[llvm-commits] [PATCH, RFC] Medium code model support for 64-bit PowerPC

[Ulrich Weigand]

Bill Schmidt <wschmidt at linux.vnet.ibm.com> wrote:

> Here's a new revision of the patch.  The changes are:
>
> (1) Add support for direct object file writing:
>  - New relocation types in ELF.h.
>  - New fixup kinds in PPCFixupKinds.h
>  - Handle new fixups in PPCMCCodeEmitter.cpp, PPCAsmBackend.cpp, and
> PPCELFObjectWriter.cpp.

I think this may be a bit overkill; I don't think you need new fixups
(I see you followed the existing precedent of fixup_ppc_toc16 and
fixup_ppc_toc16_ds, but I think those are already unnecessary).

The *fixup* type describes *how* a value is to be inserted into an
instruction; this is the same for the TOC variants.  The difference
is only which *value* is to be inserted, and that is (supposed to
be) already encoded in the symbol kind.

PPCELFObjectWriter::getRelocTypeInner is then supposed to consult
the pair of fixup type and symbol kind to choose the appropriate
relocation type.  So instead of adding something like:

+    case PPC::fixup_ppc_toc16_lo:
+      Type = ELF::R_PPC64_TOC16_LO;
+      break;

I think you should rather add a check of symbol kind under the
existing PPC::fixup_ppc_lo16 case.  (Similar to what I did for
TPREL16_LO.)

Bye,
Ulrich