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From: David Brown <david.brown@hesbynett.no>
Subject: Re: Odd error with the "X" inline assembly constraint
Date: Mon, 8 Jan 2024 19:39:39 +0100
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On 07/01/2024 19:32, Segher Boessenkool wrote:
> On Sun, Jan 07, 2024 at 06:04:23PM +0800, LIU Hao wrote:
>> 在 2024/1/6 2:46, Segher Boessenkool 写道:
>>> The C constraint means "Any operand whatsoever is allowed."  Here you
>>> are saying to use it both as input and as output, and GCC does not know
>>> how to reload wherever it chose to put it.
>>
>> Would you mind elaborating a bit more? On x86 and x86-64 it's almost always
>> the case that an expression can be used as either a source or a destination.
> 
> This is just GCC internals.  The compiler will never look at the
> template string in an asm at all, anyway.
> 
> I don't know why exactly you get the error.  Make a compilable
> reproducer, file a bug (<https://gcc.gnu.org/bugs.html>), it sounds like
> something we can improve :-)
> 

I've filed it :

<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113280>

I don't know if this is something that the developer will want to spend 
much time on, but it might appeal to someone's curiosity!

David