[Aarch64] Make frame grow downwards

Hi,
Following the discussion on
http://gcc.gnu.org/ml/gcc/2013-05/msg00208.html
here is a patch to change the frame direction.

Passed 'make check' with no regression on aarch64-none-linux-gnu and
with a few UNSUPPORTED -> PASS on aarch64-none-elf (pr34225, pr38616,
pr38902, pr40971, pr46440, pr47766, pr49307, all of which are guarded
by dg-require-effective-target fstack_protector).

OK for trunk?

Thanks,

Christophe.
2013-06-28  Christophe Lyon  <christophe.lyon@linaro.org>

* config/aarch64/aarch64.h (FRAME_GROWS_DOWNWARD): Define to 1.
* config/aarch64/aarch64.c (aarch64_initial_elimination_offset):
Add get_frame_size () when eliminating frame pointer.

Hi,

Following our discussions about changing the frame direction on
aarch64, I have written a small test case using a large frame which
shows similar code generation with and without my patch. There
are small differences in register allocation which lead to larger
prologue/epilogue with my patch, but I think this could (should) be
improved independently.

I have attached the sample C source and the code generated with
(frane64.s.O2) and without (frame64.s.O2.ref) my patch when compiling
at -O2.

What do you think?

Thanks,

Christophe.

On 28 June 2013 13:41, Christophe Lyon <christophe.lyon@linaro.org> wrote:
> Hi,
> Following the discussion on
> http://gcc.gnu.org/ml/gcc/2013-05/msg00208.html
> here is a patch to change the frame direction.
>
> Passed 'make check' with no regression on aarch64-none-linux-gnu and
> with a few UNSUPPORTED -> PASS on aarch64-none-elf (pr34225, pr38616,
> pr38902, pr40971, pr46440, pr47766, pr49307, all of which are guarded
> by dg-require-effective-target fstack_protector).
>
> OK for trunk?
>
> Thanks,
>
> Christophe.
> 2013-06-28  Christophe Lyon  <christophe.lyon@linaro.org>
>
> * config/aarch64/aarch64.h (FRAME_GROWS_DOWNWARD): Define to 1.
> * config/aarch64/aarch64.c (aarch64_initial_elimination_offset):
> Add get_frame_size () when eliminating frame pointer.

Ping?

The original post is here:
http://gcc.gnu.org/ml/gcc-patches/2013-06/msg01588.html

Thanks,

Christophe.


On 28 June 2013 13:41, Christophe Lyon <christophe.lyon@linaro.org> wrote:
> Hi,
> Following the discussion on
> http://gcc.gnu.org/ml/gcc/2013-05/msg00208.html
> here is a patch to change the frame direction.
>
> Passed 'make check' with no regression on aarch64-none-linux-gnu and
> with a few UNSUPPORTED -> PASS on aarch64-none-elf (pr34225, pr38616,
> pr38902, pr40971, pr46440, pr47766, pr49307, all of which are guarded
> by dg-require-effective-target fstack_protector).
>
> OK for trunk?
>
> Thanks,
>
> Christophe.
> 2013-06-28  Christophe Lyon  <christophe.lyon@linaro.org>
>
> * config/aarch64/aarch64.h (FRAME_GROWS_DOWNWARD): Define to 1.
> * config/aarch64/aarch64.c (aarch64_initial_elimination_offset):
> Add get_frame_size () when eliminating frame pointer.

On 28/06/13 12:41, Christophe Lyon wrote:
> Hi,
> Following the discussion on
> http://gcc.gnu.org/ml/gcc/2013-05/msg00208.html
> here is a patch to change the frame direction.
> 
> Passed 'make check' with no regression on aarch64-none-linux-gnu and
> with a few UNSUPPORTED -> PASS on aarch64-none-elf (pr34225, pr38616,
> pr38902, pr40971, pr46440, pr47766, pr49307, all of which are guarded
> by dg-require-effective-target fstack_protector).
> 
> OK for trunk?
> 
> Thanks,
> 
> Christophe.
> 2013-06-28  Christophe Lyon  <christophe.lyon@linaro.org>
> 
> * config/aarch64/aarch64.h (FRAME_GROWS_DOWNWARD): Define to 1.
> * config/aarch64/aarch64.c (aarch64_initial_elimination_offset):
> Add get_frame_size () when eliminating frame pointer.

In general, when the files changed are same as the name of the port,
it's ok to write:

  * aarch64.h (...): ...

For aarch64_initial_elimination_offset, I suggest "Update offset
calculations."

Otherwise OK.

R.

> 
> 
> aarch64-frame.txt
> 
> 
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index 527b00d..d8f2801 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -1943,7 +1943,7 @@ aarch64_save_or_restore_callee_save_registers (HOST_WIDE_INT offset,
>     Establish the stack frame by decreasing the stack pointer with a
>     properly calculated size and, if necessary, create a frame record
>     filled with the values of LR and previous frame pointer.  The
> -   current FP is also set up is it is in use.  */
> +   current FP is also set up if it is in use.  */
>  
>  void
>  aarch64_expand_prologue (void)
> @@ -4031,7 +4031,7 @@ aarch64_initial_elimination_offset (unsigned from, unsigned to)
>  	 return offset - crtl->outgoing_args_size;
>  
>         if (from == FRAME_POINTER_REGNUM)
> -	 return cfun->machine->frame.saved_regs_size;
> +	 return cfun->machine->frame.saved_regs_size + get_frame_size ();
>       }
>  
>     if (to == STACK_POINTER_REGNUM)
> @@ -4040,6 +4040,7 @@ aarch64_initial_elimination_offset (unsigned from, unsigned to)
>           {
>             HOST_WIDE_INT elim = crtl->outgoing_args_size
>                                + cfun->machine->frame.saved_regs_size
> +                              + get_frame_size ()
>                                - cfun->machine->frame.fp_lr_offset;
>             elim = AARCH64_ROUND_UP (elim, STACK_BOUNDARY / BITS_PER_UNIT);
>             return elim;
> diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
> index a08797b..5048258 100644
> --- a/gcc/config/aarch64/aarch64.h
> +++ b/gcc/config/aarch64/aarch64.h
> @@ -434,7 +434,7 @@ enum reg_class
>  #define INDEX_REG_CLASS	CORE_REGS
>  #define BASE_REG_CLASS  POINTER_REGS
>  
> -/* Register pairs used to eliminate unneeded registers that point intoi
> +/* Register pairs used to eliminate unneeded registers that point into
>     the stack frame.  */
>  #define ELIMINABLE_REGS							\
>  {									\
> @@ -475,7 +475,7 @@ extern enum aarch64_processor aarch64_tune;
>  /* Stack layout; function entry, exit and calling.  */
>  #define STACK_GROWS_DOWNWARD	1
>  
> -#define FRAME_GROWS_DOWNWARD	0
> +#define FRAME_GROWS_DOWNWARD	1
>  
>  #define STARTING_FRAME_OFFSET	0
>  
>