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/*
* 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.h"
#pragma once
#ifdef __cplusplus
extern "C" {
#endif
/** NIR Control Flow Modification
*
* This file contains various API's that make modifying control flow in NIR,
* while maintaining the invariants checked by the validator, much easier.
* There are two parts to this:
*
* 1. Inserting control flow (if's and loops) in various places, for creating
* IR either from scratch or as part of some lowering pass.
* 2. Taking existing pieces of the IR and either moving them around or
* deleting them.
*/
/** Control flow insertion. */
/** puts a control flow node where the cursor is */
void nir_cf_node_insert(nir_cursor cursor, nir_cf_node *node);
/** puts a control flow node immediately after another control flow node */
static inline void
nir_cf_node_insert_after(nir_cf_node *node, nir_cf_node *after)
{
nir_cf_node_insert(nir_after_cf_node(node), after);
}
/** puts a control flow node immediately before another control flow node */
static inline void
nir_cf_node_insert_before(nir_cf_node *node, nir_cf_node *before)
{
nir_cf_node_insert(nir_before_cf_node(node), before);
}
/** puts a control flow node at the beginning of a list from an if, loop, or function */
static inline void
nir_cf_node_insert_begin(struct exec_list *list, nir_cf_node *node)
{
nir_cf_node_insert(nir_before_cf_list(list), node);
}
/** puts a control flow node at the end of a list from an if, loop, or function */
static inline void
nir_cf_node_insert_end(struct exec_list *list, nir_cf_node *node)
{
nir_cf_node_insert(nir_after_cf_list(list), node);
}
/** Control flow motion.
*
* These functions let you take a part of a control flow list (basically
* equivalent to a series of statement in GLSL) and "extract" it from the IR,
* so that it's a free-floating piece of IR that can be either re-inserted
* somewhere else or deleted entirely. A few notes on using it:
*
* 1. Phi nodes are considered attached to the piece of control flow that
* their sources come from. There are three places where phi nodes can
* occur, which are the three places where a block can have multiple
* predecessors:
*
* 1) After an if statement, if neither branch ends in a jump.
* 2) After a loop, if there are multiple break's.
* 3) At the beginning of a loop.
*
* For #1, the phi node is considered to be part of the if, and for #2 and
* #3 the phi node is considered to be part of the loop. This allows us to
* keep phi's intact, but it means that phi nodes cannot be separated from
* the control flow they come from. For example, extracting an if without
* extracting all the phi nodes after it is not allowed, and neither is
* extracting only some of the phi nodes at the beginning of a block. It
* also means that extracting from the beginning of a basic block actually
* means extracting from the first non-phi instruction, since there's no
* situation where extracting phi nodes without extracting what comes
* before them makes any sense.
*
* 2. Phi node sources are guaranteed to remain valid, meaning that they still
* correspond one-to-one with the predecessors of the basic block they're
* part of. In addition, the original sources will be preserved unless they
* correspond to a break or continue that was deleted. However, no attempt
* is made to ensure that SSA form is maintained. In particular, it is
* *not* guaranteed that definitions of SSA values will dominate all their
* uses after all is said and done. Either the caller must ensure that this
* is the case, or it must insert extra phi nodes to restore SSA.
*
* 3. It is invalid to move a piece of IR with a break/continue outside of the
* loop it references. Doing this will result in invalid
* successors/predecessors and phi node sources.
*
* 4. It is invalid to move a piece of IR from one function implementation to
* another.
*
* 5. Extracting a control flow list will leave lots of dangling references to
* and from other pieces of the IR. It also leaves things in a not 100%
* consistent state. This means that some things (e.g. inserting
* instructions) might not work reliably on the extracted control flow. It
* also means that extracting control flow without re-inserting it or
* deleting it is a Bad Thing (tm).
*/
typedef struct {
struct exec_list list;
nir_function_impl *impl; /* for cleaning up if the list is deleted */
} nir_cf_list;
void nir_cf_extract(nir_cf_list *extracted, nir_cursor begin, nir_cursor end);
void nir_cf_reinsert(nir_cf_list *cf_list, nir_cursor cursor);
void nir_cf_delete(nir_cf_list *cf_list);
static inline void
nir_cf_list_extract(nir_cf_list *extracted, struct exec_list *cf_list)
{
nir_cf_extract(extracted, nir_before_cf_list(cf_list),
nir_after_cf_list(cf_list));
}
/** removes a control flow node, doing any cleanup necessary */
static inline void
nir_cf_node_remove(nir_cf_node *node)
{
nir_cf_list list;
nir_cf_extract(&list, nir_before_cf_node(node), nir_after_cf_node(node));
nir_cf_delete(&list);
}
#ifdef __cplusplus
}
#endif
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