[clang] [lld] [llvm] [Windows] Add support for emitting PGO/LTO magic strings in the Windows PE debug directory (PR #114260)

[Wei Xiao via cfe-commits]

williamweixiao wrote:

> @mikolaj-pirog Are you planning on getting back to this? I find it nevertheless interesting, as long as we can bind it with PGO information from LLVM & properly generate the corresponding `IMAGE_DEBUG_TYPE_POGO` entry in the file. I am seeing this: https://github.com/CasualX/pelite/blob/e9d2dfaadaa5d225d220e703f757930f70c7b8a2/src/wrap/debug.rs#L198 documents the format for that entry. There might be other places accross github (I just looked up `IMAGE_DEBUG_TYPE_POGO`)

@aganea since @mikolaj-pirog is busy with other stuffs right now and I've synced with him offline that I will follow up on this PR. I've prepared an updated draft version (https://github.com/llvm/llvm-project/pull/173514) to support coffgrp. Could you please take a look at the draft? If the direction is ok, then I will update the base to the latest LLVM trunk.

https://github.com/llvm/llvm-project/pull/114260