Re: Clang and X86-EFlags (was Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning)

[Linus Torvalds]

On Tue, Apr 24, 2018 at 6:28 AM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
>
> $ objdump -S clang-eflag.o
>
> Does this now look good?

Looks fine to me. The instruction choice is still pretty odd:

  1a:   f6 c3 ff                test   $0xff,%bl
  1d:   74 02                   je     21 <bar+0x21>

that "test   $0xff,%bl" is a rather odd way of testing the byte for zero, since

  1a:   84 db                test   %bl,%bl
  1c:   74 02                   je     20 <bar+0x20>

would have been a byte shorter and is the canonical way on x86 to test
a register against zero.

But that's just a "looks odd to somebody who is used to x86 asm", not
a bug or anything really noticeable.

                  Linus