Hi,
On Fri, Jun 10 2022, Jan Hubicka wrote:
> Hi,
> this patch prevents ipa-prop from propagating aggregates when load is
> volatile. Martin, does this look OK? It seem to me that ipa-prop may
> need some additional volatile flag checks.
load_from_unmodified_param_or_agg checks for it, although at a bit weird
place (quite late and it looks like volatile reads from an aggregate
parameter passed by value might still be considered OK). Building of
IPA_JF_LOAD_AGG jump functions also checks for it.
compute_complex_assign_jump_func and get_ancestor_addr_info look at
mem_refs in addr_exprs, so that should be safe.
>From a quick scan of ipa-prop, it seems that only ipa_load_from_parm_agg
missed it (modulo the parenthesis above).
>
> Bootstrapped/regtested x86_64-linux, OK?
Sure, OK, thanks!
Martin
> gcc/ChangeLog:
>
> 2022-06-10 Jan Hubicka <hubi...@ucw.cz>
>
> PR ipa/105739
> * ipa-prop.cc (ipa_load_from_parm_agg): Disqualify volatile memory
> accesses.
>
> gcc/testsuite/ChangeLog:
>
> 2022-06-10 Jan Hubicka <hubi...@ucw.cz>
>
> * gcc.dg/ipa/pr105739.c: New test.
>
> diff --git a/gcc/ipa-prop.cc b/gcc/ipa-prop.cc
> index afd9222b5a2..c037668e7d8 100644
> --- a/gcc/ipa-prop.cc
> +++ b/gcc/ipa-prop.cc
> @@ -1112,6 +1112,10 @@ ipa_load_from_parm_agg (struct ipa_func_body_info *fbi,
> if (!base)
> return false;
>
> + /* We can not propagate across volatile loads. */
> + if (TREE_THIS_VOLATILE (op))
> + return false;
> +
> if (DECL_P (base))
> {
> int index = ipa_get_param_decl_index_1 (descriptors, base);
> diff --git a/gcc/testsuite/gcc.dg/ipa/pr105739.c
> b/gcc/testsuite/gcc.dg/ipa/pr105739.c
> new file mode 100644
> index 00000000000..8dbe8fc2494
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/pr105739.c
> @@ -0,0 +1,30 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +
> +__attribute__((noinline))
> +static int
> +test2(int a)
> +{
> + if (__builtin_constant_p (a))
> + __builtin_abort ();
> + return a;
> +}
> +static int
> +test(int *a)
> +{
> + int val = *(volatile int *)a;
> + if (__builtin_constant_p (val))
> + __builtin_abort ();
> + if (val)
> + return test2(val);
> + return 0;
> +}
> +int a;
> +int
> +main()
> +{
> + a = 0;
> + return test (&a);
> +}
> +/* { dg-final { scan-tree-dump "test2" "optimized" } } */
