| Message ID | 20200802111720.3410840-1-slyfox@gentoo.org |
|---|---|
| State | New |
| Headers | show |
| Series | var-tracking: fix uninitialised use of 'in_pending' [PR96404] | expand |
On August 2, 2020 1:17:20 PM GMT+02:00, Sergei Trofimovich <slyfox@gentoo.org> wrote: >From: Sergei Trofimovich <siarheit@google.com> > >r11-2447-g:1212cfad093 ("Improve var-tracking dataflow >iteration order") changed 'in_pending' initialization >from: > > in_pending = sbitmap_alloc (last_basic_block_for_fn (cfun)); > bitmap_ones (in_pending); > >to more complex partial bit population algorithm. Due to presence >of uninitialized bits gcc started injecting extra debug entries >in seemigly arbitrary locations and started failing stage2/stage3 >bootstrap comparison. > >valgrind detected unilitialized bits as: > > Conditional jump or move depends on uninitialised value(s) > at 0xDBED3B: vt_find_locations() (var-tracking.c:7230) > by 0xDBF2FB: variable_tracking_main_1() (var-tracking.c:10519) > ... > Uninitialised value was created by a heap allocation > at 0x483779F: malloc (vg_replace_malloc.c:307) > by 0x14EE80B: xmalloc (xmalloc.c:147) > by 0x14911F9: sbitmap_alloc(unsigned int) (sbitmap.c:51) > ... > >The fix explicitly initializes 'in_pending' bitmap with zeros. OK and thanks for tracking this down. Guess the default bootstrap-debug hid this issue for me. Richard. >gcc: > >2020-08-02 Sergei Trofimovich <siarheit@google.com> > > PR bootstrap96404 > * var-tracking.c (vt_find_locations): Fully initialize > all 'in_pending' bits. > >Signed-off-by: Sergei Trofimovich <siarheit@google.com> >--- > gcc/var-tracking.c | 1 + > 1 file changed, 1 insertion(+) > >diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c >index 743f5dcecf6..52aea47a053 100644 >--- a/gcc/var-tracking.c >+++ b/gcc/var-tracking.c >@@ -7096,6 +7096,7 @@ vt_find_locations (void) > in_worklist = sbitmap_alloc (last_basic_block_for_fn (cfun)); > in_pending = sbitmap_alloc (last_basic_block_for_fn (cfun)); > bitmap_clear (in_worklist); >+ bitmap_clear (in_pending); > > /* We're performing the dataflow iteration independently over the > toplevel SCCs plus leading non-cyclic entry blocks and separately
diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c index 743f5dcecf6..52aea47a053 100644 --- a/gcc/var-tracking.c +++ b/gcc/var-tracking.c @@ -7096,6 +7096,7 @@ vt_find_locations (void) in_worklist = sbitmap_alloc (last_basic_block_for_fn (cfun)); in_pending = sbitmap_alloc (last_basic_block_for_fn (cfun)); bitmap_clear (in_worklist); + bitmap_clear (in_pending); /* We're performing the dataflow iteration independently over the toplevel SCCs plus leading non-cyclic entry blocks and separately