[External] Re: [PATCH] RISC-V: selftests: fix cbo.c compilation error

[yunhui cui]

Hi drew，

On Wed, Jan 17, 2024 at 5:16 PM Andrew Jones <ajones at ventanamicro.com> wrote:
>
> On Wed, Jan 17, 2024 at 04:25:14PM +0800, Yunhui Cui wrote:
> > When compiling with -O0, the following error will occur:
> > cbo.c: In function 'cbo_insn':
> > cbo.c:43:9: warning: 'asm' operand 1 probably does not match constraints
> >    43 |         asm volatile(
> >       |         ^~~
> > cbo.c:43:9: warning: 'asm' operand 2 probably does not match constraints
> > cbo.c:43:9: error: impossible constraint in 'asm'
> >
> > Add __attribute__((optimize("O"))) to fix.
> >
> > Fixes: a29e2a48afe3 ("RISC-V: selftests: Add CBO tests")
> > Signed-off-by: Yunhui Cui <cuiyunhui at bytedance.com>
> > Suggested-by: Zhipeng Xu <xuzhipeng.1973 at bytedance.com>
> > ---
> >  tools/testing/selftests/riscv/hwprobe/cbo.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/testing/selftests/riscv/hwprobe/cbo.c b/tools/testing/selftests/riscv/hwprobe/cbo.c
> > index 50a2cc8aef38..ff1d8e843d70 100644
> > --- a/tools/testing/selftests/riscv/hwprobe/cbo.c
> > +++ b/tools/testing/selftests/riscv/hwprobe/cbo.c
> > @@ -36,7 +36,7 @@ static void sigill_handler(int sig, siginfo_t *info, void *context)
> >       regs[0] += 4;
> >  }
> >
> > -static void cbo_insn(char *base, int fn)
> > +static __always_inline void cbo_insn(char *base, int fn)
> >  {
> >       uint32_t insn = MK_CBO(fn);
> >
> > @@ -47,10 +47,11 @@ static void cbo_insn(char *base, int fn)
> >       : : "r" (base), "i" (fn), "i" (insn) : "a0", "a1", "memory");
> >  }
> >
> > -static void cbo_inval(char *base) { cbo_insn(base, 0); }
> > -static void cbo_clean(char *base) { cbo_insn(base, 1); }
> > -static void cbo_flush(char *base) { cbo_insn(base, 2); }
> > -static void cbo_zero(char *base)  { cbo_insn(base, 4); }
> > +#define OPTIMIZE __attribute__((optimize("O")))
> > +OPTIMIZE static void cbo_inval(char *base) { cbo_insn(base, 0); }
> > +OPTIMIZE static void cbo_clean(char *base) { cbo_insn(base, 1); }
> > +OPTIMIZE static void cbo_flush(char *base) { cbo_insn(base, 2); }
> > +OPTIMIZE static void cbo_zero(char *base)  { cbo_insn(base, 4); }
> >
> >  static void test_no_zicbom(void *arg)
> >  {
> > --
> > 2.20.1
> >
>
> Hi Yunhui,
>
> Thanks for the bug report, but this isn't the right fix. The real problem
> is that I didn't ensure operands 1 and 2 match their constraints, just as
> the warning you discovered says. To do that, I should have made cbo_insn()
> a macro and not used the local variable, i.e. ensure 'fn' and 'insn' are
> indeed constants derived from the 0,1,2,4 constants.
>
> I'll send a patch with your reported-by.
Okay, if you want to use macros to fix it, you can. thanks！

Thanks，
Yunhui