On Mon, Jun 30, 2025 at 11:46 AM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> On Mon, Jun 30, 2025 at 11:17 AM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > On Mon, Jun 30, 2025 at 10:41 AM Hongtao Liu <crazy...@gmail.com> wrote:
> > >
> > > On Mon, Jun 30, 2025 at 10:37 AM Hongtao Liu <crazy...@gmail.com> wrote:
> > > >
> > > > On Sat, Jun 28, 2025 at 8:30 PM H.J. Lu <hjl.to...@gmail.com> wrote:
> > > > >
> > > > > Update functions with no_callee_saved_registers/preserve_none
> > > > > attribute
> > > > > to preserve frame pointer since caller may use it to save the current
> > > > > stack:
> > > > >
> > > > > pushq %rbp
> > > > > movq %rsp, %rbp
> > > > > ...
> > > > > call function
> > > > > ...
> > > > > leave
> > > > > ret
> > > > >
> > > > > If callee changes frame pointer without restoring it, caller will fail
> > > > > to restore its stack after callee returns.
> > > > Do we know why the caller failed to restore rbp? Are there any
> > > > assumptions in the middle-end that frame pointers must be callee saved
> > > > registers(even if it's marked as caller-saved)?
> > > >
> > > > >
> > > >
> > > > /* The current function is a function specified with the
> > > > "no_callee_saved_registers" attribute. */
> > > > TYPE_NO_CALLEE_SAVED_REGISTERS,
> > > > - /* The current function is a function specified with the "noreturn"
> > > > - attribute. */
> > > > - TYPE_NO_CALLEE_SAVED_REGISTERS_EXCEPT_BP,
> > > >
> > > > Comments of "noreturn" part should be merged into that of
> > > > TYPE_NO_CALLEE_SAVED_REGISTERS.
> > > >
> > > > +callee-saved registers. That is, all registers, except for stack and
> > > > +frame pointers, can be used as scratch registers. For example, this
> > > >
> > > > The patch only excludes frame pointers but the document mentions both
> > > > stack and frame pointers?
> > >
> > > And documents of preserve_none attribute should be changed since your
> > > patch also exclude frame_pointer for TYPE_PRESERVE_NONE.
> >
> > Since preserve_none is documented as
> >
> > This attribute is similar to @code{no_callee_saved_registers}, except
> > on x86-64, r12, r13, r14, r15, rdi and rsi registers are used for
> > integer parameter passing and this calling convention is subject to
> > change.
> >
> > no_callee_saved_registers covers preserve_none on frame pointer.
> >
> > > case TYPE_NO_CALLEE_SAVED_REGISTERS:
> > > case TYPE_PRESERVE_NONE:
> > > - return false;
> > > -
> > > - case TYPE_NO_CALLEE_SAVED_REGISTERS_EXCEPT_BP:
> > > if (regno != HARD_FRAME_POINTER_REGNUM)
> > > return false;
>
> Here is the v2 patch. The only change is
>
> enum call_saved_registers_type
> {
> TYPE_DEFAULT_CALL_SAVED_REGISTERS = 0,
> /* The current function is a function specified with the "interrupt"
> or "no_caller_saved_registers" attribute. */
> TYPE_NO_CALLER_SAVED_REGISTERS,
> /* The current function is a function specified with the
> "no_callee_saved_registers" attribute or a function specified with
> the "noreturn" attribute when compiled with
> "-mnoreturn-no-callee-saved-registers". */
> TYPE_NO_CALLEE_SAVED_REGISTERS,
> /* The current function is a function specified with the
> "preserve_none" attribute. */
> TYPE_PRESERVE_NONE,
> };
>
> OK for master?
Ok.
>
> Thanks.
>
> --
> H.J.
--
BR,
Hongtao
