Richard Biener <richard.guent...@gmail.com> 于2024年7月11日周四 20:21写道：
>
> On Thu, Jul 11, 2024 at 2:13 PM YunQiang Su <s...@gcc.gnu.org> wrote:
> >
> > From: YunQiang Su <yunqi...@isrc.iscas.ac.cn>
> >
> > PR target/115840.
> >
> > In riscv_preferred_else_value, we create an uninitialized tmp var
> > for else value, instead of the 0 (as default_preferred_else_value)
> > or the pre-exists VAR (as aarch64 does), so that we can use agnostic
> > policy.
> >
> > The problem is that `warn_uninit` will emit a warning:
> > ({anonymous})’ may be used uninitialized
> >
> > Let's mark this tmp var as "allow_uninitialized".
> >
> > This problem is found when I try to build glibc with V extension.
> >
> > gcc
> > PR target/115840.
> > * config/riscv/riscv.cc(riscv_preferred_else_value): Mark
> > tmp_var as allow_unitialized.
> >
> > gcc/testsuite
> > * gcc.dg/vect/pr115840.c: New testcase.
> > ---
> > gcc/config/riscv/riscv.cc | 6 +++++-
> > gcc/testsuite/gcc.dg/vect/pr115840.c | 11 +++++++++++
> > 2 files changed, 16 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/gcc.dg/vect/pr115840.c
> >
> > diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
> > index 61fa74e9322..08159d7cbbc 100644
> > --- a/gcc/config/riscv/riscv.cc
> > +++ b/gcc/config/riscv/riscv.cc
> > @@ -11431,7 +11431,11 @@ riscv_preferred_else_value (unsigned ifn, tree
> > vectype, unsigned int nops,
> > tree *ops)
> > {
> > if (riscv_v_ext_mode_p (TYPE_MODE (vectype)))
> > - return get_or_create_ssa_default_def (cfun, create_tmp_var (vectype));
> > + {
> > + tree tmp_var = create_tmp_var (vectype);
> > + TREE_ALLOW_UNINITIALIZED (tmp_var) = 1;
>
> Does it work when you do
>
> TREE_NO_WARNING (tmp_var) = 1;
>
Thanks. It works. I did notice it, while I worried that there may be
some other
warnings, that TREE_NO_WARNING may cover them.
> ?
>
> > + return get_or_create_ssa_default_def (cfun, tmp_var);
> > + }
> >
> > return default_preferred_else_value (ifn, vectype, nops, ops);
> > }
> > diff --git a/gcc/testsuite/gcc.dg/vect/pr115840.c
> > b/gcc/testsuite/gcc.dg/vect/pr115840.c
> > new file mode 100644
> > index 00000000000..09dc9e4eb7c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/pr115840.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-additional-options "-Wall -Werror" } */
> > +
> > +double loads[16];
> > +
> > +void
> > +foo (double loadavg[], int count)
> > +{
> > + for (int i = 0; i < count; i++)
> > + loadavg[i] = loads[i] / 1.5;
> > +}
> > --
> > 2.45.1
> >
