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> -----Original Message-----
> From: Alex Coplan <alex.cop...@arm.com>
> Sent: Monday, January 6, 2025 11:35 AM
> To: gcc-patches@gcc.gnu.org
> Cc: Richard Biener <rguent...@suse.de>; Jan Hubicka <hubi...@ucw.cz>; Tamar
> Christina <tamar.christ...@arm.com>
> Subject: [PATCH 3/4] vect: Ensure profile consistency when adding epilog guard
> [PR117790]
>
> This patch tries to make the CFG profile consistent when adding a guard
> edge to skip the epilog during peeling.
>
> The changes can be summarized as follows:
> - We avoid adding the guard edge entirely if the guard condition folds
> to false, otherwise the profile will become inconsistent since
> the cfgcleanup code doesn't attempt to update it on removing the dead
> edge.
> - If the guard condition instead folds to true, we account for this by
> giving the skip edge 100% probability (otherwise the profile will
> again become inconsistent when removing the other now-dead edge).
> - Finally, we use the new helper scale_loop_freqs_with_new_exit_count instead
> of scale_loop_profile to update the epilog frequencies / probabiltiies.
> We make the assumption here that if the IV exit is taken in the vector
> loop,
> then it will also be taken in the epilog (and not an early exit). Since we
> add the guard to the vector iv exit, we know any reduction in count
> associated with the epilog skip should be accounted for by a reduction in
> the
> epilog's iv exit edge count.
>
> Bootstrapped/regtested as a series on aarch64-linux-gnu, arm-linux-gnueabihf,
> and x86_64-linux-gnu. OK for trunk?
>
> Thanks,
> Alex
>
> gcc/ChangeLog:
>
> PR tree-optimization/117790
> * tree-vect-loop-manip.cc (vect_do_peeling): Attempt to maintain
> consistency of the CFG profile when adding an epilog skip edge.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/117790
> * gcc.dg/vect/vect-early-break-profile-1.c: New test.
> ---
> .../gcc.dg/vect/vect-early-break-profile-1.c | 10 ++++
> gcc/tree-vect-loop-manip.cc | 48 ++++++++++++++-----
> 2 files changed, 47 insertions(+), 11 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-early-break-profile-1.c
