type, glsl_type_size_align_func size_align) { unsigned elem_size, elem_align; size_align(elem_type, &elem_size, &elem_align); return ALIGN_POT(elem_size, elem_align); } static unsigned struct_type_get_field_offset(const struct glsl_type *struct_type, glsl_type_size_align_func size_align, unsigned field_idx) { assert(glsl_type_is_struct_or_ifc(struct_type)); unsigned offset = 0; for (unsigned i = 0; i <= field_idx; i++) { unsigned elem_size, elem_align; size_align(glsl_get_struct_field(struct_type, i), &elem_size, &elem_align); offset = ALIGN_POT(offset, elem_align); if (i < field_idx) offset += elem_size; } return offset; } unsigned nir_deref_instr_get_const_offset(nir_deref_instr *deref, glsl_type_size_align_func size_align) { nir_deref_path path; nir_deref_path_init(&path, deref, NULL); assert(path.path[0]->deref_type == nir_deref_type_var); unsigned offset = 0; for (nir_deref_instr **p = &path.path[1]; *p; p++) { if ((*p)->deref_type == nir_deref_type_array) { offset += nir_src_as_uint((*p)->arr.index) * type_get_array_stride((*p)->type, size_align); } else if ((*p)->deref_type == nir_deref_type_struct) { /* p starts at path[1], so this is safe */ nir_deref_instr *parent = *(p - 1); offset += struct_type_get_field_offset(parent->type, size_align, (*p)->strct.index); } else { unreachable("Unsupported deref type"); } } nir_deref_path_finish(&path); return offset; } nir_ssa_def * nir_build_deref_offset(nir_builder *b, nir_deref_instr *deref, glsl_type_size_align_func size_align) { nir_deref_path path; nir_deref_path_init(&path, deref, NULL); assert(path.path[0]->deref_type == nir_deref_type_var); nir_ssa_def *offset = nir_imm_int(b, 0); for (nir_deref_instr **p = &path.path[1]; *p; p++) { if ((*p)->deref_type == nir_deref_type_array) { nir_ssa_def *index = nir_ssa_for_src(b, (*p)->arr.index, 1); int stride = type_get_array_stride((*p)->type, size_align); offset = nir_iadd(b, offset, nir_imul_imm(b, index, stride)); } else if ((*p)->deref_type == nir_deref_type_struct) { /* p starts at path[1], so this is safe */ nir_deref_instr *parent = *(p - 1); unsigned field_offset = struct_type_get_field_offset(parent->type, size_align, (*p)->strct.index); offset = nir_iadd_imm(b, offset, field_offset); } else { unreachable("Unsupported deref type"); } } nir_deref_path_finish(&path); return offset; } bool nir_remove_dead_derefs_impl(nir_function_impl *impl) { bool progress = false; nir_foreach_block(block, impl) { nir_foreach_instr_safe(instr, block) { if (instr->type == nir_instr_type_deref && nir_deref_instr_remove_if_unused(nir_instr_as_deref(instr))) progress = true; } } if (progress) nir_metadata_preserve(impl, nir_metadata_block_index | nir_metadata_dominance); return progress; } bool nir_remove_dead_derefs(nir_shader *shader) { bool progress = false; nir_foreach_function(function, shader) { if (function->impl && nir_remove_dead_derefs_impl(function->impl)) progress = true; } return progress; } void nir_fixup_deref_modes(nir_shader *shader) { nir_foreach_function(function, shader) { if (!function->impl) continue; nir_foreach_block(block, function->impl) { nir_foreach_instr(instr, block) { if (instr->type != nir_instr_type_deref) continue; nir_deref_instr *deref = nir_instr_as_deref(instr); if (deref->deref_type == nir_deref_type_cast) continue; nir_variable_mode parent_mode; if (deref->deref_type == nir_deref_type_var) { parent_mode = deref->var->data.mode; } else { assert(deref->parent.is_ssa); nir_deref_instr *parent = nir_instr_as_deref(deref->parent.ssa->parent_instr); parent_mode = parent->mode; } deref->mode = parent_mode; } } } } static bool modes_may_alias(nir_variable_mode a, nir_variable_mode b) { /* Generic pointers can alias with SSBOs */ if ((a == nir_var_mem_ssbo || a == nir_var_mem_global) && (b == nir_var_mem_ssbo || b == nir_var_mem_global)) return