1 /* 2 * Copyright 2014 Intel Corporation 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining a 5 * copy of this software and associated documentation files (the "Software"), 6 * to deal in the Software without restriction, including without limitation 7 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 8 * and/or sell copies of the Software, and to permit persons to whom the 9 * Software is furnished to do so, subject to the following conditions: 10 * 11 * The above copyright notice and this permission notice (including the next 12 * paragraph) shall be included in all copies or substantial portions of the 13 * Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 21 * IN THE SOFTWARE. 22 * 23 * Authors: 24 * Connor Abbott (cwabbott0 (at) gmail.com) 25 * 26 */ 27 28 #include "nir.h" 29 30 #pragma once 31 32 #ifdef __cplusplus 33 extern "C" { 34 #endif 35 36 /** NIR Control Flow Modification 37 * 38 * This file contains various API's that make modifying control flow in NIR, 39 * while maintaining the invariants checked by the validator, much easier. 40 * There are two parts to this: 41 * 42 * 1. Inserting control flow (if's and loops) in various places, for creating 43 * IR either from scratch or as part of some lowering pass. 44 * 2. Taking existing pieces of the IR and either moving them around or 45 * deleting them. 46 */ 47 48 /** Control flow insertion. */ 49 50 /** puts a control flow node where the cursor is */ 51 void nir_cf_node_insert(nir_cursor cursor, nir_cf_node *node); 52 53 /** puts a control flow node immediately after another control flow node */ 54 static inline void 55 nir_cf_node_insert_after(nir_cf_node *node, nir_cf_node *after) 56 { 57 nir_cf_node_insert(nir_after_cf_node(node), after); 58 } 59 60 /** puts a control flow node immediately before another control flow node */ 61 static inline void 62 nir_cf_node_insert_before(nir_cf_node *node, nir_cf_node *before) 63 { 64 nir_cf_node_insert(nir_before_cf_node(node), before); 65 } 66 67 /** puts a control flow node at the beginning of a list from an if, loop, or function */ 68 static inline void 69 nir_cf_node_insert_begin(struct exec_list *list, nir_cf_node *node) 70 { 71 nir_cf_node_insert(nir_before_cf_list(list), node); 72 } 73 74 /** puts a control flow node at the end of a list from an if, loop, or function */ 75 static inline void 76 nir_cf_node_insert_end(struct exec_list *list, nir_cf_node *node) 77 { 78 nir_cf_node_insert(nir_after_cf_list(list), node); 79 } 80 81 82 /** Control flow motion. 83 * 84 * These functions let you take a part of a control flow list (basically 85 * equivalent to a series of statement in GLSL) and "extract" it from the IR, 86 * so that it's a free-floating piece of IR that can be either re-inserted 87 * somewhere else or deleted entirely. A few notes on using it: 88 * 89 * 1. Phi nodes are considered attached to the piece of control flow that 90 * their sources come from. There are three places where phi nodes can 91 * occur, which are the three places where a block can have multiple 92 * predecessors: 93 * 94 * 1) After an if statement, if neither branch ends in a jump. 95 * 2) After a loop, if there are multiple break's. 96 * 3) At the beginning of a loop. 97 * 98 * For #1, the phi node is considered to be part of the if, and for #2 and 99 * #3 the phi node is considered to be part of the loop. This allows us to 100 * keep phi's intact, but it means that phi nodes cannot be separated from 101 * the control flow they come from. For example, extracting an if without 102 * extracting all the phi nodes after it is not allowed, and neither is 103 * extracting only some of the phi nodes at the beginning of a block. It 104 * also means that extracting from the beginning of a basic block actually 105 * means extracting from the first non-phi instruction, since there's no 106 * situation where extracting phi nodes without extracting what comes 107 * before them makes any sense. 108 * 109 * 2. Phi node sources are guaranteed to remain valid, meaning that they still 110 * correspond one-to-one with the predecessors of the basic block they're 111 * part of. In addition, the original sources will be preserved unless they 112 * correspond to a break or continue that was deleted. However, no attempt 113 * is made to ensure that SSA form is maintained. In particular, it is 114 * *not* guaranteed that definitions of SSA values will dominate all their 115 * uses after all is said and done. Either the caller must ensure that this 116 * is the case, or it must insert extra phi nodes to restore SSA. 117 * 118 * 3. It is invalid to move a piece of IR with a break/continue outside of the 119 * loop it references. Doing this will result in invalid 120 * successors/predecessors and phi node sources. 121 * 122 * 4. It is invalid to move a piece of IR from one function implementation to 123 * another. 124 * 125 * 5. Extracting a control flow list will leave lots of dangling references to 126 * and from other pieces of the IR. It also leaves things in a not 100% 127 * consistent state. This means that some things (e.g. inserting 128 * instructions) might not work reliably on the extracted control flow. It 129 * also means that extracting control flow without re-inserting it or 130 * deleting it is a Bad Thing (tm). 131 */ 132 133 typedef struct { 134 struct exec_list list; 135 nir_function_impl *impl; /* for cleaning up if the list is deleted */ 136 } nir_cf_list; 137 138 void nir_cf_extract(nir_cf_list *extracted, nir_cursor begin, nir_cursor end); 139 140 void nir_cf_reinsert(nir_cf_list *cf_list, nir_cursor cursor); 141 142 void nir_cf_delete(nir_cf_list *cf_list); 143 144 void nir_cf_list_clone(nir_cf_list *dst, nir_cf_list *src, nir_cf_node *parent, 145 struct hash_table *remap_table); 146 147 static inline void 148 nir_cf_list_extract(nir_cf_list *extracted, struct exec_list *cf_list) 149 { 150 nir_cf_extract(extracted, nir_before_cf_list(cf_list), 151 nir_after_cf_list(cf_list)); 152 } 153 154 /** removes a control flow node, doing any cleanup necessary */ 155 static inline void 156 nir_cf_node_remove(nir_cf_node *node) 157 { 158 nir_cf_list list; 159 nir_cf_extract(&list, nir_before_cf_node(node), nir_after_cf_node(node)); 160 nir_cf_delete(&list); 161 } 162 163 #ifdef __cplusplus 164 } 165 #endif 166
