[clang] [llvm] [BPF] Do atomic_fetch_*() pattern matching with memory ordering (PR #107343)

[via cfe-commits]

yonghong-song wrote:

> Looks like the new test case is failing on SystemZ: https://lab.llvm.org/buildbot/#/builders/42/builds/1192
> 
> ```
> struct.error: unpack_from requires a buffer of at least 402653196 bytes for unpacking 12 bytes at offset 402653184 (actual buffer size is 479)
> ```
> 
> At first glance, this might be an endian problem (SystemZ is big-endian; 402653196 is 0x1800000c).

Thanks for reporting! The test explicitly specified little endian like below:
```
; RUN: llc -march=bpfel -mcpu=v3 -filetype=obj -o %t1 %s
; RUN: llvm-objcopy --dump-section='.BTF'=%t2 %t1
; RUN: %python %p/print_btf.py %t2 | FileCheck -check-prefixes=CHECK %s
```
Let me investigate what is the problem here.

https://github.com/llvm/llvm-project/pull/107343