> On Fri, Dec 10, 2021 at 2:30 AM Roger Sayle <ro...@nextmovesoftware.com>
> wrote:
> >
> >
> > This patch fixes PR ipa/103061 which is P1 regression that shows up as
> > an ICE in ipa-modref-tree.c's insert_kill when compiling the CSiBE
> > benchmark. I believe the underlying cause is that the new kill tracking
> > functionality wasn't anticipating memory accesses that are zero bits
> > wide!?. The failing source code (test case) contains the unusual lines:
> > typedef struct { } spinlock_t;
> > and
> > q->lock = (spinlock_t) { };
> > Making spinlock_t larger, or removing the assignment work around the issue.
>
> zero sized accesses (load and stores) should have been removed during
> gimplification. Why was it not?
Sadly this does not happen systematically... I already had to fix
similar issue with load/store analysis in modref :(
> >
> > 2021-12-10 Roger Sayle <ro...@nextmovesoftware.com>
> >
> > gcc/ChangeLog
> > PR ipa/103601
> > * ipa-modref-tree.h (useful_for_kill_p): Zero width accesses aren't
> > useful for kill tracking.
The patch is OK. Even if we make gimplifier smarter about zero width
accesses I guess we want to be safe that they are not synthetized from
i.e. variable sized arrays.
Thanks for fixing this!
Honza
> >
> > gcc/testsuite/ChangeLog
> > PR ipa/103601
> > * gcc.dg/ipa/pr103601.c: New test case.
> >
> > Thanks in advance,
> > Roger
> > --
> >