true; /* In the general case, pointers can only alias if they have the same mode. * * NOTE: In future, with things like OpenCL generic pointers, this may not * be true and will have to be re-evaluated. However, with graphics only, * it should be safe. */ return a == b; } static bool deref_path_contains_coherent_decoration(nir_deref_path *path) { assert(path->path[0]->deref_type == nir_deref_type_var); if (path->path[0]->var->data.image.access & ACCESS_COHERENT) return true; for (nir_deref_instr **p = &path->path[1]; *p; p++) { if ((*p)->deref_type != nir_deref_type_struct) continue; const struct glsl_type *struct_type = (*(p - 1))->type; const struct glsl_struct_field *field = glsl_get_struct_field_data(struct_type, (*p)->strct.index); if (field->memory_coherent) return true; } return false; } nir_deref_compare_result nir_compare_deref_paths(nir_deref_path *a_path, nir_deref_path *b_path) { if (!modes_may_alias(b_path->path[0]->mode, a_path->path[0]->mode)) return nir_derefs_do_not_alias; if (a_path->path[0]->deref_type != b_path->path[0]->deref_type) return nir_derefs_may_alias_bit; if (a_path->path[0]->deref_type == nir_deref_type_var) { if (a_path->path[0]->var != b_path->path[0]->var) { /* Shader and function temporaries aren't backed by memory so two * distinct variables never alias. */ static const nir_variable_mode temp_var_modes = nir_var_shader_temp | nir_var_function_temp; if ((a_path->path[0]->mode & temp_var_modes) || (b_path->path[0]->mode & temp_var_modes)) return nir_derefs_do_not_alias; /* If they are both declared coherent or have coherent somewhere in * their path (due to a member of an interface being declared * coherent), we have to assume we that we could have any kind of * aliasing. Otherwise, they could still alias but the client didn't * tell us and that's their fault. */ if (deref_path_contains_coherent_decoration(a_path) && deref_path_contains_coherent_decoration(b_path)) return nir_derefs_may_alias_bit; /* If we can chase the deref all the way back to the variable and * they're not the same variable and at least one is not declared * coherent, we know they can't possibly alias. */ return nir_derefs_do_not_alias; } } else { assert(a_path->path[0]->deref_type == nir_deref_type_cast); /* If they're not exactly the same cast, it's hard to compare them so we * just assume they alias. Comparing casts is tricky as there are lots * of things such as mode, type, etc. to make sure work out; for now, we * just assume nit_opt_deref will combine them and compare the deref * instructions. * * TODO: At some point in the future, we could be clever and understand * that a float[] and int[] have the same layout and aliasing structure * but double[] and vec3[] do not and we could potentially be a bit * smarter here. */ if (a_path->path[0] != b_path->path[0]) return nir_derefs_may_alias_bit; } /* Start off assuming they fully compare. We ignore equality for now. In * the end, we'll determine that by containment. */ nir_deref_compare_result result = nir_derefs_may_alias_bit | nir_derefs_a_contains_b_bit | nir_derefs_b_contains_a_bit; nir_deref_instr **a_p = &a_path->path[1]; nir_deref_instr **b_p = &b_path->path[1]; while (*a_p != NULL && *a_p == *b_p) { a_p++; b_p++; } /* We're at either the tail or the divergence point between the two deref * paths. Look to see if either contains a ptr_as_array deref. It it * does we don't know how to safely make any inferences. Hopefully, * nir_opt_deref will clean most of these up and we can start inferring * things again. * * In theory, we could do a bit better. For instance, we could detect the * case where we have exactly one ptr_as_array deref in the chain after the * divergence point and it's matched in both chains and the two chains have * different constant indices. */ for (nir_deref_instr **t_p = a_p; *t_p; t_p++) { if ((*t_p)->deref_type == nir_deref_type_ptr_as_array) return nir_derefs_may_alias_bit; } for (nir_deref_instr **t_p = b_p; *t_p; t_p++) { if ((*t_p)->deref_type == nir_deref_type_ptr_as_array) return nir_derefs_may_alias_bit; } while (*a_p != NULL && *b_p != NULL) { nir_deref_instr *a_tail = *(a_p++); nir_deref_instr *b_tail = *(b_p++); switch (a_tail->deref_type) { case nir_deref_type_array: case nir_deref_type_array_wildcard: { assert(b_tail->deref_type == nir_deref_type_array || b_tail->deref_type == nir_deref_type_array_wildcard); if (a_tail->deref_type == nir_deref_type_array_wildcard) { if (b_tail->deref_type != nir_deref_type_array_wildcard) result &= ~nir_derefs_b_contains_a_bit; } else if (b_tail->deref_type == nir_deref_type_array_wildcard) { if (a_tail->deref_type != nir_deref_type_array_wildcard) result &= ~nir_derefs_a_contains_b_bit; } else { assert(a_tail->deref_type == nir_deref_type_array && b_tail->deref_type == nir_deref_type_array); assert(a_tail->arr.index.is_ssa && b_tail->arr.index.is_ssa); if (nir_src_is_const(a_tail->arr.index) && nir_src_is_const(b_tail->arr.index)) { /* If they're both direct and have different offsets, they * don't even alias much less anything else. */ if (nir_src_as_uint(a_tail->arr.index) != nir_src_as_uint(b_tail->arr.index)) return nir_derefs_do_not_alias; } else if (a_tail->arr.index.ssa == b_tail->arr.index.ssa) { /* They're the same indirect, continue on */ } else { /* They're not the same index so we can't prove anything about * containment. */ result &= ~(nir_derefs_a_contains_b_bit | nir_derefs_b_contains_a_bit); } } break; } case nir_deref_type_struct: { /* If they're different struct members, they don't even alias */ if (a_tail->strct.index != b_tail->strct.index) return nir_derefs_do_not_alias; break; } default: unreachable("Invalid deref type"); } } /* If a is longer than b, then it can't contain b */ if (*a_p != NULL) result &= ~nir_derefs_a_contains_b_bit; if (*b_p != NULL) result &= ~nir_derefs_b_contains_a_bit; /* If a contains b and b contains a they must be equal. */ if ((result & nir_derefs_a_contains_b_bit) && (result & nir_derefs_b_contains_a_bit)) result |= nir_derefs_equal_bit; return result; } nir_deref_compare_result nir_compare_derefs(nir_deref_instr *a, nir_deref_instr *b) { if (a == b) { return nir_derefs_equal_bit | nir_derefs_may_alias_bit | nir_derefs_a_contains_b_bit | nir_derefs_b_contains_a_bit; } nir_deref_path a_path, b_path; nir_deref_path_init(&a_path, a, NULL); nir_deref_path_init(&b_path, b, NULL); assert(a_path.path[0]->deref_type == nir_deref_type_var || a_path.path[0]->deref_type == nir_deref_type_cast); assert(b_path.path[0]->deref_type == nir_deref_type_var || b_path.path[0]->deref_type == nir_deref_type_cast); nir_deref_compare_result result = nir_compare_deref_paths(&a_path, &b_path); nir_deref_path_finish(&a_path); nir_deref_path_finish(&b_path); return result; } struct rematerialize_deref_state { bool progress; nir_builder builder; nir_block *block; struct hash_table *cache; }; static nir_deref_instr * rematerialize_deref_in_block(nir_deref_instr *deref, struct rematerialize_deref_state *state) { if (deref->instr.block == state->block) return deref; if (!state->cache) { state->cache = _mesa_pointer_hash_table_create(NULL); } struct hash_entry *cached = _mesa_hash_table_search(state->cache, deref); if (cached) return cached->data; nir_builder *b = &state->builder; nir_deref_instr *new_deref = nir_deref_instr_create(b->shader, deref->deref_type); new_deref->mode = deref->mode; new_deref->type = deref->type; if (deref->deref_type == nir_deref_type_var) { new_deref->var = deref->var; } else { nir_deref_instr *parent = nir_src_as_deref(deref->parent); if (parent) { parent = rematerialize_deref_in_block(parent, state); new_deref->parent = nir_src_for_ssa(&parent->dest.ssa); } else { nir_src_copy(&new_deref->parent, &deref->parent, new_deref); } } switch (deref->deref_type) { case nir_deref_type_var: case nir_deref_type_array_wildcard: case nir_deref_type_cast: /* Nothing more to do */ break; case nir_deref_type_array: assert(!nir_src_as_deref(deref->arr.index)); nir_src_copy(&new_deref->arr.index, &deref->arr.index, new_deref); break; case nir_deref_type_struct: new_deref->strct.index = deref->strct.index; break; default: unreachable("Invalid deref instruction type"); } nir_ssa_dest_init(&new_deref->instr, &new_deref->dest, deref->dest.ssa.num_components, deref->dest.ssa.bit_size, deref->dest.ssa.name); nir_builder_instr_insert(b, &new_deref->instr); return new_deref; } static bool rematerialize_deref_src(nir_src *src, void *_state) { struct rematerialize_deref_state *state = _state; nir_deref_instr *deref = nir_src_as_deref(*src); if (!deref) return true; nir_deref_instr *block_deref = rematerialize_deref_in_block(deref, state); if (block_deref != deref) { nir_instr_rewrite_src(src->parent_instr, src, nir_src_for_ssa(&block_deref->dest.ssa)); nir_deref_instr_remove_if_unused(deref); state->progress = true; } return true; } /** Re-materialize derefs in every block * * This pass re-materializes deref instructions in every block in which it is * used. After this pass has been run, every use of a deref will be of a * deref in the same block as the use. Also, all unused derefs will be * deleted as a side-effect. */ bool nir_rematerialize_derefs_in_use_blocks_impl(nir_function_impl *impl) { struct rematerialize_deref_state state = { 0 }; nir_builder_init(&state.builder, impl); nir_foreach_block(block, impl) { state.block = block; /* Start each block with a fresh cache */ if (state.cache) _mesa_hash_table_clear(state.cache, NULL); nir_foreach_instr_safe(instr, block) { if (instr->type == nir_instr_type_deref && nir_deref_instr_remove_if_unused(nir_instr_as_deref(instr))) continue; state.builder.cursor = nir_before_instr(instr); nir_foreach_src(instr, rematerialize_deref_src, &state); } #ifndef NDEBUG nir_if *following_if = nir_block_get_following_if(block); if (following_if) assert(!nir_src_as_deref(following_if->condition)); #endif } _mesa_hash_table_destroy(state.cache, NULL); return state.progress; } static bool is_trivial_deref_cast(nir_deref_instr *cast) { nir_deref_instr *parent = nir_src_as_deref(cast->parent); if (!parent) return false; return cast->mode == parent->mode && cast->type == parent->type && cast->dest.ssa.num_components == parent->dest.ssa.num_components && cast->dest.ssa.bit_size == parent->dest.ssa.bit_size; } static bool is_trivial_array_deref_cast(nir_deref_instr *cast) { assert(is_trivial_deref_cast(cast)); nir_deref_instr *parent = nir_src_as_deref(cast->parent); if (parent->deref_type == nir_deref_type_array) { return cast->cast.ptr_stride == glsl_get_explicit_stride(nir_deref_instr_parent(parent)->type); } else if (parent->deref_type == nir_deref_type_ptr_as_array) { return cast->cast.ptr_stride == nir_deref_instr_ptr_as_array_stride(parent); } else { return false; } } static bool is_deref_ptr_as_array(nir_instr *instr) { return instr->type == nir_instr_type_deref && nir_instr_as_deref(instr)->deref_type == nir_deref_type_ptr_as_array; } /** * Remove casts that just wrap other casts. */ static bool opt_remove_cast_cast(nir_deref_instr *cast) { nir_deref_instr *first_cast = cast; while (true) { nir_deref_instr *parent = nir_deref_instr_parent(first_cast); if (parent == NULL || parent->deref_type != nir_deref_type_cast) break; first_cast = parent; } if (cast == first_cast) return false; nir_instr_rewrite_src(&cast->instr, &cast->parent, nir_src_for_ssa(first_cast->parent.ssa)); return true; } /** * Is this casting a struct to a contained struct. * struct a { struct b