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Re: extend.texi patch on how to specify clobbered inputs (was: Re: i386, asm and forbidden spilled registers...)
- To: Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>
- Subject: Re: extend.texi patch on how to specify clobbered inputs (was: Re: i386, asm and forbidden spilled registers...)
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Tue, 03 Nov 1998 00:56:13 -0700
- cc: egcs-patches at cygnus dot com, gcc-patches at gnu dot org, cato at df dot lth dot se, leitner at math dot fu-berlin dot de, vonbrand at sleipnir dot valparaiso dot cl
- Reply-To: law at cygnus dot com
> + It is @emph{not} valid to use a clobber description to describe that an
> + input operand is modified, but unused as output. It has to be specified
> + as an input and output operand anyway. Note that if there are only
> + unused output operands, you will then also need to specify
> + @code{volatile} for the @code{asm} construct, as described below.
> +
This applies to both inputs and outputs -- ie, you can not show a register
as an output and also have it in the clobber list either.
ie, a register mentioned explicitly in the clobber list must not overlap
with an input or output operand.
jeff