frame_pointer_needed always true ?

[Aurélien Buhrig <aurelien.buhrig.gcc@xxxxxxxxx>]

Hi,

I'm porting a private backend from an old 4.6 gcc to the 6.1.0 release,
and would appreciate an little help figuring out what may be wrong.

In my backend prologue (6.1.0 release), I test frame_pointer_needed to
figure out if the frame pointer is needed or not. But
frame_pointer_needed is always true (even the function void f(void) {}
which does not use any register), unless setting -fomit_frame_pointer.

The TARGET_FRAME_POINTER_REQUIRED is defined to hook_bool_void_false,
and the INITIAL_ELIMINATION_OFFSET, ELIMINABLE_REGS and
TARGET_CAN_ELIMINATE seem to be correctly defined and elimination works
correctly with -fomit-frame-pointer.
I noticed that both my frame pointer and the stack pointer are marked
live in; lr in and lr use for this empty function (post reload). I
wonder if it is normal.

Thanks in advance!
Aurélien