gcc/gcc/tree-ssa-loop-ch.c

59    in the loop body are always executed when the loop is entered.  This
61    for loop preconditioning.  */
68 should_duplicate_loop_header_p (basic_block header, struct loop *loop,
75      loop peeling here).  */
83   if (optimize_loop_for_size_p (loop))
89   if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)
90       && flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 1)->dest))
93   /* If this is not the original loop header, we want it to have just
95   if (header != loop->header && !single_pred_p (header))
125 /* Checks whether LOOP is a do-while style loop.  */
128 do_while_loop_p (struct loop *loop)
130   gimple stmt = last_stmt (loop->latch);
132   /* If the latch of the loop is not empty, it is not a do-while loop.  */
137   /* If the header contains just a condition, it is not a do-while loop.  */
138   stmt = last_and_only_stmt (loop->header);
146 /* For all loops, copy the condition at the end of the loop body in front
147    of the loop.  This is beneficial since it increases efficiency of
148    code motion optimizations.  It also saves one jump on entry to the loop.  */
181   struct loop *loop;
201   FOR_EACH_LOOP (loop, 0)
206       header = loop->header;
208       /* If the loop is already a do-while style one (either because it was
210 	 we might be in fact peeling the first iteration of the loop.  This
212       if (do_while_loop_p (loop))
223       while (should_duplicate_loop_header_p (header, loop, &limit))
225 	  /* Find a successor of header that is inside a loop; i.e. the new
227 	  if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest))
241 		 "Duplicating header of the loop %d up to edge %d->%d.\n",
242 		 loop->num, exit->src->index, exit->dest->index);
245 	 inside the loop.  */
249       entry = loop_preheader_edge (loop);
259       /* If the loop has the form "for (i = j; i < j + 10; i++)" then
292 	 are not now, since there was the loop exit condition.  */
293       split_edge (loop_preheader_edge (loop));
294       split_edge (loop_latch_edge (loop));