Re: PR90724 - ICE with __sync_bool_compare_and_swap with -march=armv8.2-a

[Prathamesh Kulkarni <prathamesh dot kulkarni at linaro dot org>]

On Thu, 25 Jul 2019 at 11:56, Prathamesh Kulkarni
<prathamesh.kulkarni@linaro.org> wrote:
>
> On Wed, 17 Jul 2019 at 18:15, Prathamesh Kulkarni
> <prathamesh.kulkarni@linaro.org> wrote:
> >
> > On Wed, 17 Jul 2019 at 13:45, Kyrill Tkachov
> > <kyrylo.tkachov@foss.arm.com> wrote:
> > >
> > > Hi Prathamesh
> > >
> > > On 7/10/19 12:24 PM, Prathamesh Kulkarni wrote:
> > > > Hi,
> > > > For following test-case,
> > > > static long long AL[24];
> > > >
> > > > int
> > > > check_ok (void)
> > > > {
> > > >   return (__sync_bool_compare_and_swap (AL+1, 0x200000003ll,
> > > > 0x1234567890ll));
> > > > }
> > > >
> > > > Compiling with -O2 -march=armv8.2-a results in:
> > > > pr90724.c: In function ‘check_ok’:
> > > > pr90724.c:7:1: error: unrecognizable insn:
> > > >     7 | }
> > > >       | ^
> > > > (insn 11 10 12 2 (set (reg:CC 66 cc)
> > > >         (compare:CC (reg:DI 95)
> > > >             (const_int 8589934595 [0x200000003]))) "pr90724.c":6:11 -1
> > > >      (nil))
> > > >
> > > > IIUC, the issue is that 0x200000003 falls outside the range of
> > > > allowable immediate in cmp ? If it's replaced by a small constant then
> > > > it works.
> > > >
> > > > The ICE results with -march=armv8.2-a because, we enter if
> > > > (TARGET_LSE) { ... } condition
> > > > in aarch64_expand_compare_and_swap, while with -march=armv8.a it goes
> > > > into else,
> > > > which forces oldval into register if the predicate fails to match.
> > > >
> > > > The attached patch checks if y (oldval) satisfies aarch64_plus_operand
> > > > predicate and if not, forces it to be in register, which resolves ICE.
> > > > Does it look OK ?
> > > >
> > > > Bootstrap+testing in progress on aarch64-linux-gnu.
> > > >
> > > > PS: The issue has nothing to do with SVE, which I incorrectly
> > > > mentioned in bug report.
> > > >
> > > This looks ok to me (but you'll need maintainer approval).
> > >
> > > Does this fail on the branches as well?
> > Hi Kyrill,
> > Thanks for the review. The test also fails on gcc-9-branch (but not on gcc-8).
> Hi James,
> Is the patch OK to commit  ?
> https://gcc.gnu.org/ml/gcc-patches/2019-07/msg00793.html
ping * 3: https://gcc.gnu.org/ml/gcc-patches/2019-07/msg00793.html

Thanks,
Prathamesh
>
> Thanks,
> Prathamesh
> >
> > Thanks,
> > Prathamesh
> > >
> > > Thanks,
> > >
> > > Kyrill
> > >
> > >
> > > > Thanks,
> > > > Prathamesh