nir: move to compiler/

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Matt Turner <mattst88@gmail.com>
Acked-by: Jose Fonseca <jfonseca@vmware.com>

1 files changed, 808 insertions, 0 deletions

diff --git a/src/compiler/nir/nir_control_flow.c b/src/compiler/nir/nir_control_flow.c
new file mode 100644
index 0000000..96395a4
--- /dev/null
+++ b/src/compiler/nir/nir_control_flow.c
@@ -0,0 +1,808 @@
+/*
+ * 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 (cwabbott0@gmail.com)
+ *
+ */
+
+#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 inline void
+block_remove_pred(nir_block *block, nir_block *pred)
+{
+   struct set_entry *entry = _mesa_set_search(block->predecessors, pred);
+
+   assert(entry);
+
+   _mesa_set_remove(block->predecessors, entry);
+}
+
+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;
+   }
+
+   block_remove_pred(succ, pred);
+}
+
+static void
+unlink_block_successors(nir_block *block)
+{
+   if (block->successors[1] != NULL)
+      unlink_blocks(block, block->successors[1]);
+   if (block->successors[0] != NULL)
+      unlink_blocks(block, block->successors[0]);
+}
+
+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);
+   }
+
+}
+
+/**
+ * Replace a block's successor with a different one.
+ */
+static void
+replace_successor(nir_block *block, nir_block *old_succ, nir_block *new_succ)
+{
+   if (block->successors[0] == old_succ) {
+      block->successors[0] = new_succ;
+   } else {
+      assert(block->successors[1] == old_succ);
+      block->successors[1] = new_succ;
+   }
+
+   block_remove_pred(old_succ, block);
+   block_add_pred(new_succ, block);
+}
+
+/**
+ * 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;
+      replace_successor(pred, block, new_block);
+   }
+
+   /* 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;
+
+   default:
+      unreachable("not reached");
+   }
+
+   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, bool add_normal_successors)
+{
+   nir_block *next = block->successors[0];
+
+   if (block->successors[0])
+      remove_phi_src(block->successors[0], block);
+   if (block->successors[1])
+      remove_phi_src(block->successors[1], block);
+
+   unlink_block_successors(block);
+   if (add_normal_successors)
+      block_add_normal_succs(block);
+
+   /* If we've just removed a break, and the block we were jumping to (after
+    * the loop) now has zero predecessors, we've created a new infinite loop.
+    *
+    * NIR doesn't allow blocks (other than the start block) to have zero
+    * predecessors.  In particular, dominance assumes all blocks are reachable.
+    * So, we insert a "fake link" by making successors[1] point after the loop.
+    *
+    * Note that we have to do this after unlinking/recreating the block's
+    * successors.  If we removed a "break" at the end of the loop, then
+    * block == last_block, so block->successors[0] would already be "next",
+    * and adding a fake link would create two identical successors.  Doing
+    * this afterward works, as we'll have changed block->successors[0] to
+    * be the top of the loop.
+    */
+   if (type == nir_jump_break && next->predecessors->entries == 0) {
+      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);
+   }
+}
+
+void
+nir_handle_remove_jump(nir_block *block, nir_jump_type type)
+{
+   unlink_jump(block, type, true);
+
+   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));
+   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, false);
+         } 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);
+
+   /* Dominance and other block-related information is toast. */
+   nir_metadata_preserve(extracted->impl, nir_metadata_none);
+
+   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);
+   }
+}