Re: [PATCH] sim: riscv: Make stack 16-byte aligned

[Andrew Burgess <aburgess@redhat.com>]

Bernd Edlinger <bernd.edlinger@hotmail.de> writes:

> Various gcc test cases fail due to the stack
> alignment of 16 bytes is expected by gcc,

And indeed by the RISC-V ABI specification I believe.

> causing issues mostly with vararg functinos;

Typo: functions.

> e.g.
>
> FAIL: gcc.c-torture/execute/nest-align-1.c   -O0  execution test
> FAIL: gcc.c-torture/execute/nest-stdar-1.c   -O0  execution test
> FAIL: gcc.c-torture/execute/va-arg-12.c   -O0  execution test
> FAIL: gcc.c-torture/execute/va-arg-15.c   -O0  execution test
> FAIL: gcc.c-torture/execute/va-arg-16.c   -O0  execution test
> FAIL: gcc.c-torture/execute/va-arg-17.c   -O0  execution test
> FAIL: gcc.c-torture/execute/va-arg-20.c   -O0  execution test
> FAIL: gcc.c-torture/execute/va-arg-26.c   -O0  execution test
> ...
> ---
>  sim/riscv/sim-main.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/sim/riscv/sim-main.c b/sim/riscv/sim-main.c
> index 4e3672505c6..0876d455570 100644
> --- a/sim/riscv/sim-main.c
> +++ b/sim/riscv/sim-main.c
> @@ -1586,6 +1586,8 @@ initialize_env (SIM_DESC sd, const char * const *argv, const char * const *env)
>    sp = sp_flat - ((argc + 1 + envc + 1) * sizeof (address_word));
>    /* Then the argc.  */
>    sp -= sizeof (unsigned_word);
> +  /* Align to 16 bytes.  */
> +  sp &= ~(address_word)15;

I think you should use 'align_down' from common/sim-bits.h, as:

  /* Align to 16 bytes.  */
  sp = align_down (sp, 15);

Assuming that works then:

Approved-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>  
>    /* Set up the regs the libgloss crt0 expects.  */
>    riscv_cpu->a0 = argc;
> -- 
> 2.25.1