contrib/gcc/loop-unswitch.c

35 /* This pass moves constant conditions out of loops, duplicating the loop
50    where nothing inside the loop alters cond is transformed
75   Duplicating the loop might lead to code growth exponential in number of
76   branches inside loop, so we limit the number of unswitchings performed
77   in a single loop to PARAM_MAX_UNSWITCH_LEVEL.  We only perform the
82 static struct loop *unswitch_loop (struct loops *, struct loop *,
84 static void unswitch_single_loop (struct loops *, struct loop *, rtx, int);
85 static rtx may_unswitch_on (basic_block, struct loop *, rtx *);
138 /* Main entry point.  Perform loop unswitching on all suitable LOOPS.  */
143   struct loop *loop;
150       /* Removed loop?  */
151       loop = loops->parray[i];
152       if (!loop)
155       if (loop->inner)
158       unswitch_single_loop (loops, loop, NULL_RTX, 0);
170    compares loop invariant cc mode register, return the jump in CINSN.  */
173 may_unswitch_on (basic_block bb, struct loop *loop, rtx *cinsn)
186   /* With branches inside loop.  */
187   if (!flow_bb_inside_loop_p (loop, EDGE_SUCC (bb, 0)->dest)
188       || !flow_bb_inside_loop_p (loop, EDGE_SUCC (bb, 1)->dest))
192      are unable to update dominator/irreducible loop information correctly).  */
193   if (!just_once_each_iteration_p (loop, bb))
262 unswitch_single_loop (struct loops *loops, struct loop *loop,
266   struct loop *nloop;
281   if (loop->inner)
284 	fprintf (dump_file, ";; Not unswitching, not innermost loop\n");
288   /* We must be able to duplicate loop body.  */
289   if (!can_duplicate_loop_p (loop))
292 	fprintf (dump_file, ";; Not unswitching, can't duplicate loop\n");
296   /* The loop should not be too large, to limit code growth.  */
297   if (num_loop_insns (loop) > PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
300 	fprintf (dump_file, ";; Not unswitching, loop too big\n");
305   if (!maybe_hot_bb_p (loop->header))
312   /* Nor if the loop usually does not roll.  */
313   if (expected_loop_iterations (loop) < 1)
316 	fprintf (dump_file, ";; Not unswitching, loop iterations < 1\n");
326       bbs = get_loop_body (loop);
327       iv_analysis_loop_init (loop);
328       for (i = 0; i < loop->num_nodes; i++)
329 	if ((cond = may_unswitch_on (bbs[i], loop, &cinsn)))
332       if (i == loop->num_nodes)
376     fprintf (dump_file, ";; Unswitching loop\n");
378   /* Unswitch the loop on this condition.  */
379   nloop = unswitch_loop (loops, loop, bbs[i], cond, cinsn);
384   unswitch_single_loop (loops, loop, conds, num + 1);
396    determining which loop is entered.  Returns NULL if impossible, new loop
397    otherwise.  The new loop is entered if COND is true.  If CINSN is not
400 static struct loop *
401 unswitch_loop (struct loops *loops, struct loop *loop, basic_block unswitch_on,
406   struct loop *nloop;
412   gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on));
414   gcc_assert (just_once_each_iteration_p (loop, unswitch_on));
415   gcc_assert (!loop->inner);
416   gcc_assert (flow_bb_inside_loop_p (loop, EDGE_SUCC (unswitch_on, 0)->dest));
417   gcc_assert (flow_bb_inside_loop_p (loop, EDGE_SUCC (unswitch_on, 1)->dest));
419   entry = loop_preheader_edge (loop);
426   if (!duplicate_loop_to_header_edge (loop, entry, loops, 1,
439   latch_edge = single_succ_edge (get_bb_copy (loop->latch));
468   /* Loopify from the copy of LOOP body, constructing the new loop.  */
470 		   single_pred_edge (get_bb_copy (loop->header)), switch_bb,
477   /* One of created loops do not have to be subloop of the outer loop now,
478      so fix its placement in loop data structure.  */
479   fix_loop_placement (loop);
482   /* Preserve the simple loop preheaders.  */
483   loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);