Re: [x86 testsuite] preserve full register across main

[Uros Bizjak <ubizjak@gmail.com>]

On Friday, August 23, 2019, Alexandre Oliva <oliva@adacore.com> wrote:
> This test uses a call-saved register as a global variable.  It
> attempts to preserve its value across main, but only the lower int
> part is preserved, which is not good enough for x86_64, when the
> runtime that calls main() happens to hold something in the chosen
> register that is not a zero-extension from the 32-bit value, and
> rightfully expects the full register to remain unchanged when main()
> returns.
>
> Tested on x86_64-linux-gnu, both -m64 and -m32.  Ok to install?
>
>
> for  gcc/testsuite/ChangeLog
>
>         * gcc.target/i386/20020616-1.c: Preserve full register across
>         main.
> ---
>  gcc/testsuite/gcc.target/i386/20020616-1.c |   14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/testsuite/gcc.target/i386/20020616-1.c
b/gcc/testsuite/gcc.target/i386/20020616-1.c
> index 5641826b4837..3b8cf8e41783 100644
> --- a/gcc/testsuite/gcc.target/i386/20020616-1.c
> +++ b/gcc/testsuite/gcc.target/i386/20020616-1.c
> @@ -2,12 +2,16 @@
>  /* { dg-do run } */
>  /* { dg-options "-O2" } */
>
> +/* We need this type to be as wide as the register chosen below, so
> +   that, when we preserve it across main, we preserve all of it.  */
> +typedef long reg_type;

Can __attribute__ ((mode (__word__))) be used here?

Otherwise OK.

Thanks,
Uros.

>  #if !__PIC__
> -register int k asm("%ebx");
> +register reg_type k asm("%ebx");
>  #elif __amd64
> -register int k asm("%r12");
> +register reg_type k asm("%r12");
>  #else
> -register int k asm("%esi");
> +register reg_type k asm("%esi");
>  #endif
>
>  void __attribute__((noinline))
> @@ -18,7 +22,7 @@ foo()
>
>  void test()
>  {
> -  int i;
> +  reg_type i;
>    for (i = 0; i < 10; i += k)
>      {
>        k = 0;
> @@ -28,7 +32,7 @@ void test()
>
>  int main()
>  {
> -  int old = k;
> +  reg_type old = k;
>    test();
>    k = old;
>    return 0;
>
> --
> Alexandre Oliva, freedom fighter  he/him   https://FSFLA.org/blogs/lxo
> Be the change, be Free!                 FSF Latin America board member
> GNU Toolchain Engineer                        Free Software Evangelist
> Hay que enGNUrecerse, pero sin perder la terGNUra jamás - Che GNUevara
>