[llvm-commits] [PATCH, RFC] 64-bit PowerPC ELF support for Initial Exec TLS model

[Hal Finkel]

----- Original Message -----
> From: "Hal Finkel" <hfinkel at anl.gov>
> To: "Bill Schmidt" <wschmidt at linux.vnet.ibm.com>
> Cc: llvm-commits at cs.uiuc.edu
> Sent: Monday, December 3, 2012 2:42:25 PM
> Subject: Re: [llvm-commits] [PATCH,	RFC] 64-bit PowerPC ELF support for Initial Exec TLS model
> 
> Bill,
> 
> Thanks for working on this!
> 
> One quick comment: please add triples to the test cases (otherwise
> the Darwin ppc builtbots may complain).

Ignore this; they're there and I did not see them ;)

 -Hal

> 
>  -Hal
> 
> ----- Original Message -----
> > From: "Bill Schmidt" <wschmidt at linux.vnet.ibm.com>
> > To: llvm-commits at cs.uiuc.edu
> > Sent: Monday, December 3, 2012 2:09:05 PM
> > Subject: [llvm-commits] [PATCH,	RFC] 64-bit PowerPC ELF support for
> > Initial Exec TLS model
> > 
> > Here's some incremental progress on thread-local storage.  I've
> > verified
> > it introduces no regressions.  Thought I'd open it up to comments
> > before
> > committing in case there's anything obvious I've missed.
> > 
> > I've had one comment that the lib/Target/PowerPC/PPC.h changes
> > could
> > be
> > a separate patch.  I'm not sure if that's useful, since there isn't
> > any
> > new testable function by doing that.  But I don't feel strongly
> > either
> > way.
> > 
> > Thanks,
> > Bill
> > --
> > Bill Schmidt, Ph.D.
> > IBM Advance Toolchain for PowerLinux
> > IBM Linux Technology Center
> > wschmidt at linux.vnet.ibm.com
> > wschmidt at us.ibm.com
> > 
> > --------------------------------------------------------------------------
> > This patch introduces initial-exec model support for thread-local
> > storage
> > on 64-bit PowerPC ELF.
> > 
> > The patch includes code to handle external assembly and MC output
> > with the
> > integrated assembler.  It intentionally does not support the "old"
> > JIT.
> > 
> > For the initial-exec TLS model, the ABI requires the following to
> > calculate
> > the address of external thread-local variable x:
> > 
> >  Code sequence            Relocation                  Symbol
> >   ld 9,x at got@tprel(2)      R_PPC64_GOT_TPREL16_DS      x
> >   add 9,9,x at tls            R_PPC64_TLS                 x
> > 
> > The register 9 is arbitrary here.  The linker will replace
> > x at got@tprel
> > with the offset relative to the thread pointer to the generated GOT
> > entry for symbol x.  It will replace x at tls with the thread-pointer
> > register (13).
> > 
> > The two test cases verify correct assembly output and relocation
> > output
> > as just described.
> > 
> > PowerPC-specific selection node variants are added for the two
> > instructions above:  LD_GOT_TPREL and ADD_TLS.  These are inserted
> > when an initial-exec global variable is encountered by
> > PPCTargetLowering::LowerGlobalTLSAddress(), and later lowered to
> > machine instructions LDgotTPREL and ADD8TLS.  LDgotTPREL is a
> > pseudo
> > that uses the same LDrs support added for medium code model's
> > LDtocL,
> > with a different relocation type.
> > 
> > The rest of the processing is (relatively) straightforward.
> > 
> > 
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> > 
> 
> --
> Hal Finkel
> Postdoctoral Appointee
> Leadership Computing Facility
> Argonne National Laboratory
> 

-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory