--- /dev/null
+/*
+ * 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;
+};
+
+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);
+
+ if (old_copy->has_predicate) {
+ new_copy->has_predicate = true;
+ new_copy->predicate = nir_src_copy(old_copy->predicate,
+ state->mem_ctx);
+ }
+
+ /* 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(state->mem_ctx, src_head);
+ nir_deref *dest = nir_copy_deref(state->mem_ctx, 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);
+ }
+ 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 void
+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);
+
+ nir_foreach_block(impl, split_var_copies_block, &state);
+
+ ralloc_free(state.dead_ctx);
+}
+
+void
+nir_split_var_copies(nir_shader *shader)
+{
+ nir_foreach_overload(shader, overload) {
+ if (overload->impl)
+ split_var_copies_impl(overload->impl);
+ }
+}
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