static void copy_loop_headers (void) { struct loops *loops; unsigned i; struct loop *loop; basic_block header; edge exit; basic_block *bbs; unsigned n_bbs; loops = loop_optimizer_init (dump_file); if (!loops) return; rewrite_into_loop_closed_ssa (); /* We do not try to keep the information about irreducible regions up-to-date. */ loops->state &= ~LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS; #ifdef ENABLE_CHECKING verify_loop_structure (loops); #endif bbs = xmalloc (sizeof (basic_block) * n_basic_blocks); for (i = 1; i < loops->num; i++) { /* Copy at most 20 insns. */ int limit = 20; loop = loops->parray[i]; if (!loop) continue; header = loop->header; /* If the loop is already a do-while style one (either because it was written as such, or because jump threading transformed it into one), we might be in fact peeling the first iteration of the loop. This in general is not a good idea. */ if (do_while_loop_p (loop)) continue; /* Iterate the header copying up to limit; this takes care of the cases like while (a && b) {...}, where we want to have both of the conditions copied. TODO -- handle while (a || b) - like cases, by not requiring the header to have just a single successor and copying up to postdominator. */ exit = NULL; n_bbs = 0; while (should_duplicate_loop_header_p (header, loop, &limit)) { /* Find a successor of header that is inside a loop; i.e. the new header after the condition is copied. */ if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)) exit = EDGE_SUCC (header, 0); else exit = EDGE_SUCC (header, 1); bbs[n_bbs++] = header; header = exit->dest; } if (!exit) continue; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Duplicating header of the loop %d up to edge %d->%d.\n", loop->num, exit->src->index, exit->dest->index); /* Ensure that the header will have just the latch as a predecessor inside the loop. */ if (EDGE_COUNT (exit->dest->preds) > 1) exit = EDGE_SUCC (loop_split_edge_with (exit, NULL), 0); if (!tree_duplicate_sese_region (loop_preheader_edge (loop), exit, bbs, n_bbs, NULL)) { fprintf (dump_file, "Duplication failed.\n"); continue; } /* Ensure that the latch and the preheader is simple (we know that they are not now, since there was the loop exit condition. */ loop_split_edge_with (loop_preheader_edge (loop), NULL); loop_split_edge_with (loop_latch_edge (loop), NULL); } free (bbs); #ifdef ENABLE_CHECKING verify_loop_closed_ssa (); #endif loop_optimizer_finalize (loops, NULL); }
static unsigned int copy_loop_headers (void) { struct loops *loops; unsigned i; struct loop *loop; basic_block header; edge exit, entry; basic_block *bbs, *copied_bbs; unsigned n_bbs; unsigned bbs_size; loops = loop_optimizer_init (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES); if (!loops) return 0; #ifdef ENABLE_CHECKING verify_loop_structure (loops); #endif bbs = XNEWVEC (basic_block, n_basic_blocks); copied_bbs = XNEWVEC (basic_block, n_basic_blocks); bbs_size = n_basic_blocks; for (i = 1; i < loops->num; i++) { /* Copy at most 20 insns. */ int limit = 20; loop = loops->parray[i]; if (!loop) continue; header = loop->header; /* If the loop is already a do-while style one (either because it was written as such, or because jump threading transformed it into one), we might be in fact peeling the first iteration of the loop. This in general is not a good idea. */ if (do_while_loop_p (loop)) continue; /* Iterate the header copying up to limit; this takes care of the cases like while (a && b) {...}, where we want to have both of the conditions copied. TODO -- handle while (a || b) - like cases, by not requiring the header to have just a single successor and copying up to postdominator. */ exit = NULL; n_bbs = 0; while (should_duplicate_loop_header_p (header, loop, &limit)) { /* Find a successor of header that is inside a loop; i.e. the new header after the condition is copied. */ if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)) exit = EDGE_SUCC (header, 0); else exit = EDGE_SUCC (header, 1); bbs[n_bbs++] = header; gcc_assert (bbs_size > n_bbs); header = exit->dest; } if (!exit) continue; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Duplicating header of the loop %d up to edge %d->%d.\n", loop->num, exit->src->index, exit->dest->index); /* Ensure that the header will have just the latch as a predecessor inside the loop. */ if (!single_pred_p (exit->dest)) exit = single_pred_edge (loop_split_edge_with (exit, NULL)); entry = loop_preheader_edge (loop); if (!tree_duplicate_sese_region (entry, exit, bbs, n_bbs, copied_bbs)) { fprintf (dump_file, "Duplication failed.\n"); continue; } /* If the loop has the form "for (i = j; i < j + 10; i++)" then this copying can introduce a case where we rely on undefined signed overflow to eliminate the preheader condition, because we assume that "j < j + 10" is true. We don't want to warn about that case for -Wstrict-overflow, because in general we don't warn about overflow involving loops. Prevent the warning by setting TREE_NO_WARNING. */ if (warn_strict_overflow > 0) { unsigned int i; for (i = 0; i < n_bbs; ++i) { tree last; last = last_stmt (copied_bbs[i]); if (TREE_CODE (last) == COND_EXPR) TREE_NO_WARNING (last) = 1; } } /* Ensure that the latch and the preheader is simple (we know that they are not now, since there was the loop exit condition. */ loop_split_edge_with (loop_preheader_edge (loop), NULL); loop_split_edge_with (loop_latch_edge (loop), NULL); } free (bbs); free (copied_bbs); loop_optimizer_finalize (loops); return 0; }