Messages in this thread | | | Date | Sun, 14 Oct 2018 22:02:41 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86: Use assembly instruction mnemonics instead of .byte streams in arch_hweight.h |
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On Sun, Oct 14, 2018 at 09:15:00PM +0200, Uros Bizjak wrote: > The ChangeLog says "real INSTRUCTION mnemonics", e.g. POPCNTQ and POPCNTL.
Right, INSTRUCTION.
> The compiler will generate the register name with the correct implied > width (e.g. %rax for long, %eax for int), so the assembler will be > able to cross check if operands fit the instruction
The __arch_hweightXX functions already enforce the proper type and the inline asm() operands already place the arguments in the proper registers where the instruction encoding expects them.
So if you're going to relax this, then you could relax the inline asm operand specifications too. I say you "could" because then you need to fix arch/x86/lib/hweight.S too, which would be at least ugly. So I think we're stuck with %xDI/xAX and %xAX as operands, where 'x' is either 'r' or 'e'.
> And there will be a couple of ugly #defines less.
That's the only advantage of this change AFAICT. How about you reflect that in your commit message?
Thx.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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