[LLVMdev] Register Class assignment for integer and pointer types

[杨勇勇]

David, thanks for your immediate response.

Since iPTR is a reserved type for tablegen internal use, can you make a
further explanation?

On the other hand, it can be simply treated as a register class assignment
problem during register allocation.
Assume both pointer and integet have a 32 bit width. backend handles it
just as to i32. When it performs register allocation, it can retrieve from
target constraint information about which register class is valid for a
operand, and this is determined by which instruction consumes the operand.

So is there a convienient way to constrain register class assignment, like
a tablegen interface or something else?

Regards.

2013/6/21 David Chisnall <David.Chisnall at cl.cam.ac.uk>

> We also have this problem, and have added iPTR types to the back end.  Our
> pointers are actually fat pointers, so this also requires tweaking some
> optimisations (for example, things like to turn GEPs with 64-bit offsets
> into pointer-sized offsets, but our pointers are larger than any integer
> type that we support...).  Most of the changes are a bit ugly, and I'm
> loath to upstream them without an in-tree target that has these
> requirements, or they will be hard for anyone else to keep working.
>
> David
>
> On 21 Jun 2013, at 06:00, 杨勇勇 <triple.yang at gmail.com> wrote:
>
> > llvm code generator lowers both integer and pointer types into ixx(say,
> i16, i32, i64, ...). This make senses for some optimizations.
> >
> > However, integer registers and pointer registers is expilicitly
> distinguished from each other for some architectures, like TriCore,
> Blackfin, and our lab prototype dsp, which accelerates address computation
> and memory access.
> >
> > I have already read this mail thread:
> http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-May/022142.html , and I
> am wondering how is the progress about it.
> >
> > Thanks.
> >
> > --
> > 杨勇勇 (Yang Yong-Yong)
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>


-- 
杨勇勇 (Yang Yong-Yong)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130623/bc5f3a08/attachment.html>