[MLton] -mtune=opteron considered harmful

[Matthew Fluet]

On Mon, 13 Aug 2007, Matthew Fluet wrote:
> On Mon, 13 Aug 2007, Matthew Fluet wrote:
>>  On Tue, 14 Aug 2007, Florian Weimer wrote:
>> >   On Debian unstable at least, the C parts of MLton are compiled with
>> >   -mtune=opteron.  With recent GCCs (4.1 in some distros, and 4.2
>> >   mainline), this overrides the default of -mtune=generic, and produces
>> >   code that doesn't run very well on Netburst machines.  (The impact on
>> >   the Core architecture should be less significant, if measurable at
>> >   all.)
>>
>>  Fair enough; I'm not sure it was doing anything particularly useful.
>
> By which, I mean that (by default) it is only used when compiling the 
> runtime.  (It would also be used when compiling the programs with the 
> C-codegen, but GCC 4.1.2 and 4.2.1 have bugs that cause gcc ICEs with the 
> C-codegen code.)

BTW, I've only observed these ICEs with the amd64 architecture; it doesn't 
seem to be present with x86.  In any case, on both of these platforms, 
we have the native codegens.  I've no idea about powerpc or sparc.