[llvm] [SLP] Make getSameOpcode support interchangeable instructions. (PR #127450)

[Han-Kuan Chen via llvm-commits]

HanKuanChen wrote:

> Thanks @mstorsjo for reverting!
> 
> > Cannot reproduce the error. My SHA-1 is [71a0cfd](https://github.com/llvm/llvm-project/commit/71a0cfd93263552ddc0bfd2ea7b0abe9a578f87e). Do you miss anything?
> 
> Very certain it's this commit. Did you enable asserts in your local build? Hopefully the other repros can increase the chance of reproducability for you.

The error you encountered is different from the others. I would appreciate it if you could provide the steps to reproduce it. Here is my cmake command
```
cmake -DCMAKE_C_COMPILER=clang \
      -DCMAKE_CXX_COMPILER=clang++ \
      -DCMAKE_BUILD_TYPE=Debug \
      -DLLVM_APPEND_VC_REV=OFF \
      -DLLVM_ENABLE_ASSERTIONS=ON \
      -DLLVM_ENABLE_PROJECTS="clang;lld" \
      -DLLVM_ENABLE_RUNTIMES=all \
      -DLLVM_USE_LINKER=lld \
      -G Ninja ../llvm
```

https://github.com/llvm/llvm-project/pull/127450