[Bug middle-end/109484] [Wrong Code][inline-asm] output operands overlap with output

["570070308 at qq dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109484

--- Comment #5 from 。 <570070308 at qq dot com> ---
(In reply to Richard Biener from comment #3)
> (In reply to 。 from comment #2)
> > (In reply to Richard Biener from comment #1)
> > > but you clobber 'temp' early and fail to indicate that so GCC allocates the
> > > same register as part of the "+m" output.
> > 
> > The requirements you describe are not reflected in the documentation. The
> > document only says that `GCC assumpts that the assembler code consumes its
> > inputs before producing outputs`, and this code fits the assumption. First,
> > it reads the input from %1, then write the output to %0, then write the
> > output to %1. No outputs happend before inputs.
> 
> You first write to 'temp' and then read from it.  The wording applies to the
> assigned register / address, _not_ to the C variables mapped.
> 
> Note I'm not an expert here and I wonder if an output operand is the
> appropriate
> way to create a scratch register for arbitrary use.

The second instruction is $0, not %0.