Re: [PATCH] s390/test_unwind: use raw opcode instead of invalid instruction

[Christian Borntraeger]

Am 19.11.21 um 10:39 schrieb Christian Borntraeger:
> Am 19.11.21 um 02:10 schrieb Nick Desaulniers:
> > On Wed, Nov 17, 2021 at 9:48 AM Ilie Halip <ilie.halip@xxxxxxxxx> wrote:
> > > Building with clang & LLVM_IAS=1 leads to an error:
> > >      arch/s390/lib/test_unwind.c:179:4: error: invalid register pair
> > >                          "       mvcl    %%r1,%%r1\n"
> > >                          ^
> > >
> > > The test creates an invalid instruction that would trap at runtime, but the
> > > LLVM inline assembler tries to validate it at compile time too.
> > >
> > > Use the raw instruction opcode instead.
> > >
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/1421
> > > Reported-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > > Signed-off-by: Ilie Halip <ilie.halip@xxxxxxxxx>
> >
> > Ilie, thanks for the patch!
> >
> > So if I understand
> > https://sourceware.org/binutils/docs/as/s390-Directives.html#s390-Directives
> > https://sourceware.org/binutils/docs/as/s390-Formats.html
> > that `e,` prefix is for 16B opcodes?
>
> e is an instruction format as specified by the architecture.
> See http://publibfp.dhe.ibm.com/epubs/pdf/a227832c.pdf

(page 5-3 for the instruction formats and page 7-289 for MVCL)