[clang] [AMDGPU] Remove Code Object V3 (PR #67118)

[Tobias Burnus via cfe-commits]

tob2 wrote:

> V3 has been deprecated for a while as well, so it can safely be removed

We are using v3 for (better) backward compatibility with the older gfx803 / fiji cards (GCN GFX8 (Volcanic Islands (VI))) — thus, this commit on Monday broke our tester for gfx803 / fiji cards :-(

However, for newer cards (like GCN GFX9 (Vega) – or newer), we use v4, which works perfectly well.

https://github.com/llvm/llvm-project/pull/67118