[backport gcc10, gcc9] Requet to backport PR97969

[Richard Biener]

On Tue, 2 Feb 2021, Przemyslaw Wirkus wrote:

> > On 2021-01-18 7:50 a.m., Richard Biener wrote:
> > > On Mon, 18 Jan 2021, Przemyslaw Wirkus wrote:
> > >
> > >> Hi all,
> > >>
> > >> Can we backport PR97969 patch to GCC 10 and (maybe) GCC 9 ?:
> > >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97969
> > >>
> > >> IMHO bug is severe and could land in GCC 10 and 9. Vladimir's original
> > patch:
> > >> https://gcc.gnu.org/pipermail/gcc-patches/2021-January/563322.html
> > >> applies without changes to both gcc-10 and gcc-9.
> > >>
> > >> I've regression tested this patch on both gcc-10 and gcc-9 branched
> > >> for
> > >> x86_64 cross (arm-eabi target) and no issues.
> > >>
> > >> OK for gcc-10 and gcc-9 ?
> > > I see two fallout PRs with a trivial search: PR98643 and PR98722.  LRA
> > > patches quite easily trigger unexpected fallout unfortunately ...
> > >
> > Yes, I am agree.  We should wait until the new regressions are fixed.  I am
> > going to work on this patch more to fix the new regressions. Although the
> > basic idea of the original problem solution probably will stay the same.
> 
> I've retested series of three patches which are related to this PR:
> 
> 19af25c0b3aa2a78b4d45d295359ec26cb9fc607 [PR98777]
> 79c57603602c4493b6baa1d47ed451e8f5e9c0f3 [PR98722]
> 34aa56af2547e1646c0f07b9b88b210ebdb2a9f5 [PR97969]
> 
> on top of gcc-10 branch.
> 
> Bootstrapped and regression tested on aarch64-linux-gnu machine and no issues.
> Regression tested on x86_64 host (arm-eabi target) cross and no issues.
> 
> OK for gcc-10 ?

I think this warrants waiting until at least the GCC 11 release.

Richard.