SHA1.hs woes, was Version control systems

[Duncan Coutts]

On Tue, 2008-08-19 at 23:55 +1000, Ben Lippmeier wrote:
> On 19/08/2008, at 8:57 PM, Ian Lynagh wrote:
> 
> > On Mon, Aug 18, 2008 at 09:20:54PM +1000, Ben Lippmeier wrote:
> >>
> >> Ian: Did this problem result in Intel CC / GCC register allocator
> >> freakouts?
> >
> > Have you got me confused with someone else? I don't think I've ever  
> > used
> > Intel CC.
> >
> 
> Sorry, I couldn't find the rest of the preceding message. Someone  
> wrote that they had to turn down cc flags to get SHA1.hs to compile on  
> IA64.

Yep.

> What C compiler was being used, and what were the symptoms?

GCC.

As I recall the symptoms were that gcc used more than 32 registers and
then the mangler balked. The reason is that a registerised ia64 build
expects to only use the first 32 registers but does not take any
precautions to make sure that this is the case. It just relies on the
fact that most code coming out of the ghc backend cannot make use of
more than a handful of registers. If gcc does actually use more then the
mangler catches this. We tried some flags to make gcc restrict itself to
a subset of the registers but could not get it to obey.

Duncan