2 * dominators.c: Dominator computation on the control flow graph
5 * Dietmar Maurer (dietmar@ximian.com)
6 * Paolo Molaro (lupus@ximian.com)
8 * (C) 2003 Ximian, Inc.
9 * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
12 #include <mono/metadata/debug-helpers.h>
13 #include <mono/metadata/mempool.h>
14 #include <mono/metadata/mempool-internals.h>
21 * bb->dfn == 0 means either the bblock is ignored by the dfn calculation, or
22 * it is the entry bblock.
24 #define HAS_DFN(bb, entry) ((bb)->dfn || ((bb) == entry))
27 * Compute dominators and immediate dominators using the algorithm in the
28 * paper "A Simple, Fast Dominance Algorithm" by Keith D. Cooper,
29 * Timothy J. Harvey, and Ken Kennedy:
30 * http://citeseer.ist.psu.edu/cooper01simple.html
33 compute_dominators (MonoCompile
*cfg
)
35 int bindex
, i
, bitsize
;
36 MonoBasicBlock
*entry
;
37 MonoBasicBlock
**doms
;
40 g_assert (!(cfg
->comp_done
& MONO_COMP_DOM
));
42 bitsize
= mono_bitset_alloc_size (cfg
->num_bblocks
, 0);
44 entry
= cfg
->bblocks
[0];
46 doms
= g_new0 (MonoBasicBlock
*, cfg
->num_bblocks
);
47 doms
[entry
->dfn
] = entry
;
49 if (cfg
->verbose_level
> 1) {
50 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
52 MonoBasicBlock
*bb
= cfg
->bblocks
[i
];
54 printf ("BB%d IN: ", bb
->block_num
);
55 for (j
= 0; j
< bb
->in_count
; ++j
)
56 printf ("%d ", bb
->in_bb
[j
]->block_num
);
65 for (bindex
= 0; bindex
< cfg
->num_bblocks
; ++bindex
) {
66 MonoBasicBlock
*bb
= cfg
->bblocks
[bindex
];
70 for (i
= 0; i
< bb
->in_count
; ++i
) {
71 MonoBasicBlock
*in_bb
= bb
->in_bb
[i
];
72 if ((in_bb
!= bb
) && doms
[in_bb
->dfn
]) {
77 if (bb
!= cfg
->bblocks
[0])
80 while (i
< bb
->in_count
) {
81 MonoBasicBlock
*in_bb
= bb
->in_bb
[i
];
83 if (HAS_DFN (in_bb
, entry
) && doms
[in_bb
->dfn
]) {
85 MonoBasicBlock
*f1
= idom
;
86 MonoBasicBlock
*f2
= in_bb
;
89 if (f1
->dfn
< f2
->dfn
)
100 if (idom
!= doms
[bb
->dfn
]) {
101 if (bb
== cfg
->bblocks
[0])
104 doms
[bb
->dfn
] = idom
;
108 //printf ("A: bb=%d dfn=%d dom:%d\n", bb->block_num, bb->dfn, doms [bb->dfn]->block_num);
113 /* Compute bb->dominators for each bblock */
114 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
115 MonoBasicBlock
*bb
= cfg
->bblocks
[i
];
117 MonoBitSet
*dominators
;
120 mem
= mono_mempool_alloc0 (cfg
->mempool
, bitsize
);
122 bb
->dominators
= dominators
= mono_bitset_mem_new (mem
, cfg
->num_bblocks
, 0);
125 mono_bitset_set_fast (dominators
, bb
->dfn
);
128 for (cbb
= doms
[bb
->dfn
]; cbb
->dfn
; cbb
= doms
[cbb
->dfn
])
129 mono_bitset_set_fast (dominators
, cbb
->dfn
);
131 bb
->idom
= doms
[bb
->dfn
];
133 bb
->idom
->dominated
= g_slist_prepend_mempool (cfg
->mempool
, bb
->idom
->dominated
, bb
);
137 mono_bitset_set_fast (dominators
, 0);
142 cfg
->comp_done
|= MONO_COMP_DOM
| MONO_COMP_IDOM
;
144 if (cfg
->verbose_level
> 1) {
145 printf ("DTREE %s %d\n", mono_method_full_name (cfg
->method
, TRUE
),
146 cfg
->header
->num_clauses
);
147 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
148 MonoBasicBlock
*bb
= cfg
->bblocks
[i
];
149 printf ("BB%d(dfn=%d) (IDOM=BB%d): ", bb
->block_num
, bb
->dfn
, bb
->idom
? bb
->idom
->block_num
: -1);
150 mono_blockset_print (cfg
, bb
->dominators
, NULL
, -1);
158 check_dominance_frontier (MonoBasicBlock
*x
, MonoBasicBlock
*t
)
162 t
->flags
|= BB_VISITED
;
164 if (mono_bitset_test_fast (t
->dominators
, x
->dfn
)) {
165 for (i
= 0; i
< t
->out_count
; ++i
) {
166 if (!(t
->flags
& BB_VISITED
)) {
168 check_dominance_frontier (x
, t
->out_bb
[i
]);
170 for (j
= 0; j
< t
->out_bb
[i
]->in_count
; j
++) {
171 if (t
->out_bb
[i
]->in_bb
[j
] == t
)
178 if (!mono_bitset_test_fast (x
->dfrontier
, t
->dfn
)) {
179 printf ("BB%d not in frontier of BB%d\n", t
->block_num
, x
->block_num
);
180 g_assert_not_reached ();
188 * Compute dominance frontiers using the algorithm from the same paper.
