[all-commits] [llvm/llvm-project] 1bae02: [Cuda] Use fallback method to mangle externalized ...

[Joseph Huber via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1bae02b77335eb1a01d9a0bb36c2b2a29dfdd5d9
      https://github.com/llvm/llvm-project/commit/1bae02b77335eb1a01d9a0bb36c2b2a29dfdd5d9
  Author: Joseph Huber <jhuber6 at vols.utk.edu>
  Date:   2022-05-26 (Thu, 26 May 2022)

  Changed paths:
    M clang/lib/CodeGen/CGCUDANV.cpp
    M clang/lib/CodeGen/CodeGenModule.cpp
    M clang/lib/CodeGen/CodeGenModule.h
    M clang/test/CodeGenCUDA/device-fun-linkage.cu
    M clang/test/CodeGenCUDA/static-device-var-rdc.cu

  Log Message:
  -----------
  [Cuda] Use fallback method to mangle externalized decls if no CUID given

CUDA requires that static variables be visible to the host when
offloading. However, The standard semantics of a stiatc variable dictate
that it should not be visible outside of the current file. In order to
access it from the host we need to perform "externalization" on the
static variable on the device. This requires generating a semi-unique
name that can be affixed to the variable as to not cause linker errors.

This is currently done using the CUID functionality, an MD5 hash value
set up by the clang driver. This allows us to achieve is mostly unique
ID that is unique even between multiple compilations of the same file.
However, this is not always availible. Instead, this patch uses the
unique ID from the file to generate a unique symbol name. This will
create a unique name that is consistent between the host and device side
compilations without requiring the CUID to be entered by the driver. The
one downside to this is that we are no longer stable under multiple
compilations of the same file. However, this is a very niche use-case
and is not supported by Nvidia's CUDA compiler so it likely to be good
enough.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D125904