On Tue, Aug 4, 2026 at 2:39 AM Kugan Vivekanandarajah <
[email protected]> wrote:
> PHI arguments are indexed by incoming edges. function_instance::match
> walked successor edges and could fail gimple_phi_arg_def_from_edge's
> destination assertion during afdo_offline.
>
> gcc/ChangeLog:
>
> * auto-profile.cc (function_instance::match): Walk predecessor
> edges
> for PHI arguments.
>
This is OK. It is really strange this does not trigger checking failure
I see that
inline location_t
gimple_phi_arg_location_from_edge (gphi *phi, edge e)
{
return gimple_phi_arg (phi, e->dest_idx)->locus;
Does not check that PHI BB and e->dest match (that looks like omission that
would be useful to fix), but still we should eventually hit out of range
access which is checked in gimple_phi_arg.
Honza
>
> Regression tested on aarch64-linux-gnu with no new regressions
>
> Signed-off-by: Kugan Vivekanandarajah <[email protected]>
> ---
> gcc/auto-profile.cc | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/auto-profile.cc b/gcc/auto-profile.cc
> index f4562d7f2f98..60f6b1ba480b 100644
> --- a/gcc/auto-profile.cc
> +++ b/gcc/auto-profile.cc
> @@ -1764,7 +1764,8 @@ function_instance::match (cgraph_node *node,
> gcc_assert (!info);
> dump_stmt (phi, info, NULL, stack);
> counts.add (info);
> - for (edge e : bb->succs)
> + /* PHI arguments are indexed by incoming (predecessor) edges. */
> + for (edge e : bb->preds)
> {
> location_t phi_loc
> = gimple_phi_arg_location_from_edge (phi, e);
> --
> 2.34.1
>
>
