diff options
Diffstat (limited to 'gcc/tree-ssa-threadupdate.c')
| -rw-r--r-- | gcc/tree-ssa-threadupdate.c | 124 |
1 files changed, 57 insertions, 67 deletions
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c index 1a52e4702fa..c0476b48a1c 100644 --- a/gcc/tree-ssa-threadupdate.c +++ b/gcc/tree-ssa-threadupdate.c @@ -1,5 +1,5 @@ /* Thread edges through blocks and update the control flow and SSA graphs. - Copyright (C) 2004-2013 Free Software Foundation, Inc. + Copyright (C) 2004-2014 Free Software Foundation, Inc. This file is part of GCC. @@ -421,27 +421,22 @@ create_edge_and_update_destination_phis (struct redirection_data *rd, e->probability = REG_BR_PROB_BASE; e->count = bb->count; - /* We have to copy path -- which means creating a new vector as well - as all the jump_thread_edge entries. */ - if (rd->path->last ()->e->aux) - { - vec<jump_thread_edge *> *path = THREAD_PATH (rd->path->last ()->e); - vec<jump_thread_edge *> *copy = new vec<jump_thread_edge *> (); + /* We used to copy the thread path here. That was added in 2007 + and dutifully updated through the representation changes in 2013. - /* Sadly, the elements of the vector are pointers and need to - be copied as well. */ - for (unsigned int i = 0; i < path->length (); i++) - { - jump_thread_edge *x - = new jump_thread_edge ((*path)[i]->e, (*path)[i]->type); - copy->safe_push (x); - } - e->aux = (void *)copy; - } - else - { - e->aux = NULL; - } + In 2013 we added code to thread from an interior node through + the backedge to another interior node. That runs after the code + to thread through loop headers from outside the loop. + + The latter may delete edges in the CFG, including those + which appeared in the jump threading path we copied here. Thus + we'd end up using a dangling pointer. + + After reviewing the 2007/2011 code, I can't see how anything + depended on copying the AUX field and clearly copying the jump + threading path is problematical due to embedded edge pointers. + It has been removed. */ + e->aux = NULL; /* If there are any PHI nodes at the destination of the outgoing edge from the duplicate block, then we will need to add a new argument @@ -1417,7 +1412,7 @@ mark_threaded_blocks (bitmap threaded_blocks) { EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi) { - bb = BASIC_BLOCK (i); + bb = BASIC_BLOCK_FOR_FN (cfun, i); if (EDGE_COUNT (bb->preds) > 1 && !redirection_block_p (bb)) { @@ -1447,51 +1442,39 @@ mark_threaded_blocks (bitmap threaded_blocks) by trimming off the end of the jump thread path. */ EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi) { - basic_block bb = BASIC_BLOCK (i); + basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i); FOR_EACH_EDGE (e, ei, bb->preds) { if (e->aux) { vec<jump_thread_edge *> *path = THREAD_PATH (e); - /* Basically we're looking for a situation where we can see - 3 or more loop structures on a jump threading path. */ - - struct loop *first_father = (*path)[0]->e->src->loop_father; - struct loop *second_father = NULL; - for (unsigned int i = 0; i < path->length (); i++) + for (unsigned int i = 0, crossed_headers = 0; + i < path->length (); + i++) { - /* See if this is a loop father we have not seen before. */ - if ((*path)[i]->e->dest->loop_father != first_father - && (*path)[i]->e->dest->loop_father != second_father) + basic_block dest = (*path)[i]->e->dest; + crossed_headers += (dest == dest->loop_father->header); + if (crossed_headers > 1) { - /* We've already seen two loop fathers, so we - need to trim this jump threading path. */ - if (second_father != NULL) + /* Trim from entry I onwards. */ + for (unsigned int j = i; j < path->length (); j++) + delete (*path)[j]; + path->truncate (i); + + /* Now that we've truncated the path, make sure + what's left is still valid. We need at least + two edges on the path and the last edge can not + be a joiner. This should never happen, but let's + be safe. */ + if (path->length () < 2 + || (path->last ()->type + == EDGE_COPY_SRC_JOINER_BLOCK)) { - /* Trim from entry I onwards. */ - for (unsigned int j = i; j < path->length (); j++) - delete (*path)[j]; - path->truncate (i); - - /* Now that we've truncated the path, make sure - what's left is still valid. We need at least - two edges on the path and the last edge can not - be a joiner. This should never happen, but let's - be safe. */ - if (path->length () < 2 - || (path->last ()->type - == EDGE_COPY_SRC_JOINER_BLOCK)) - { - delete_jump_thread_path (path); - e->aux = NULL; - } - break; - } - else - { - second_father = (*path)[i]->e->dest->loop_father; + delete_jump_thread_path (path); + e->aux = NULL; } + break; } } } @@ -1517,7 +1500,7 @@ mark_threaded_blocks (bitmap threaded_blocks) we have to iterate on those rather than the threaded_edges vector. */ EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi) { - bb = BASIC_BLOCK (i); + bb = BASIC_BLOCK_FOR_FN (cfun, i); FOR_EACH_EDGE (e, ei, bb->preds) { if (e->aux) @@ -1597,7 +1580,7 @@ thread_through_all_blocks (bool may_peel_loop_headers) loop structure. */ EXECUTE_IF_SET_IN_BITMAP (threaded_blocks, 0, i, bi) { - basic_block bb = BASIC_BLOCK (i); + basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i); if (EDGE_COUNT (bb->preds) > 0) retval |= thread_block (bb, true); @@ -1636,7 +1619,7 @@ thread_through_all_blocks (bool may_peel_loop_headers) ahead and thread it, else ignore it. */ basic_block bb; edge e; - FOR_EACH_BB (bb) + FOR_EACH_BB_FN (bb, cfun) { /* If we do end up threading here, we can remove elements from BB->preds. Thus we can not use the FOR_EACH_EDGE iterator. */ @@ -1676,13 +1659,20 @@ thread_through_all_blocks (bool may_peel_loop_headers) { struct loop *loop = (*path)[0]->e->dest->loop_father; - retval |= thread_block ((*path)[0]->e->dest, false); - e->aux = NULL; - - /* This jump thread likely totally scrambled this loop. - So arrange for it to be fixed up. */ - loop->header = NULL; - loop->latch = NULL; + if (thread_block ((*path)[0]->e->dest, false)) + { + /* This jump thread likely totally scrambled this loop. + So arrange for it to be fixed up. */ + loop->header = NULL; + loop->latch = NULL; + e->aux = NULL; + } + else + { + delete_jump_thread_path (path); + e->aux = NULL; + ei_next (&ei); + } } } else |