Richard Biener writes: > On Wed, Sep 30, 2015 at 11:23 AM, Mikael Pettersson > <mikpeli...@gmail.com> wrote: > > Does gcc allow backends to have a say in how pointers are represented > > (bits beyond the address), what happens in conversions between pointer > > types, and what happens in conversions between pointers and uintptr_t? > > > > The target in question has: > > - one pointer format and set of load/store instructions for pointers to > > int/long > > - another format and set of load/store instructions for pointers to char > > - pointers to short use a third format in general, but can use the int/long > > format IF you know which half of the word you're going to access > > > > What mechanisms, if any, are present in gcc to deal with this? > > Basically none. The only thing I could imagine you could use is have > the pointer > formats be different address-spaces. The target controls how to > convert pointers > from/to different address-spaces. I am not aware of specialities for > pointer-to-int > or int-to-pointer conversion though - IIRC they simply use > bit-identical conversions > (thus subregs if the modes differ). > > But who would design this kind of weird architecture and think he could get > away with that easily? > > Richard.
It's an old mainframe architecture, not a new design. A company produced clones up until a few years ago. They also maintained a private gcc port based initially on gcc-3.2 and eventually on gcc-4.3, but were unable to rebase on gcc-4.4. I have access to that port, and am trying to figure out if it can be reimplemented in some sane say. /Mikael
