diff options
Diffstat (limited to 'src/glsl/nir/nir_control_flow.c')
| -rw-r--r-- | src/glsl/nir/nir_control_flow.c | 769 |
1 files changed, 769 insertions, 0 deletions
diff --git a/src/glsl/nir/nir_control_flow.c b/src/glsl/nir/nir_control_flow.c new file mode 100644 index 00000000000..5c03375ac77 --- /dev/null +++ b/src/glsl/nir/nir_control_flow.c @@ -0,0 +1,769 @@ +/* + * 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: + * Connor Abbott ([email protected]) + * + */ + +#include "nir_control_flow_private.h" + +/** + * \name Control flow modification + * + * These functions modify the control flow tree while keeping the control flow + * graph up-to-date. The invariants respected are: + * 1. Each then statement, else statement, or loop body must have at least one + * control flow node. + * 2. Each if-statement and loop must have one basic block before it and one + * after. + * 3. Two basic blocks cannot be directly next to each other. + * 4. If a basic block has a jump instruction, there must be only one and it + * must be at the end of the block. + * 5. The CFG must always be connected - this means that we must insert a fake + * CFG edge for loops with no break statement. + * + * The purpose of the second one is so that we have places to insert code during + * GCM, as well as eliminating the possibility of critical edges. + */ +/*@{*/ + +static bool +block_ends_in_jump(nir_block *block) +{ + return !exec_list_is_empty(&block->instr_list) && + nir_block_last_instr(block)->type == nir_instr_type_jump; +} + +static inline void +block_add_pred(nir_block *block, nir_block *pred) +{ + _mesa_set_add(block->predecessors, pred); +} + +static void +link_blocks(nir_block *pred, nir_block *succ1, nir_block *succ2) +{ + pred->successors[0] = succ1; + if (succ1 != NULL) + block_add_pred(succ1, pred); + + pred->successors[1] = succ2; + if (succ2 != NULL) + block_add_pred(succ2, pred); +} + +static void +unlink_blocks(nir_block *pred, nir_block *succ) +{ + if (pred->successors[0] == succ) { + pred->successors[0] = pred->successors[1]; + pred->successors[1] = NULL; + } else { + assert(pred->successors[1] == succ); + pred->successors[1] = NULL; + } + + struct set_entry *entry = _mesa_set_search(succ->predecessors, pred); + + assert(entry); + + _mesa_set_remove(succ->predecessors, entry); +} + +static void +unlink_block_successors(nir_block *block) +{ + if (block->successors[0] != NULL) + unlink_blocks(block, block->successors[0]); + if (block->successors[1] != NULL) + unlink_blocks(block, block->successors[1]); +} + +static void +link_non_block_to_block(nir_cf_node *node, nir_block *block) +{ + if (node->type == nir_cf_node_if) { + /* + * We're trying to link an if to a block after it; this just means linking + * the last block of the then and else branches. + */ + + nir_if *if_stmt = nir_cf_node_as_if(node); + + nir_cf_node *last_then = nir_if_last_then_node(if_stmt); + assert(last_then->type == nir_cf_node_block); + nir_block *last_then_block = nir_cf_node_as_block(last_then); + + nir_cf_node *last_else = nir_if_last_else_node(if_stmt); + assert(last_else->type == nir_cf_node_block); + nir_block *last_else_block = nir_cf_node_as_block(last_else); + + if (!block_ends_in_jump(last_then_block)) { + unlink_block_successors(last_then_block); + link_blocks(last_then_block, block, NULL); + } + + if (!block_ends_in_jump(last_else_block)) { + unlink_block_successors(last_else_block); + link_blocks(last_else_block, block, NULL); + } + } else { + assert(node->type == nir_cf_node_loop); + + /* + * We can only get to this codepath if we're inserting a new loop, or + * at least a loop with no break statements; we can't