1 /*-------------------------------------------------------------------------
3 SDCCcflow.c - source file for control flow analysis
5 Written By - Sandeep Dutta . sandeep.dutta@usa.net (1998)
7 This program is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 2, or (at your option) any
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
21 In other words, you are welcome to use, share and improve this program.
22 You are forbidden to forbid anyone else to use, share and improve
23 what you give them. Help stamp out software-hoarding!
24 -------------------------------------------------------------------------*/
28 /*-----------------------------------------------------------------*/
29 /* domSetFromVect - creates a domset from the vector */
30 /*-----------------------------------------------------------------*/
32 domSetFromVect (eBBlock ** ebbs, bitVect * domVect)
40 for (i = 0; i < domVect->size; i++)
41 if (bitVectBitValue (domVect, i))
42 addSet (&domSet, ebbs[i]);
47 /*-----------------------------------------------------------------*/
48 /* addSuccessor - will add bb to succ also add it to the pred of */
50 /*-----------------------------------------------------------------*/
52 addSuccessor (eBBlock * thisBlock, eBBlock * succ)
54 /* check for boundary conditions */
55 if (!thisBlock || !succ)
58 /* add it to the succ of thisBlock */
59 addSetIfnotP (&thisBlock->succList, succ);
62 bitVectSetBit (thisBlock->succVect, succ->bbnum);
63 /* add this edge to the list of edges */
64 addSet (&graphEdges, newEdge (thisBlock, succ));
68 /*-----------------------------------------------------------------*/
69 /* eBBPredecessors - find the predecessors for each block */
70 /*-----------------------------------------------------------------*/
72 eBBPredecessors (eBBlock ** ebbs, int count)
76 /* for each block do */
77 for (i = 0; i < count; i++)
80 /* if there is no path to this then continue */
84 /* for each successor of this block if */
85 /* it has depth first number > this block */
86 /* then this block precedes the successor */
87 for (j = 0; j < ebbs[i]->succVect->size; j++)
89 if (bitVectBitValue (ebbs[i]->succVect, j) &&
90 ebbs[j]->dfnum > ebbs[i]->dfnum)
92 addSet (&ebbs[j]->predList, ebbs[i]);
96 /*-----------------------------------------------------------------*/
97 /* eBBSuccessors- find out the successors of all the nodes */
98 /*-----------------------------------------------------------------*/
100 eBBSuccessors (eBBlock ** ebbs, int count)
104 /* for all the blocks do */
105 for (; i < count; i++)
112 ebbs[i]->succVect = newBitVect (count);
114 /* if the next on exists & this one does not */
115 /* end in a GOTO or RETURN then the next is */
116 /* a natural successor of this. Note we have */
117 /* consider eBBlocks with no instructions */
124 if (ebbs[i]->ech->op != GOTO &&
125 ebbs[i]->ech->op != RETURN &&
126 ebbs[i]->ech->op != JUMPTABLE)
130 while (ebbs[j] && ebbs[j]->noPath)
133 addSuccessor (ebbs[i], ebbs[j]); /* add it */
135 } /* no instructions in the block */
136 /* could happen for dummy blocks */
138 addSuccessor (ebbs[i], ebbs[i + 1]);
141 /* go thru all the instructions: if we find a */
142 /* goto or ifx or a return then we have a succ */
143 if ((ic = ebbs[i]->ech))
147 /* special case for jumptable */
148 if (ic->op == JUMPTABLE)
151 for (lbl = setFirstItem (IC_JTLABELS (ic)); lbl;
152 lbl = setNextItem (IC_JTLABELS (ic)))
153 addSuccessor (ebbs[i],
154 eBBWithEntryLabel (ebbs, lbl, count));
160 /* depending on the instruction operator */
163 case GOTO: /* goto has edge to label */
164 succ = eBBWithEntryLabel (ebbs, ic->argLabel.label, count);
167 case IFX: /* conditional jump */
168 /* if true label is present */
170 succ = eBBWithEntryLabel (ebbs, IC_TRUE (ic), count);
172 succ = eBBWithEntryLabel (ebbs, IC_FALSE (ic), count);
175 case RETURN: /* block with return */
176 succ = eBBWithEntryLabel (ebbs, returnLabel, count);
180 /* if there is a successor add to the list */
181 /* if it is not already present in the list */
183 addSuccessor (ebbs[i], succ);
189 /*-----------------------------------------------------------------*/
190 /* computeDominance - computes the dominance graph */
191 /* for algorithm look at Dragon book section 10.10, algo 10.16 */
192 /*-----------------------------------------------------------------*/
194 computeDominance (eBBlock ** ebbs, int count)
198 /* now do the initialisation */
199 /* D(n0) := { n0 } */
201 bitVectSetBit (ebbs[0]->domVect = newBitVect (count), ebbs[0]->bbnum);
204 /* for n in N - { n0 } do D(n) = N */
205 for (i = 1; i < count; i++)
207 ebbs[i]->domVect = newBitVect (count);
208 for (j = 0; j < count; j++)
211 bitVectSetBit (ebbs[i]->domVect, ebbs[j]->bbnum);
215 /* end of initialisation */
217 /* while changes to any D(n) occur do */
218 /* for n in N - { n0 } do */
219 /* D(n) := { n } U (intersection of D( all predecessors of n)) */
225 for (i = 1; i < count; i++)
