[PATCH] D95121: [lld-macho][NFC] refactor relocation handling

[Greg McGary via Phabricator via llvm-commits]

gkm marked 2 inline comments as done.
gkm added a comment.

I also completed the `TODO(gkm): hoist into target-independent code driven by RelocAttrBits` refactors for `prepareSymbolRelocation()` and `resolveSymbolVA()`



================
Comment at: lld/MachO/Target.h:50-51
+  GOT = 1 << 11,       // Has a Global Offset Table slot
+  TLV = 1 << 12,       // Has a Thread-Local Variable slot
+  TLS = 1 << 13,       // Can reside in Thread-Local Storage
+  MORPH = 1 << 14,     // morph instruction: load into add
----------------
int3 wrote:
> gkm wrote:
> > int3 wrote:
> > > I think ld64 (and other bits of macOS source) use "TLV" in place of "TLS". Pointers to TLVs are abbreviated as `TLVP`s.
> > That's a real distinction, and apparently needs more commentary to avoid confusion:
> > TLV = //Thread-Local Variable// and pertains to the datum and its symbol.
> > TLS = //Thread-Local Storage// and pertains to the section that contains the TLVs.
> I understood the distinction... I'm saying that `TLVP` seems like a more appropriate name for the former and `TLV` for the latter. In particular, in the `SectionType` enum, we have
> 
> ```
>   /// S_THREAD_LOCAL_VARIABLES - Section with thread local variable
>   /// structure data.
>   S_THREAD_LOCAL_VARIABLES = 0x13u,
>   /// S_THREAD_LOCAL_VARIABLE_POINTERS - Section with pointers to thread
>   /// local structures.
>   S_THREAD_LOCAL_VARIABLE_POINTERS = 0x14u,
> ```
> 
> Based on the above, it seems fitting to me that a reloc which can be present in a S_THREAD_LOCAL_VARIABLES section has attribute TLV. And similarly TLVP seems like a fitting name for a reloc which can point to an address in a S_THREAD_LOCAL_VARIABLES section.
> 
> I'm aware that "TLS" is commonly used in the sense that you are describing, but from what I can tell neither ld64 nor dyld use that abbreviation, so it would be nice to hew to that.
Very good. I realized we only need one bit, which I named `TLV`. Thread-local Variable Pointer relocs are `TLV|LOAD`, and Thread-local Variable relocs are `TLV` (no `LOAD`).

BTW, `LOAD` is a new name for what I had been calling `MORPH`, and then `RELAX`.


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  https://reviews.llvm.org/D95121/new/

https://reviews.llvm.org/D95121