[llvm-branch-commits] [LowerAllowCheck] Add llvm.allow.sanitize.* intrinsics (PR #172029)

[Marco Elver via llvm-branch-commits]

melver wrote:

> > LowerAllowCheckPass is now "required" to run on functions with optnone to ensure correct lowering at O0.
> 
> Please do not add yet another new pass that scans all instructions at O0 in order to lower a rarely used intrinsic. Can this be integrated with an existing pass that does this instead, like PreISelIntrinsicLowering for example?

This pass is not added to the default pass pipelines built by the PassBuilder. It's inserted by Clang, only when required. The follow-up patch changes it to run when sanitizers are enabled.

The problem was that even when Clang inserted it, it was ignored at O0.

https://github.com/llvm/llvm-project/pull/172029