Re: [Xen-devel] x86 string/memory inline functions

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 24 May 2006, at 09:55, Jan Beulich wrote:

> 1) Why were the (questionable) inline versions from i386 Linux chosen 
> over just using the gcc intrinsics (as x86-64
> Linux does, except for a special case of memcpy())?
Intrinsics are a total pain. Sometimes the compiler inlines, sometimes 
it doesn't. Sometimes it emits the __builtin_foo symbol, sometime it 
emits foo. Sometime when the function __builtin_foo is defined in 
string.c it gets the name __builtin_foo, but sometimes it gets the name 
foo. Getting this to work for a range of compiler versions on i386 
(that's where I see the wide range of behaviours) would be hassle.
The best solution is just to remove the arch-specific definitions. None 
of the uses in Xen are performance critical.
> 2) Why were the memory clobbers removed without at least replacing 
> them with appropriate input constraints?
Maybe I was having a bad day. :-)

 -- Keir


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