Re: [PATCH] RISC-V: Save/restore ra register correctly [PR112478]

[Kito Cheng <kito.cheng@gmail.com>]

Committed, thanks for the review and test :)

On Thu, Nov 16, 2023 at 7:19 AM Christoph Müllner
<christoph.muellner@vrull.eu> wrote:
>
> On Tue, Nov 14, 2023 at 3:15 PM Kito Cheng <kito.cheng@sifive.com> wrote:
> >
> > We set ra to fixed register now, but we still need to save/restore that at
> > prologue/epilogue if that has used.
>
> So before 71f906498ada9 $ra was neither a fixed nor a used register.
> Therefore, riscv_save_reg_p returned true in the first test (not global reg,
> not used_or_fixed, and ever_live_p).
> After this commit, this does not happen anymore, because the test for
> not used_or_fixed fails and we don't test for ever_live_p in the following.
> And this patch restores this behavior.
>
> Reviewed-by: Christoph Müllner <christoph.muellner@vrull.eu>
> Tested-by: Christoph Müllner <christoph.muellner@vrull.eu>
>
> >
> > gcc/ChangeLog:
> >
> >         PR target/112478
> >         * config/riscv/riscv.cc (riscv_save_return_addr_reg_p): Check ra
> >         is ever lived.
> >
> > gcc/testsuite/gcc/ChangeLog:
> >
> >         PR target/112478
> >         * riscv/pr112478.c: New.
> > ---
> >  gcc/config/riscv/riscv.cc                 | 4 ++++
> >  gcc/testsuite/gcc.target/riscv/pr112478.c | 8 ++++++++
> >  2 files changed, 12 insertions(+)
> >  create mode 100644 gcc/testsuite/gcc.target/riscv/pr112478.c
> >
> > diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
> > index ecee7eb4727..f09c4066903 100644
> > --- a/gcc/config/riscv/riscv.cc
> > +++ b/gcc/config/riscv/riscv.cc
> > @@ -5802,6 +5802,10 @@ riscv_save_return_addr_reg_p (void)
> >    if (riscv_far_jump_used_p ())
> >      return true;
> >
> > +  /* We need to save it if anyone has used that.  */
> > +  if (df_regs_ever_live_p (RETURN_ADDR_REGNUM))
> > +    return true;
> > +
> >    /* Need not to use ra for leaf when frame pointer is turned off by
> >       option whatever the omit-leaf-frame's value.  */
> >    if (frame_pointer_needed && crtl->is_leaf
> > diff --git a/gcc/testsuite/gcc.target/riscv/pr112478.c b/gcc/testsuite/gcc.target/riscv/pr112478.c
> > new file mode 100644
> > index 00000000000..0bbde20b71b
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/riscv/pr112478.c
> > @@ -0,0 +1,8 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-ffat-lto-objects" } */
> > +
> > +void foo() {
> > +    asm volatile("# " : ::"ra");
> > +}
> > +
> > +/* { dg-final { scan-assembler "s(w|d)\[ \t\]*ra" } } */
> > --
> > 2.40.1
> >