Re: [PATCH] x86/hweight: Fix and improve __arch_hweight{32,64}() assembly

[Uros Bizjak]

On Mon, Mar 10, 2025 at 9:12 PM Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> On Mon, Mar 10, 2025 at 09:08:04PM +0100, Uros Bizjak wrote:
> > a) Use ASM_CALL_CONSTRAINT to prevent inline asm that includes call
> > instruction from being scheduled before the frame pointer gets set
> > up by the containing function, causing objtool to print a "call
> > without frame pointer save/setup" warning.
>
> The other two are ok but this is new. How do you trigger this? I've never seen
> it in my randconfig builds...

It is not triggered now, but without this constraint, nothing prevents
the compiler from scheduling the insn in front of frame creation.

Uros.