insert break + * statements into a loop when we haven't inserted it into the CFG + * because we wouldn't know which block comes after the loop + * and therefore, which block should be the successor of the block with + * the break). Therefore, we need to insert a fake edge (see invariant + * #5). + */ + + nir_loop *loop = nir_cf_node_as_loop(node); + + nir_cf_node *last = nir_loop_last_cf_node(loop); + assert(last->type == nir_cf_node_block); + nir_block *last_block = nir_cf_node_as_block(last); + + last_block->successors[1] = block; + block_add_pred(block, last_block); + } +} + +static void +link_block_to_non_block(nir_block *block, nir_cf_node *node) +{ + if (node->type == nir_cf_node_if) { + /* + * We're trying to link a block to an if after it; this just means linking + * the block to the first block of the then and else branches. + */ + + nir_if *if_stmt = nir_cf_node_as_if(node); + + nir_cf_node *first_then = nir_if_first_then_node(if_stmt); + assert(first_then->type == nir_cf_node_block); + nir_block *first_then_block = nir_cf_node_as_block(first_then); + + nir_cf_node *first_else = nir_if_first_else_node(if_stmt); + assert(first_else->type == nir_cf_node_block); + nir_block *first_else_block = nir_cf_node_as_block(first_else); + + unlink_block_successors(block); + link_blocks(block, first_then_block, first_else_block); + } else { + /* + * For similar reasons as the corresponding case in + * link_non_block_to_block(), don't worry about if the loop header has + * any predecessors that need to be unlinked. + */ + + assert(node->type == nir_cf_node_loop); + + nir_loop *loop = nir_cf_node_as_loop(node); + + nir_cf_node *loop_header = nir_loop_first_cf_node(loop); + assert(loop_header->type == nir_cf_node_block); + nir_block *loop_header_block = nir_cf_node_as_block(loop_header); + + unlink_block_successors(block); + link_blocks(block, loop_header_block, NULL); + } + +} + +/** + * Takes a basic block and inserts a new empty basic block before it, making its + * predecessors point to the new block. This essentially splits the block into + * an empty header and a body so that another non-block CF node can be inserted + * between the two. Note that this does *not* link the two basic blocks, so + * some kind of cleanup *must* be performed after this call. + */ + +static nir_block * +split_block_beginning(nir_block *block) +{ + nir_block *new_block = nir_block_create(ralloc_parent(block)); + new_block->cf_node.parent = block->cf_node.parent; + exec_node_insert_node_before(&block->cf_node.node, &new_block->cf_node.node); + + struct set_entry *entry; + set_foreach(block->predecessors, entry) { + nir_block *pred = (nir_block *) entry->key; + + unlink_blocks(pred, block); + link_blocks(pred, new_block, NULL); + } + + /* Any phi nodes must stay part of the new block, or else their + * sourcse will be messed up. This will reverse the order of the phi's, but + * order shouldn't matter. + */ + nir_foreach_instr_safe(block, instr) { + if (instr->type != nir_instr_type_phi) + break; + + exec_node_remove(&instr->node); + instr->block = new_block; + exec_list_push_head(&new_block->instr_list, &instr->node); + } + + return new_block; +} + +static void +rewrite_phi_preds(nir_block *block, nir_block *old_pred, nir_block *new_pred) +{ + nir_foreach_instr_safe(block, instr) { + if (instr->type != nir_instr_type_phi) + break; + + nir_phi_instr *phi = nir_instr_as_phi(instr); + nir_foreach_phi_src(phi, src) { + if (src->pred == old_pred) { + src->pred = new_pred; + break; + } + } + } +} + +static void +insert_phi_undef(nir_block *block, nir_block *pred) +{ + nir_function_impl *impl = nir_cf_node_get_function(&block->cf_node); + nir_foreach_instr(block, instr) { + if (instr->type != nir_instr_type_phi) + break; + + nir_phi_instr *phi = nir_instr_as_phi(instr); + nir_ssa_undef_instr *undef = + nir_ssa_undef_instr_create(ralloc_parent(phi), + phi->dest.ssa.num_components); + nir_instr_insert_before_cf_list(&impl->body, &undef->instr); + nir_phi_src *src = ralloc(phi, nir_phi_src); + src->pred = pred; + src->src.parent_instr = &phi->instr; + src->src.is_ssa = true; + src->src.ssa = &undef->def; + + list_addtail(&src->src.use_link, &undef->def.uses); + + exec_list_push_tail(&phi->srcs, &src->node); + } +} + +/** + * Moves the successors of source to the successors of dest, leaving both + * successors of source NULL. + */ + +static void +move_successors(nir_block *source, nir_block *dest) +{ + nir_block *succ1 = source->successors[0]; + nir_block *succ2 = source->successors[1]; + + if (succ1) { + unlink_blocks(source, succ1); + rewrite_phi_preds(succ1, source, dest); + } + + if (succ2) { + unlink_blocks(source, succ2); + rewrite_phi_preds(succ2, source, dest); + } + + unlink_block_successors(dest); + link_blocks(dest, succ1, succ2); +} + +/* Given a basic block with no successors that has been inserted into the + * control flow tree, gives it the successors it would normally have assuming + * it doesn't end in a jump instruction. Also inserts phi sources with undefs + * if necessary. + */ +static void +block_add_normal_succs(nir_block *block) +{ + if (exec_node_is_tail_sentinel(block->cf_node.node.next)) { + nir_cf_node *parent = block->cf_node.parent; + if (parent->type == nir_cf_node_if) { + nir_cf_node *next = nir_cf_node_next(parent); + assert(next->type == nir_cf_node_block); + nir_block *next_block = nir_cf_node_as_block(next); + + link_blocks(block, next_block, NULL); + } else { + assert(parent->type == nir_cf_node_loop); + nir_loop *loop = nir_cf_node_as_loop(parent); + + nir_cf_node *head = nir_loop_first_cf_node(loop); + assert(head->type == nir_cf_node_block); + nir_block *head_block = nir_cf_node_as_block(head); + + link_blocks(block, head_block, NULL); + insert_phi_undef(head_block, block); + } + } else { + nir_cf_node *next = nir_cf_node_next(&block->cf_node); + if (next->type == nir_cf_node_if) { + nir_if *next_if = nir_cf_node_as_if(next); + + nir_cf_node *first_then = nir_if_first_then_node(next_if); + assert(first_then->type == nir_cf_node_block); + nir_block *first_then_block = nir_cf_node_as_block(first_then); + + nir_cf_node *first_else = nir_if_first_else_node(next_if); + assert(first_else->type == nir_cf_node_block); + nir_block *first_else_block = nir_cf_node_as_block(first_else); + + link_blocks(block, first_then_block, first_else_block); + } else { + assert(next->type == nir_cf_node_loop); + nir_loop *next_loop = nir_cf_node_as_loop(next); + + nir_cf_node *first = nir_loop_first_cf_node(next_loop); + assert(first->type == nir_cf_node_block); + nir_block *first_block = nir_cf_node_as_block(first); + + link_blocks(block, first_block, NULL); + insert_phi_undef(first_block, block); + } + } +} + +static nir_block * +split_block_end(nir_block *block) +{ + nir_block *new_block = nir_block_create(ralloc_parent(block)); + new_block->cf_node.parent = block->cf_node.parent; + exec_node_insert_after(&block->cf_node.node, &new_block->cf_node.node); + + if (block_ends_in_jump(block)) { + /* Figure out what successor block would've had if it didn't have a jump + * instruction, and make new_block have that successor. + */ + block_add_normal_succs(new_block); + } else { + move_successors(block, new_block); + } + + return new_block; +} + +static nir_block * +split_block_before_instr(nir_instr *instr) +{ + assert(instr->type != nir_instr_type_phi); + nir_block *new_block = split_block_beginning(instr->block); + + nir_foreach_instr_safe(instr->block, cur_instr) { + if (cur_instr == instr) + break; + + exec_node_remove(&cur_instr->node); + cur_instr->block = new_block; + exec_list_push_tail(&new_block->instr_list, &cur_instr->node); + } + + return new_block; +} + +/* Splits a basic block at the point specified by the cursor. The "before" and + * "after" arguments are filled out with the blocks resulting from the split + * if non-NULL. Note that the "beginning" of the block is actually interpreted + * as before the first non-phi instruction, and it's illegal to split a block + * before a phi instruction. + */ + +static void +split_block_cursor(nir_cursor cursor, + nir_block **_before, nir_block **_after) +{ + nir_block *before, *after; + switch (cursor.option) { + case nir_cursor_before_block: + after = cursor.block; + before = split_block_beginning(cursor.block); + break; + + case nir_cursor_after_block: + before = cursor.block; + after = split_block_end(cursor.block); + break; + + case nir_cursor_before_instr: + after = cursor.instr->block; + before = split_block_before_instr(cursor.instr); + break; + + case nir_cursor_after_instr: + /* We lower this to split_block_before_instr() so that we can keep the + * after-a-jump-instr case contained to split_block_end(). + */ + if (nir_instr_is_last(cursor.instr)) { + before = cursor.instr->block; + after = split_block_end(cursor.instr->block); + } else { + after = cursor.instr->block; + before = split_block_before_instr(nir_instr_next(cursor.instr)); + } + break; + } + + if (_before) + *_before = before; + if (_after) + *_after = after; +} + +/** + * Inserts a non-basic block between two basic blocks and links them together. + */ + +static void +insert_non_block(nir_block *before, nir_cf_node *node, nir_block *after) +{ + node->parent = before->cf_node.parent; + exec_node_insert_after(&before->cf_node.node, &node->node); + link_block_to_non_block(before, node); + link_non_block_to_block(node, after); +} + +/* walk up the control flow tree to find the innermost enclosed loop */ +static nir_loop * +nearest_loop(nir_cf_node *node) +{ + while (node->type != nir_cf_node_loop) { + node = node->parent; + } + + return nir_cf_node_as_loop(node); +} + +/* + * update the CFG after a jump instruction has been added to the end of a block + */ + +void +nir_handle_add_jump(nir_block *block) +{ + nir_instr *instr = nir_block_last_instr(block); + nir_jump_instr *jump_instr = nir_instr_as_jump(instr); + + unlink_block_successors(block); + + nir_function_impl *impl = nir_cf_node_get_function(&block->cf_node); + nir_metadata_preserve(impl, nir_metadata_none); + + if (jump_instr->type == nir_jump_break || + jump_instr->type == nir_jump_continue) { + nir_loop *loop = nearest_loop(&block->cf_node); + + if (jump_instr->type == nir_jump_continue) { + nir_cf_node *first_node = nir_loop_first_cf_node(loop); + assert(first_node->type == nir_cf_node_block); + nir_block *first_block = nir_cf_node_as_block(first_node); + link_blocks(block, first_block, NULL); + } else { + nir_cf_node *after = nir_cf_node_next(&loop->cf_node); + assert(after->type == nir_cf_node_block); + nir_block *after_block = nir_cf_node_as_block(after); + link_blocks(block, after_block, NULL); + + /* If we inserted a fake link, remove it */ + nir_cf_node *last = nir_loop_last_cf_node(loop); + assert(last->type == nir_cf_node_block); + nir_block *last_block = nir_cf_node_as_block(last); + if (last_block->successors[1] != NULL) + unlink_blocks(last_block, after_block); + } + } else { + assert(jump_instr->type == nir_jump_return); + link_blocks(block, impl->end_block, NULL); + } +} + +static void +remove_phi_src(nir_block *block, nir_block *pred) +{ + nir_foreach_instr(block, instr) { + if (instr->type != nir_instr_type_phi) + break; + + nir_phi_instr *phi = nir_instr_as_phi(instr); + nir_foreach_phi_src_safe(phi, src) { + if (src->pred == pred) { + list_del(&src->src.use_link); + exec_node_remove(&src->node); + } + } + } +} + +/* Removes the successor of a block with a jump, and inserts a fake edge for + * infinite loops. Note that the jump to be eliminated may be free-floating. + */ + +static +void unlink_jump(nir_block *block, nir_jump_type type) +{ + if (block->successors[0]) + remove_phi_src(block->successors[0], block); + if (block->successors[1]) + remove_phi_src(block->successors[1], block); + + if (type == nir_jump_break) { + nir_block *next = block->successors[0]; + + if (next->predecessors->entries == 1) { + nir_loop *loop = + nir_cf_node_as_loop(nir_cf_node_prev(&next->cf_node)); + + /* insert fake link */ + nir_cf_node *last = nir_loop_last_cf_node(loop); + assert(last->type == nir_cf_node_block); + nir_block *last_block = nir_cf_node_as_block(last); + + last_block->successors[1] = next; + block_add_pred(next, last_block); + } + } + + unlink_block_successors(block); +} + +void +nir_handle_remove_jump(nir_block *block, nir_jump_type type) +{ + unlink_jump(block, type); + + block_add_normal_succs(block); + + nir_function_impl *impl = nir_cf_node_get_function(&block->cf_node); + nir_metadata_preserve(impl, nir_metadata_none); +} + +static void +update_if_uses(nir_cf_node *node) +{ + if (node->type != nir_cf_node_if) + return; + + nir_if *if_stmt = nir_cf_node_as_if(node); + + if_stmt->condition.parent_if = if_stmt; + if (if_stmt->condition.is_ssa) { + list_addtail(&if_stmt->condition.use_link, + &if_stmt->condition.ssa->if_uses); + } else { + list_addtail(&if_stmt->condition.use_link, + &if_stmt->condition.reg.reg->if_uses); + } +} + +/** + * Stitch two basic blocks together into one. The aggregate must have the same + * predecessors as the first and the same successors as the second. + */ + +static void +stitch_blocks(nir_block *before, nir_block *after) +{ + /* + * We move after into before, so we have to deal with up to 2 successors vs. + * possibly a large number of predecessors. + * + * TODO: special case when before is empty and after isn't? + */ + + if (block_ends_in_jump(before)) { + assert(exec_list_is_empty(&after->instr_list)); + if (after->successors[0]) + remove_phi_src(after->successors[0], after); + if (after->successors[1]) + remove_phi_src(after->successors[1], after); + unlink_block_successors(after); + exec_node_remove(&after->cf_node.node); + } else { + move_successors(after, before); + + foreach_list_typed(nir_instr, instr, node, &after->instr_list) { + instr->block = before; + } + + exec_list_append(&before->instr_list, &after->instr_list); + exec_node_remove(&after->cf_node.node); + } +} + +void +nir_cf_node_insert(nir_cursor cursor, nir_cf_node *node) +{ + nir_block *before, *after; + + split_block_cursor(cursor, &before, &after); + + if (node->type == nir_cf_node_block) { + nir_block *block = nir_cf_node_as_block(node); + exec_node_insert_after(&before->cf_node.node, &block->cf_node.node); + block->cf_node.parent = before->cf_node.parent; + /* stitch_blocks() assumes that any block that ends with a jump has + * already been setup with the correct successors, so we need to set + * up jumps here as the block is being inserted. + */ + if (block_ends_in_jump(block)) + nir_handle_add_jump(block); + + stitch_blocks(block, after); + stitch_blocks(before, block); + } else { + update_if_uses(node); + insert_non_block(before, node, after); + } +} + +static bool +replace_ssa_def_uses(nir_ssa_def *def, void *void_impl) +{ + nir_function_impl *impl = void_impl; + void *mem_ctx = ralloc_parent(impl); + + nir_ssa_undef_instr *undef = + nir_ssa_undef_instr_create(mem_ctx, def->num_components); + nir_instr_insert_before_cf_list(&impl->body, &undef->instr); + nir_ssa_def_rewrite_uses(def, nir_src_for_ssa(&undef->def), mem_ctx); + return true; +} + +static void +cleanup_cf_node(nir_cf_node *node, nir_function_impl *impl) +{ + switch (node->type) { + case nir_cf_node_block: { + nir_block *block = nir_cf_node_as_block(node); + /* We need to walk the instructions and clean up defs/uses */ + nir_foreach_instr_safe(block, instr) { + if (instr->type == nir_instr_type_jump) { + nir_jump_type jump_type = nir_instr_as_jump(instr)->type; + unlink_jump(block, jump_type); + } else { + nir_foreach_ssa_def(instr, replace_ssa_def_uses, impl); + nir_instr_remove(instr); + } + } + break; + } + + case nir_cf_node_if: { + nir_if *if_stmt = nir_cf_node_as_if(node); + foreach_list_typed(nir_cf_node, child, node, &if_stmt->then_list) + cleanup_cf_node(child, impl); + foreach_list_typed(nir_cf_node, child, node, &if_stmt->else_list) + cleanup_cf_node(child, impl); + + list_del(&if_stmt->condition.use_link); + break; + } + + case nir_cf_node_loop: { + nir_loop *loop = nir_cf_node_as_loop(node); + foreach_list_typed(nir_cf_node, child, node, &loop->body) + cleanup_cf_node(child, impl); + break; + } + case nir_cf_node_function: { + nir_function_impl *impl = nir_cf_node_as_function(node); + foreach_list_typed(nir_cf_node, child, node, &impl->body) + cleanup_cf_node(child, impl); + break; + } + default: + unreachable("Invalid CF node type"); + } +} + +void +nir_cf_extract(nir_cf_list *extracted, nir_cursor begin, nir_cursor end) +{ + nir_block *block_begin, *block_end, *block_before, *block_after; + + /* In the case where begin points to an instruction in some basic block and + * end points to the end of the same basic block, we rely on the fact that + * splitting on an instruction moves earlier instructions into a new basic + * block. If the later instructions were moved instead, then the end cursor + * would be pointing to the same place that begin used to point to, which + * is obviously not what we want. + */ + split_block_cursor(begin, &block_before, &block_begin); + split_block_cursor(end, &block_end, &block_after); + + extracted->impl = nir_cf_node_get_function(&block_begin->cf_node); + exec_list_make_empty(&extracted->list); + + nir_cf_node *cf_node = &block_begin->cf_node; + nir_cf_node *cf_node_end = &block_end->cf_node; + while (true) { + nir_cf_node *next = nir_cf_node_next(cf_node); + + exec_node_remove(&cf_node->node); + cf_node->parent = NULL; + exec_list_push_tail(&extracted->list, &cf_node->node); + + if (cf_node == cf_node_end) + break; + + cf_node = next; + } + + stitch_blocks(block_before, block_after); +} + +void +nir_cf_reinsert(nir_cf_list *cf_list, nir_cursor cursor) +{ + nir_block *before, *after; + + split_block_cursor(cursor, &before, &after); + + foreach_list_typed_safe(nir_cf_node, node, node, &cf_list->list) { + exec_node_remove(&node->node); + node->parent = before->cf_node.parent; + exec_node_insert_node_before(&after->cf_node.node, &node->node); + } + + stitch_blocks(before, + nir_cf_node_as_block(nir_cf_node_next(&before->cf_node))); + stitch_blocks(nir_cf_node_as_block(nir_cf_node_prev(&after->cf_node)), + after); +} + +void +nir_cf_delete(nir_cf_list *cf_list) +{ + foreach_list_typed(nir_cf_node, node, node, &cf_list->list) { + cleanup_cf_node(node, cf_list->impl); + } +} |