On Fri, Mar 04, 2022 at 02:58:37PM +0100, Jakub Jelinek via Gcc-patches wrote:
> On Thu, Mar 03, 2022 at 05:08:30PM -0700, Martin Sebor wrote:
> > > 1) shouldn't it give up for EDGE_ABNORMAL too? I mean, e.g.
> > > following a non-local goto forced edge from a noreturn call
> > > to a non-local label (if there is just one) doesn't seem
> > > right to me
> >
> > Possibly yes. I can add it but I don't have a lot of experience with
> > these bits so if you can suggest a test case to exercise this that
> > would be helpful.
>
> Something like:
> void
> foo (void)
> {
> __label__ l;
> __attribute__((noreturn)) void bar (int x) { if (x) goto l; __builtin_trap
> (); }
> bar (0);
> l:;
> }
> shows a single EDGE_ABNORMAL from the bar call.
> But it would need tweaking for the ptr use and clobber.
>
> > > 2) if EDGE_DFS_BACK is computed and 1) is done, is there any
> > > reason why you need 2 levels of protection, i.e. the EDGE_DFS_BACK
> > > check as well as the visited bitmap (and having them use
> > > very different answers, if EDGE_DFS_BACK is seen, the function
> > > will return false, if visited bitmap has a bb, it will return true)?
> > > Can't the visited bitmap go away?
> >
> > Possibly. As I said above, I don't have enough experience with these
> > bits to make (and test) the changes quickly, or enough bandwidth to
> > come up to speed on them. Please feel free to make these improvements.
>
> I'll change that if it passes testing.
Here is a patch to do both. I don't think we really need to have a testcase
for the EDGE_ABNORMAL case (Martin, feel free to add it later), abnormal
edges simply aren't normal control flow and what exactly it means varies.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-03-05 Jakub Jelinek <ja...@redhat.com>
* gimple-ssa-warn-access.cc (pass_waccess::use_after_inval_p): Remove
visited bitmap and its use. Also punt on EDGE_ABNORMAL edges.
--- gcc/gimple-ssa-warn-access.cc.jj 2022-03-03 22:09:22.073800776 +0100
+++ gcc/gimple-ssa-warn-access.cc 2022-03-04 19:21:18.840416075 +0100
@@ -3812,20 +3812,15 @@ pass_waccess::use_after_inval_p (gimple
/* Proceed only when looking for uses of dangling pointers. */
auto gsi = gsi_for_stmt (use_stmt);
- auto_bitmap visited;
-
/* A use statement in the last basic block in a function or one that
falls through to it is after any other prior clobber of the used
variable unless it's followed by a clobber of the same variable. */
basic_block bb = use_bb;
while (bb != inval_bb
&& single_succ_p (bb)
- && !(single_succ_edge (bb)->flags & (EDGE_EH|EDGE_DFS_BACK)))
+ && !(single_succ_edge (bb)->flags
+ & (EDGE_EH | EDGE_ABNORMAL | EDGE_DFS_BACK)))
{
- if (!bitmap_set_bit (visited, bb->index))
- /* Avoid cycles. */
- return true;
-
for (; !gsi_end_p (gsi); gsi_next_nondebug (&gsi))
{
gimple *stmt = gsi_stmt (gsi);
Jakub
