On Mon, 24 Aug 2020, Jakub Jelinek wrote:
> Hi!
>
> Clobbers of MEM_REF with NULL address are just fancy nops, something we just
> ignore and don't emit any code for it (ditto for other clobbers), they just
> mark end of life on something, so we shouldn't infer from those that there
> is some UB.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2020-08-24 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/96722
> * gimple.c (infer_nonnull_range): Formatting fix.
> (infer_nonnull_range_by_dereference): Return false for clobber stmts.
>
> * g++.dg/opt/pr96722.C: New test.
>
> --- gcc/gimple.c.jj 2020-08-03 22:54:51.417531677 +0200
> +++ gcc/gimple.c 2020-08-24 13:23:22.082312349 +0200
> @@ -2917,8 +2917,8 @@ check_loadstore (gimple *, tree op, tree
> bool
> infer_nonnull_range (gimple *stmt, tree op)
> {
> - return infer_nonnull_range_by_dereference (stmt, op)
> - || infer_nonnull_range_by_attribute (stmt, op);
> + return (infer_nonnull_range_by_dereference (stmt, op)
> + || infer_nonnull_range_by_attribute (stmt, op));
> }
>
> /* Return true if OP can be inferred to be non-NULL after STMT
> @@ -2930,7 +2930,8 @@ infer_nonnull_range_by_dereference (gimp
> non-NULL if -fdelete-null-pointer-checks is enabled. */
> if (!flag_delete_null_pointer_checks
> || !POINTER_TYPE_P (TREE_TYPE (op))
> - || gimple_code (stmt) == GIMPLE_ASM)
> + || gimple_code (stmt) == GIMPLE_ASM
> + || gimple_clobber_p (stmt))
> return false;
>
> if (walk_stmt_load_store_ops (stmt, (void *)op,
> --- gcc/testsuite/g++.dg/opt/pr96722.C.jj 2020-08-24 13:24:45.357132323
> +0200
> +++ gcc/testsuite/g++.dg/opt/pr96722.C 2020-08-24 13:25:06.224836626
> +0200
> @@ -0,0 +1,20 @@
> +// PR tree-optimization/96722
> +// { dg-do run }
> +// { dg-options "-O2" }
> +
> +struct S { int s; ~S () {} };
> +
> +void
> +foo (S *a)
> +{
> + if (a)
> + return;
> + a->~S ();
> +}
> +
> +int
> +main ()
> +{
> + S s;
> + foo (&s);
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
