On Thu, Jul 11, 2024 at 2:45 PM YunQiang Su <[email protected]> wrote:
>
> Richard Biener <[email protected]> 于2024年7月11日周四 20:21写道：
> >
> > On Thu, Jul 11, 2024 at 2:13 PM YunQiang Su <[email protected]> wrote:
> > >
> > > From: YunQiang Su <[email protected]>
> > >
> > > 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.
That's quite unlikely in this case but yes, TREE_NO_WARNING is a big hammer.
> > ?
> >
> > > + 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
> > >
