Re: [PATCH] rs6000/test: Fix bswap64-4.c with has_arch_ppc64 [PR106680]

[Segher Boessenkool <segher@kernel.crashing.org>]

On Wed, Aug 31, 2022 at 05:33:28PM +0800, Kewen.Lin wrote:
> Test case bswap64-4.c suffers the issue as its comments:
> 
> /* On some versions of dejagnu this test will fail when
>    biarch testing with RUNTESTFLAGS="--target_board=unix
>    '{-m64,-m32}'" due to -m32 being added on the command
>    line after the dg-options -mpowerpc64.
>    common/config/rs6000/rs6000-common.c:
>    rs6000_handle_option disables -mpowerpc64 for -m32.  */
> 
> As tested, on test machine with dejaGnu 1.6.2, the compilation
> option order looks like: -m32 ... -mpowerpc64, option
> -mpowerpc64 still takes effect;  While on test machine with
> dejaGnu 1.5.1, the option order looks like: -mpowerpc64 ... -m32,
> option -mpowerpc64 is disabled by -m32, then the case fails.

*Should* -mpowerpc64  be disabled by -m32?  Should *any* explicit
command line flag ever be disabled like that?  (Not talking about things
like -m32 -m64, this should be supported for convenience).

-mpowerpc64 -m32 should always mean the same as -m32 -mpowerpc64, that's
the principle of least surprise.

Where then dg-options is placed does not matter in this testcase, both
-m32 -mno-powerpc64 and -m32 -mpowerpc64 are ilp32.


Segher