[PATCH] D142229: [docs] add early Arm arch support improvements to release notes

Mon Jan 23 07:11:44 PST 2023

peter.smith added a comment.

I think this is pretty close. I think we shouldn't claim full support for Armv4 as we don't support the R_ARMV4BX relocation yet.

================
Comment at: llvm/docs/ReleaseNotes.rst:133
   architecture versions so their presence was misleading.
+* Added full LLD support for Armv4 and Armv4T by adding support for Armv4 and
+  Armv4T thunks. LLD will no longer generate BX instructions for Armv4 or BLX
----------------
Sadly I think we'll need to drop full support for Armv4 as we are missing support for the R_ARM_V4BX relocation (https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/ARM.cpp#L166) . This isn't important for clang as it uses mov pc,lr when compiling for -march=armv4, but it is possible that some GNU input objects will have bx lr along with a R_ARM_V4BX relocation.

I suggest
* Added Armv4 and Armv4T compatible thunks. LLD will no longer generate BX instructions for Armv4 or BLX instructions for either Armv4 or Armv4T. Armv4T is now fully supported.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142229/new/

https://reviews.llvm.org/D142229