diff options
Diffstat (limited to 'gcc/tree-ssa-threadupdate.c')
| -rw-r--r-- | gcc/tree-ssa-threadupdate.c | 34 |
1 files changed, 26 insertions, 8 deletions
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c index 3d3aeab..045905e 100644 --- a/gcc/tree-ssa-threadupdate.c +++ b/gcc/tree-ssa-threadupdate.c @@ -2174,7 +2174,6 @@ thread_through_all_blocks (bool may_peel_loop_headers) { bool retval = false; unsigned int i; - bitmap_iterator bi; struct loop *loop; auto_bitmap threaded_blocks; @@ -2278,14 +2277,33 @@ thread_through_all_blocks (bool may_peel_loop_headers) initialize_original_copy_tables (); - /* First perform the threading requests that do not affect - loop structure. */ - EXECUTE_IF_SET_IN_BITMAP (threaded_blocks, 0, i, bi) - { - basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i); + /* The order in which we process jump threads can be important. + + Consider if we have two jump threading paths A and B. If the + target edge of A is the starting edge of B and we thread path A + first, then we create an additional incoming edge into B->dest that + we can not discover as a jump threading path on this iteration. + + If we instead thread B first, then the edge into B->dest will have + already been redirected before we process path A and path A will + natually, with no further work, target the redirected path for B. - if (EDGE_COUNT (bb->preds) > 0) - retval |= thread_block (bb, true); + An post-order is sufficient here. Compute the ordering first, then + process the blocks. */ + if (!bitmap_empty_p (threaded_blocks)) + { + int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun)); + unsigned int postorder_num = post_order_compute (postorder, false, false); + for (unsigned int i = 0; i < postorder_num; i++) + { + unsigned int indx = postorder[i]; + if (bitmap_bit_p (threaded_blocks, indx)) + { + basic_block bb = BASIC_BLOCK_FOR_FN (cfun, indx); + retval |= thread_block (bb, true); + } + } + free (postorder); } /* Then perform the threading through loop headers. We start with the |