Re: Alias code

["Michael P. Hayes" <michaelh@ongaonga.chch.cri.nz>]

Joern Rennecke writes:
 > > While on the alias code subject, EGCS could do with a mechanism so
 > > that a programmer can hint to the compiler that a memory reference is
 > > to a different address space, say an internal memory block.  The
 > > backend could then do a better scheduling job by knowing that the
 > > memory access is likely to be faster than normal and that it won't
 > > conflict with an external memory access.  Any ideas?
 > 
 > We'd need yet another field in the MEM to represent that.

Yes, but how would we inform the front-end to set this flag?  Ideally,
C needs another qualifer like fast or internal to say that a pointer
is likely to be referring to something in internal memory.  It
probably should be more general to deal with processors, in particular
DSPs, that have multiple address spaces that the compiler needs to be
aware of when generating fast code.  Does anyone know how the SHARC
port deals with this?

 > Well, if we have that, then the md file can describe the stuff to the
 > scheduler by claiming to use different function units depending on
 > the address space.

Yes, that's one aspect I was thinking of.  I was also hoping to use
the flag during RTL generation.

Michael.