Re: [PATCH v2] x86/hweight: Fix and improve __arch_hweight{32,64}() assembly

[Uros Bizjak]

On Wed, Mar 12, 2025 at 1:09 PM Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
>
> * Uros Bizjak <ubizjak@xxxxxxxxx> 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. This unconstrained scheduling might
> > cause objtool to print a "call without frame pointer save/setup"
> > warning. Current versions of compilers don't seem to trigger this
> > condition, but without this constraint there's nothing to prevent
> > the compiler from scheduling the insn in front of frame creation.
> >
> > b) Use asm_inline to instruct the compiler that the size of asm()
> > is the minimum size of one instruction, ignoring how many instructions
> > the compiler thinks it is. ALTERNATIVE macro that expands to several
> > pseudo directives causes instruction length estimate to count
> > more than 20 instructions.
> >
> > c) Use named operands in inline asm.
>
> I think this should be a 3-patch series. While it all modifies the same
> code, each change could introduce separate issues, so it's better to be
> individually bisectable IMO ...

Ok, will split and send separate series.

Thanks,
Uros.