field0 }; * ssa_5 is structa; * deref_cast (structb *)ssa_5 (function_temp structb); * converts to * deref_struct &ssa_5->field0 (function_temp structb); * This allows subsequent copy propagation to work. */ static bool opt_replace_struct_wrapper_cast(nir_builder *b, nir_deref_instr *cast) { nir_deref_instr *parent = nir_src_as_deref(cast->parent); if (!parent) return false; if (!glsl_type_is_struct(parent->type)) return false; if (glsl_get_struct_field_offset(parent->type, 0) != 0) return false; if (cast->type != glsl_get_struct_field(parent->type, 0)) return false; nir_deref_instr *replace = nir_build_deref_struct(b, parent, 0); nir_ssa_def_rewrite_uses(&cast->dest.ssa, nir_src_for_ssa(&replace->dest.ssa)); nir_deref_instr_remove_if_unused(cast); return true; } static bool opt_deref_cast(nir_builder *b, nir_deref_instr *cast) { bool progress; if (opt_replace_struct_wrapper_cast(b, cast)) return true; progress = opt_remove_cast_cast(cast); if (!is_trivial_deref_cast(cast)) return progress; bool trivial_array_cast = is_trivial_array_deref_cast(cast); assert(cast->dest.is_ssa); assert(cast->parent.is_ssa); nir_foreach_use_safe(use_src, &cast->dest.ssa) { /* If this isn't a trivial array cast, we can't propagate into * ptr_as_array derefs. */ if (is_deref_ptr_as_array(use_src->parent_instr) && !trivial_array_cast) continue; nir_instr_rewrite_src(use_src->parent_instr, use_src, cast->parent); progress = true; } /* If uses would be a bit crazy */ assert(list_empty(&cast->dest.ssa.if_uses)); nir_deref_instr_remove_if_unused(cast); return progress; } static bool opt_deref_ptr_as_array(nir_builder *b, nir_deref_instr *deref) { assert(deref->deref_type == nir_deref_type_ptr_as_array); nir_deref_instr *parent = nir_deref_instr_parent(deref); if (nir_src_is_const(deref->arr.index) && nir_src_as_int(deref->arr.index) == 0) { /* If it's a ptr_as_array deref with an index of 0, it does nothing * and we can just replace its uses with its parent. * * The source of a ptr_as_array deref always has a deref_type of * nir_deref_type_array or nir_deref_type_cast. If it's a cast, it * may be trivial and we may be able to get rid of that too. Any * trivial cast of trivial cast cases should be handled already by * opt_deref_cast() above. */ if (parent->deref_type == nir_deref_type_cast && is_trivial_deref_cast(parent)) parent = nir_deref_instr_parent(parent); nir_ssa_def_rewrite_uses(&deref->dest.ssa, nir_src_for_ssa(&parent->dest.ssa)); nir_instr_remove(&deref->instr); return true; } if (parent->deref_type != nir_deref_type_array && parent->deref_type != nir_deref_type_ptr_as_array) return false; assert(parent->parent.is_ssa); assert(parent->arr.index.is_ssa); assert(deref->arr.index.is_ssa); nir_ssa_def *new_idx = nir_iadd(b, parent->arr.index.ssa, deref->arr.index.ssa); deref->deref_type = parent->deref_type; nir_instr_rewrite_src(&deref->instr, &deref->parent, parent->parent); nir_instr_rewrite_src(&deref->instr, &deref->arr.index, nir_src_for_ssa(new_idx)); return true; } bool nir_opt_deref_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_deref) continue; b.cursor = nir_before_instr(instr); nir_deref_instr *deref = nir_instr_as_deref(instr); switch (deref->deref_type) { case nir_deref_type_ptr_as_array: if (opt_deref_ptr_as_array(&b, deref)) progress = true; break; case nir_deref_type_cast: if (opt_deref_cast(&b, deref)) progress = true; break; default: /* Do nothing */ break; } } } if (progress) { nir_metadata_preserve(impl, nir_metadata_block_index | nir_metadata_dominance); } else { #ifndef NDEBUG impl->valid_metadata &= ~nir_metadata_not_properly_reset; #endif } return progress; } bool nir_opt_deref(nir_shader *shader) { bool progress = false; nir_foreach_function(func, shader) { if (func->impl && nir_opt_deref_impl(func->impl)) progress = true; } return progress; }