[all-commits] [llvm/llvm-project] 7daa65: Reland "[NVPTX] Use .common linkage for common glo...

[Alex MacLean via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7daa65a088c00891662d5e7e162e5f8f3283f799
      https://github.com/llvm/llvm-project/commit/7daa65a088c00891662d5e7e162e5f8f3283f799
  Author: Alex MacLean <amaclean at nvidia.com>
  Date:   2024-03-29 (Fri, 29 Mar 2024)

  Changed paths:
    M llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
    A llvm/test/CodeGen/NVPTX/common-linkage.ll
    M llvm/test/CodeGen/NVPTX/weak-global.ll

  Log Message:
  -----------
  Reland "[NVPTX] Use .common linkage for common globals" (#86824)

Switch from `.weak` to `.common` linkage for common global variables
where possible. The `.common` linkage is described in
[PTX ISA 11.6.4. Linking Directives: .common]
(https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#linking-directives-common)
> Declares identifier to be globally visible but “common”.
>
>Common symbols are similar to globally visible symbols. However
multiple object files may declare the same common symbol and they may
have different types and sizes and references to a symbol get resolved
against a common symbol with the largest size.
>
>Only one object file can initialize a common symbol and that must have
the largest size among all other definitions of that common symbol from
different object files.
>
>.common linking directive can be used only on variables with .global
storage. It cannot be used on function symbols or on symbols with opaque
type.

I've updated the logic and tests to only use `.common` for PTX 5.0 or
greater and verified that the new tests now pass with `ptxas`.



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