Re: egcs 1.0.1 miscompiles Linux 2.0.33

Christof Petig (
Thu, 05 Mar 1998 10:17:42 +0100

Jeffrey A Law wrote:

> In message <>you write:
> No, I don't use x86 asms a lot. But I've had the "pleasure" of
> working with asms on various machines and developing gcc for about
> 9 years now. So I have more than a clue about how things are
> supposed to work :-)

This gives me a release. Really.

> As folks have stated, the proper way to do this is to set up matching
> input/output operands with the output as an earlyclobber. The manual
> needs updating in this regard since it is ambigious.
> Any asm which sets up a case where a clobber must match an input
> is wrong. Plain and simple, it is wrong.

Could you please explain the syntax of an earlyclobber (I never heard of it).
I would undergo the task of patching Linux-Kernel's asms, since I'd like to
stop the debate about an EGCS/Kernel mismatch. EGCS is a valuable project and
compiling a kernel should not delay using it.

> And finally, the earlyclobber on the output prevents the compiler
> from associating any unrelated input with the given output.
> This mechanism is designed to do exactly what you want it to do
> modulo any bugs.

> The need for the mechanism is obvious, the mechanism currently used
> by Linux is wrong.
> jeff


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