191 compute_dominance_frontier (MonoCompile
*cfg
)
196 g_assert (!(cfg
->comp_done
& MONO_COMP_DFRONTIER
));
198 for (i
= 0; i
< cfg
->num_bblocks
; ++i
)
199 cfg
->bblocks
[i
]->flags
&= ~BB_VISITED
;
201 bitsize
= mono_bitset_alloc_size (cfg
->num_bblocks
, 0);
202 mem
= mono_mempool_alloc0 (cfg
->mempool
, bitsize
* cfg
->num_bblocks
);
204 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
205 MonoBasicBlock
*bb
= cfg
->bblocks
[i
];
206 bb
->dfrontier
= mono_bitset_mem_new (mem
, cfg
->num_bblocks
, 0);
210 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
211 MonoBasicBlock
*bb
= cfg
->bblocks
[i
];
213 if (bb
->in_count
> 1) {
214 for (j
= 0; j
< bb
->in_count
; ++j
) {
215 MonoBasicBlock
*p
= bb
->in_bb
[j
];
217 if (p
->dfn
|| (p
== cfg
->bblocks
[0])) {
218 while (p
!= bb
->idom
) {
219 mono_bitset_set_fast (p
->dfrontier
, bb
->dfn
);
228 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
229 MonoBasicBlock
*bb
= cfg
->bblocks
[i
];
231 printf ("DFRONT %s BB%d: ", mono_method_full_name (cfg
->method
, TRUE
), bb
->block_num
);
232 mono_blockset_print (cfg
, bb
->dfrontier
, NULL
, -1);
237 /* this is a check for the dominator frontier */
238 for (i
= 0; i
< m
->num_bblocks
; ++i
) {
239 MonoBasicBlock
*x
= m
->bblocks
[i
];
241 mono_bitset_foreach_bit ((x
->dfrontier
), j
, (m
->num_bblocks
)) {
242 MonoBasicBlock
*w
= m
->bblocks
[j
];
244 /* x must not strictly dominates w */
245 if (mono_bitset_test_fast (w
->dominators
, x
->dfn
) && w
!= x
)
246 g_assert_not_reached ();
248 for (k
= 0; k
< m
->num_bblocks
; ++k
)
249 m
->bblocks
[k
]->flags
&= ~BB_VISITED
;
251 check_dominance_frontier (x
, x
);
256 cfg
->comp_done
|= MONO_COMP_DFRONTIER
;
260 df_set (MonoCompile
*m
, MonoBitSet
* dest
, MonoBitSet
*set
)
264 mono_bitset_foreach_bit (set
, i
, m
->num_bblocks
) {
265 mono_bitset_union_fast (dest
, m
->bblocks
[i
]->dfrontier
);
270 mono_compile_iterated_dfrontier (MonoCompile
*m
, MonoBitSet
*set
)
273 int bitsize
, count1
, count2
;
275 bitsize
= mono_bitset_alloc_size (m
->num_bblocks
, 0);
276 result
= mono_bitset_mem_new (mono_mempool_alloc0 (m
->mempool
, bitsize
), m
->num_bblocks
, 0);
278 df_set (m
, result
, set
);
279 count2
= mono_bitset_count (result
);
282 df_set (m
, result
, result
);
283 count2
= mono_bitset_count (result
);
284 } while (count2
> count1
);
290 mono_compile_dominator_info (MonoCompile
*cfg
, int dom_flags
)
292 if ((dom_flags
& MONO_COMP_DOM
) && !(cfg
->comp_done
& MONO_COMP_DOM
))
293 compute_dominators (cfg
);
294 if ((dom_flags
& MONO_COMP_DFRONTIER
) && !(cfg
->comp_done
& MONO_COMP_DFRONTIER
))
295 compute_dominance_frontier (cfg
);
299 * code to detect loops and loop nesting level
302 mono_compute_natural_loops (MonoCompile
*cfg
)
305 MonoBitSet
*in_loop_blocks
;
308 g_assert (!(cfg
->comp_done
& MONO_COMP_LOOPS
));
310 in_loop_blocks
= mono_bitset_new (cfg
->num_bblocks
+ 1, 0);
311 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
312 MonoBasicBlock
*n
= cfg
->bblocks
[i
];
314 for (j
= 0; j
< n
->out_count
; j
++) {
315 MonoBasicBlock
*h
= n
->out_bb
[j
];
316 /* check for single block loops */
318 h
->loop_blocks
= g_list_prepend_mempool (cfg
->mempool
, h
->loop_blocks
, h
);
321 /* check for back-edge from n to h */
322 else if (n
!= h
