Re: [PATCH bpf-next V2] bpf: abstract loop unrolling pragmas in BPF selftests

[Yonghong Song <yonghong.song@linux.dev>]

On 2/8/24 12:36 PM, Jose E. Marchesi wrote:
> [Changes from V1:
> - Avoid conflict by rebasing with latest master.]
>
> Some BPF tests use loop unrolling compiler pragmas that are clang
> specific and not supported by GCC.  These pragmas, along with their
> GCC equivalences are:
>
>    #pragma clang loop unroll_count(N)
>    #pragma GCC unroll N
>
>    #pragma clang loop unroll(full)
>    #pragma GCC unroll 65534
>
>    #pragma clang loop unroll(disable)
>    #pragma GCC unroll 1
>
>    #pragma unroll [aka #pragma clang loop unroll(enable)]
>    There is no GCC equivalence to this pragma.  It enables unrolling on
>    loops that the compiler would not ordinarily unroll even with
>    -O2|-funroll-loops, but it is not equivalent to full unrolling
>    either.
>
> This patch adds a new header progs/bpf_compiler.h that defines the
> following macros, which correspond to each pair of compiler-specific
> pragmas above:
>
>    __pragma_loop_unroll_count(N)
>    __pragma_loop_unroll_full
>    __pragma_loop_no_unroll
>    __pragma_loop_unroll
>
> The selftests using loop unrolling pragmas are then changed to include
> the header and use these macros in place of the explicit pragmas.
>
> Tested in bpf-next master.
> No regressions.
>
> Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>
> Cc: Yonghong Song <yhs@meta.com>
> Cc: Eduard Zingerman <eddyz87@gmail.com>
> Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Cc: david.faust@oracle.com
> Cc: cupertino.miranda@oracle.com

Acked-by: Yonghong Song <yonghong.song@linux.dev>