232 /* get the intersection of the dominance of all predecessors */
233 for (pred = setFirstItem (ebbs[i]->predList),
234 cDomVect = (pred ? bitVectCopy (pred->domVect) : NULL);
236 pred = setNextItem (ebbs[i]->predList))
238 cDomVect = bitVectIntersect (cDomVect, pred->domVect);
241 cDomVect = newBitVect (count);
242 /* this node to the list */
243 cDomVect = bitVectSetBit (cDomVect, ebbs[i]->bbnum);
246 if (!bitVectEqual (cDomVect, ebbs[i]->domVect))
248 ebbs[i]->domVect = cDomVect;
253 /* if no change then exit */
259 /*-----------------------------------------------------------------*/
260 /* immedDom - returns the immediate dominator of a block */
261 /*-----------------------------------------------------------------*/
263 immedDom (eBBlock ** ebbs, eBBlock * ebp)
265 /* first delete self from the list */
266 set *iset = domSetFromVect (ebbs, ebp->domVect);
268 eBBlock *idom = NULL;
270 deleteSetItem (&iset, ebp);
271 /* then just return the one with the greatest */
272 /* depthfirst number, this will be the immed dominator */
273 if ((loop = setFirstItem (iset)))
275 for (; loop; loop = setNextItem (iset))
276 if (loop->dfnum > idom->dfnum)
279 setToNull ((void **) &iset);
284 /*-----------------------------------------------------------------*/
285 /* DFOrdering - is visited then nothing else call DFOrdering this */
286 /*-----------------------------------------------------------------*/
287 DEFSETFUNC (DFOrdering)
289 eBBlock *ebbp = item;
290 V_ARG (int *, count);
295 computeDFOrdering (ebbp, count); /* depthfirst */
300 /*-----------------------------------------------------------------*/
301 /* computeDFOrdering - computes the depth first ordering of the */
303 /*-----------------------------------------------------------------*/
305 computeDFOrdering (eBBlock * ebbp, int *count)
309 /* for each successor that is not visited */
310 applyToSet (ebbp->succList, DFOrdering, count);
312 /* set the depth first number */
313 ebbp->dfnum = *count;
317 /*-----------------------------------------------------------------*/
318 /* disconBBlock - removes all control flow links for a block */
319 /*-----------------------------------------------------------------*/
321 disconBBlock (eBBlock * ebp, eBBlock ** ebbs, int count)
323 /* mark this block as noPath & recompute control flow */
325 computeControlFlow (ebbs, count, TRUE);
328 /*-----------------------------------------------------------------*/
329 /* markNoPath - marks those blocks which cannot be reached from top */
330 /*-----------------------------------------------------------------*/
332 markNoPath (eBBlock ** ebbs, int count)
337 /* for all blocks if the visited flag is not set : then there */
338 /* is no path from _entry to this block push them down in the */
339 /* depth first order */
340 for (i = 0; i < count; i++)
341 if (!ebbs[i]->visited)
344 /*-----------------------------------------------------------------*/
345 /* dfNumCompare - used by qsort to sort by dfNumber */
346 /*-----------------------------------------------------------------*/
348 dfNumCompare (const void *a, const void *b)
350 const eBBlock *const *i = a;
351 const eBBlock *const *j = b;
353 if ((*i)->dfnum > (*j)->dfnum)
356 if ((*i)->dfnum < (*j)->dfnum)
362 /*-----------------------------------------------------------------*/
363 /* bbNumCompare - used by qsort to sort by bbNumber */
364 /*-----------------------------------------------------------------*/
366 bbNumCompare (const void *a, const void *b)
368 const eBBlock *const *i = a;
369 const eBBlock *const *j = b;
371 if ((*i)->bbnum > (*j)->bbnum)
374 if ((*i)->bbnum < (*j)->bbnum)
381 /*-----------------------------------------------------------------*/
382 /* computeControlFlow - does the control flow computation */
383 /*-----------------------------------------------------------------*/
385 computeControlFlow (eBBlock ** ebbs, int count, int reSort)
387 int saveCount = count;
390 /* initialise some things */
392 for (i = 0; i < count; i++)
394 setToNull ((void **) &ebbs[i]->predList);
395 setToNull ((void **) &ebbs[i]->domVect);
396 setToNull ((void **) &ebbs[i]->succList);
397 setToNull ((void **) &ebbs[i]->succVect);
398 ebbs[i]->visited = 0;
403 /* sort it back by block number */
404 qsort (ebbs, saveCount, sizeof (eBBlock *), bbNumCompare);
406 setToNull ((void **) &graphEdges);
407 /* this will put in the */
408 /* successor information for each blk */
409 eBBSuccessors (ebbs, count);
411 /* compute the depth first ordering */
412 computeDFOrdering (ebbs[0], &count);
414 /* mark blocks with no paths to them */
415 markNoPath (ebbs, saveCount);
417 /* with the depth first info in place */
418 /* add the predecessors for the blocks */
419 eBBPredecessors (ebbs, saveCount);
421 /* compute the dominance graph */
422 computeDominance (ebbs, saveCount);
424 /* sort it by dfnumber */
425 qsort (ebbs, saveCount, sizeof (eBBlock *), dfNumCompare);