Re: [PATCH v6 9/9] drm/amd/display: Mark dc_fixpt_from_fraction() noinline

[Huacai Chen]

Hi, Tiezhu,

On Tue, Dec 17, 2024 at 9:50 AM Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> wrote:
>
> When compiling with Clang on LoongArch, there exists the following objtool
> warning in drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.o:
>
>   dc_fixpt_recip() falls through to next function dc_fixpt_sinc()
>
> This is because dc_fixpt_from_fraction() is inlined in dc_fixpt_recip()
> by Clang, given dc_fixpt_from_fraction() is not a simple function, just
> mark it noinline to avoid the above issue.
I don't know whether drm maintainers can accept this, because it looks
like a workaround. Yes, uninline this function "solve" a problem and
seems reasonable in this case because the function is "not simple",
but from another point of view, you may hide a type of bug.


Huacai

>
> Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c b/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
> index 88d3f9d7dd55..b40c6a21460d 100644
> --- a/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
> +++ b/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
> @@ -68,7 +68,7 @@ static inline unsigned long long complete_integer_division_u64(
>  #define GET_FRACTIONAL_PART(x) \
>         (FRACTIONAL_PART_MASK & (x))
>
> -struct fixed31_32 dc_fixpt_from_fraction(long long numerator, long long denominator)
> +noinline struct fixed31_32 dc_fixpt_from_fraction(long long numerator, long long denominator)
>  {
>         struct fixed31_32 res;
>
> --
> 2.42.0
>