OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

waccess: Remove visited bitmap and stop on EDGE_ABNORMAL

Browse Source 
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.

2022-03-05  Jakub Jelinek  <jakub@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.
This commit is contained in:
Jakub Jelinek 2022-03-05 12:20:47 +01:00
parent 8ea4a34bd0
commit dab41c9d9f
1 changed files with 2 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gcc/gimple-ssa-warn-access.cc
View File

@ -3812,20 +3812,15 @@ pass_waccess::use_after_inval_p (gimple *inval_stmt, gimple *use_stmt,
/* 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);