&& mono_bitset_test_fast (n
->dominators
, h
->dfn
)) {
325 /* already in loop_blocks? */
326 if (h
->loop_blocks
&& g_list_find (h
->loop_blocks
, n
)) {
330 mono_bitset_clear_all (in_loop_blocks
);
331 if (h
->loop_blocks
) {
334 for (l
= h
->loop_blocks
; l
; l
= l
->next
) {
335 MonoBasicBlock
*b
= l
->data
;
337 mono_bitset_set_fast (in_loop_blocks
, b
->dfn
);
340 todo
= g_slist_prepend (NULL
, n
);
343 MonoBasicBlock
*cb
= (MonoBasicBlock
*)todo
->data
;
344 todo
= g_slist_delete_link (todo
, todo
);
346 if ((cb
->dfn
&& mono_bitset_test_fast (in_loop_blocks
, cb
->dfn
)) || (!cb
->dfn
&& g_list_find (h
->loop_blocks
, cb
)))
349 h
->loop_blocks
= g_list_prepend_mempool (cfg
->mempool
, h
->loop_blocks
, cb
);
352 mono_bitset_set_fast (in_loop_blocks
, cb
->dfn
);
354 for (k
= 0; k
< cb
->in_count
; k
++) {
355 MonoBasicBlock
*prev
= cb
->in_bb
[k
];
356 /* add all previous blocks */
357 if (prev
!= h
&& !((prev
->dfn
&& mono_bitset_test_fast (in_loop_blocks
, prev
->dfn
)) || (!prev
->dfn
&& g_list_find (h
->loop_blocks
, prev
)))) {
358 todo
= g_slist_prepend (todo
, prev
);
363 /* add the header if not already there */
364 if (!((h
->dfn
&& mono_bitset_test_fast (in_loop_blocks
, h
->dfn
)) || (!h
->dfn
&& g_list_find (h
->loop_blocks
, h
)))) {
365 h
->loop_blocks
= g_list_prepend_mempool (cfg
->mempool
, h
->loop_blocks
, h
);
371 mono_bitset_free (in_loop_blocks
);
373 cfg
->comp_done
|= MONO_COMP_LOOPS
;
375 /* Compute loop_body_start for each loop */
376 bb_indexes
= g_new0 (int, cfg
->num_bblocks
);
380 for (i
= 0, bb
= cfg
->bb_entry
; bb
; i
++, bb
= bb
->next_bb
) {
382 bb_indexes
[bb
->dfn
] = i
;
385 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
386 if (cfg
->bblocks
[i
]->loop_blocks
) {
387 /* The loop body start is the first bblock in the order they will be emitted */
388 MonoBasicBlock
*h
= cfg
->bblocks
[i
];
389 MonoBasicBlock
*body_start
= h
;
392 for (l
= h
->loop_blocks
; l
; l
= l
->next
) {
393 MonoBasicBlock
*cb
= (MonoBasicBlock
*)l
->data
;
395 if (cb
->dfn
&& bb_indexes
[cb
->dfn
] < bb_indexes
[body_start
->dfn
]) {
400 body_start
->loop_body_start
= 1;
405 if (cfg
->verbose_level
> 1) {
406 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
407 if (cfg
->bblocks
[i
]->loop_blocks
) {
408 MonoBasicBlock
*h
= (MonoBasicBlock
*)cfg
->bblocks
[i
]->loop_blocks
->data
;
410 printf ("LOOP START %d\n", h
->block_num
);
411 for (l
= h
->loop_blocks
; l
; l
= l
->next
) {
412 MonoBasicBlock
*cb
= (MonoBasicBlock
*)l
->data
;
413 printf ("\tBB%d %d %p\n", cb
->block_num
, cb
->nesting
, cb
->loop_blocks
);
421 clear_idominators (MonoCompile
*cfg
)
425 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
426 if (cfg
->bblocks
[i
]->dominated
) {
427 cfg
->bblocks
[i
]->dominated
= NULL
;
431 cfg
->comp_done
&= ~MONO_COMP_IDOM
;
435 clear_loops (MonoCompile
*cfg
)
439 for (i
= 0; i
< cfg
->num_bblocks
; ++i
) {
440 cfg
->bblocks
[i
]->nesting
= 0;
441 cfg
->bblocks
[i
]->loop_blocks
= NULL
;
444 cfg
->comp_done
&= ~MONO_COMP_LOOPS
;
448 mono_free_loop_info (MonoCompile
*cfg
)
450 if (cfg
->comp_done
& MONO_COMP_IDOM
)
451 clear_idominators (cfg
);
452 if (cfg
->comp_done
& MONO_COMP_LOOPS
)
456 #else /* DISABLE_JIT */
459 mono_free_loop_info (MonoCompile
*cfg
)
463 #endif /* DISABLE_JIT */