[PATCH] D64827: [Xtensa 2/10] Add Xtensa ELF definitions.

Fri Aug 19 11:34:22 PDT 2022

saugustine accepted this revision.
saugustine added a comment.

OK with one minor change.

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Comment at: llvm/include/llvm/BinaryFormat/ELFRelocs/Xtensa.def:11
+ELF_RELOC (R_XTENSA_RELATIVE, 5)
+ELF_RELOC (R_XTENSA_PLT, 6)
+ELF_RELOC (R_XTENSA_OP0, 8)
----------------
andreisfr wrote:
> jhenderson wrote:
> > andreisfr wrote:
> > > appcs wrote:
> > > > Just making sure a '7' RELOC is not missing.
> > > It is missing also in binutils (binutils/include/elf/xtensa.h). So I left it as is.
> > Is there an xtensa specification anywhere?
> There is some description of the Xtensa relocations in GNU Binutils ( in binutils/bfd/doc/bfd.info file and source code). As I understand most of ELF relocations for other architectures in LLVM are imported from binutils, so the same approach was used for Xtensa.
To the best of my knowledge Xtensa does not have a formal elf specification. They definitely didn't a in the years I worked there. The binutils implementation governed. 

My recollection is very hazy almost twenty years later, but I believe 7 was used in some experiments during the original port and we later determined it wasn't useful. But by the time we removed it, the other assignments had already been made.

I think instead of leaving it unused and blank, we should use something like:

ELF_RELOC(R_XTENSA_RESERVED_7,          7)

which will better show that this isn't a mistake. and probably what we should have done originally.

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https://reviews.llvm.org/D64827