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


> -----Original Message-----
> From: gcc-patches-owner@gcc.gnu.org <gcc-patches-owner@gcc.gnu.org> On
> Behalf Of Prathamesh Kulkarni
> Sent: Thursday, August 22, 2019 2:36 AM
> To: James Greenhalgh <james.greenhalgh@arm.com>
> Cc: gcc Patches <gcc-patches@gcc.gnu.org>; Richard Sandiford
> <Richard.Sandiford@arm.com>; Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>;
> nd <nd@arm.com>
> Subject: Re: PR90724 - ICE with __sync_bool_compare_and_swap with -
> march=armv8.2-a
> 
> On Mon, 19 Aug 2019 at 22:14, James Greenhalgh
> <james.greenhalgh@arm.com> wrote:
> >
> > On Thu, Aug 15, 2019 at 02:11:25PM +0100, Prathamesh Kulkarni wrote:
> > > On Thu, 8 Aug 2019 at 11:22, Prathamesh Kulkarni
> > > <prathamesh.kulkarni@linaro.org> wrote:
> > > >
> > > > On Thu, 1 Aug 2019 at 15:34, Prathamesh Kulkarni
> > > > <prathamesh.kulkarni@linaro.org> wrote:
> > > > >
> > > > > 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
> > > > ping * 4: https://gcc.gnu.org/ml/gcc-patches/2019-07/msg00793.html
> > > ping * 5: https://gcc.gnu.org/ml/gcc-patches/2019-07/msg00793.html
> >
> > Hi,
> >
> > Sorry, this missed my filters as it didn't mention AArch64 in the
> > subject line.
> >
> > Thais is good for trunk, thanks for waiting.
> Thanks, committed to trunk in r274805.

Trunk aarch64 build failure is exposed by this commit.

../../gcc/gcc/config/aarch64/aarch64.c: In function ���bool aarch64_evpc_sel(expand_vec_perm_d*)���:
../../gcc/gcc/config/aarch64/aarch64.c:18018:75: error: ���gen_vcond_mask��� was not declared in this scope
   emit_insn (gen_vcond_mask (vmode, vmode, d->target, d->op1, d->op0, pred));
                                                                           ^
make[3]: *** [aarch64.o] Error 1
make[3]: Leaving directory `/home/amptest/gcc/build/gcc'

> Is this OK to backport to gcc-9-branch ?
> 
> Thanks,
> Prathamesh
> >
> > James
> >

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