On Mon, Jan 29, 2024 at 8:30 AM Jakub Jelinek <ja...@redhat.com> wrote:
>
> On Mon, Jan 29, 2024 at 08:00:26AM -0800, H.J. Lu wrote:
> > Attach REG_CFA_UNDEFINED notes for unsaved callee-saved registers which
> > have been used in the function to an instruction in prologue.
> >
> > gcc/
> >
> > PR target/38534
> > * dwarf2cfi.cc (add_cfi_undefined): New.
> > (dwarf2out_frame_debug_cfa_undefined): Likewise.
> > (dwarf2out_frame_debug): Handle REG_CFA_UNDEFINED.
> > * reg-notes.def (REG_CFA_UNDEFINED): New.
> > * config/i386/i386.cc (ix86_expand_prologue): Attach
> > REG_CFA_UNDEFINED notes for unsaved callee-saved registers
> > which have been used in the function to an instruction in
> > prologue.
> >
> > gcc/testsuite/
> >
> > PR target/38534
> > * gcc.target/i386/no-callee-saved-19.c: New test.
> > * gcc.target/i386/no-callee-saved-20.c: Likewise.
> > * gcc.target/i386/pr38534-7.c: Likewise.
> > * gcc.target/i386/pr38534-8.c: Likewise.
> > ---
> > gcc/config/i386/i386.cc | 20 +++++++
> > gcc/dwarf2cfi.cc | 55 +++++++++++++++++++
> > gcc/reg-notes.def | 4 ++
> > .../gcc.target/i386/no-callee-saved-19.c | 17 ++++++
> > .../gcc.target/i386/no-callee-saved-20.c | 12 ++++
> > gcc/testsuite/gcc.target/i386/pr38534-7.c | 18 ++++++
> > gcc/testsuite/gcc.target/i386/pr38534-8.c | 13 +++++
> > 7 files changed, 139 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.target/i386/no-callee-saved-19.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/no-callee-saved-20.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr38534-7.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr38534-8.c
> >
> > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> > index b3e7c74846e..6ec87b6a16f 100644
> > --- a/gcc/config/i386/i386.cc
> > +++ b/gcc/config/i386/i386.cc
> > @@ -9304,6 +9304,26 @@ ix86_expand_prologue (void)
> > combined with prologue modifications. */
> > if (TARGET_SEH)
> > emit_insn (gen_prologue_use (stack_pointer_rtx));
> > +
> > + if (cfun->machine->call_saved_registers
> > + != TYPE_NO_CALLEE_SAVED_REGISTERS)
> > + return;
> > +
> > + insn = get_insns ();
> > + if (!insn)
> > + return;
>
> You can't attach the notes to a random instruction that happens to be first
> in the function.
> 1) it needs to be a real instruction, not a note
Will fix it.
> 2) it needs to be RTX_FRAME_RELATED_P
This should work:
insn = nullptr;
rtx_insn *next;
for (next = get_insns (); next; next = NEXT_INSN (next))
{
if (!RTX_FRAME_RELATED_P (next))
continue;
insn = next;
}
if (!insn)
return;
> 3) if it is RTX_FRAME_RELATED_P, but doesn't contain any previous REG_CFA_*
> notes:
> 3a) if it has REG_FRAME_RELATED_EXPR note, then I believe just that
> note argument is processed instead of the instruction pattern and
> I think REG_CFA_* notes which precede REG_FRAME_RELATED_EXPR are
> processed, but REG_CFA_* notes after it are not; so adding
> REG_CFA_UNDEFINED notes at least if the adding is after the existing
> notes instead of before them may be problematic
Since register note is added to the head:
/* Add register note with kind KIND and datum DATUM to INSN. */
void
add_reg_note (rtx insn, enum reg_note kind, rtx datum)
{
REG_NOTES (insn) = alloc_reg_note (kind, datum, REG_NOTES (insn));
}
it isn't an issue.
> 3b) if it has neither REG_CFA_* nor REG_FRAME_RELATED_EXPR notes, then
> normally the pattern of the insn would be processed in dwarf2cfi.
> But with the REG_CFA_* notes that part will be ignored.
>
> > --- a/gcc/dwarf2cfi.cc
> > +++ b/gcc/dwarf2cfi.cc
> > @@ -517,6 +517,17 @@ add_cfi_restore (unsigned reg)
> > add_cfi (cfi);
> > }
> >
>
> Function comment missing.
Will fix it in the v3 patch.
Thanks.
> > +static void
> > +add_cfi_undefined (unsigned reg)
> > +{
> > + dw_cfi_ref cfi = new_cfi ();
> > +
> > + cfi->dw_cfi_opc = DW_CFA_undefined;
> > + cfi->dw_cfi_oprnd1.dw_cfi_reg_num = reg;
> > +
> > + add_cfi (cfi);
> > +}
> > +
> > /* Perform ROW->REG_SAVE[COLUMN] = CFI. CFI may be null, indicating
> > that the register column is no longer saved. */
>
> Jakub
>
--
H.J.
