[WinEH] Missing register reload in catch funclet

[kalle-llvm]

This code:

https://godbolt.org/z/xxoY4zhTG

is miscompiled by clang, a register is not reloaded in the catch-funclet so 'this' becomes garbage inside the catch. I'm using 15.0.7 and I have tried different versions on godbolt. Starting with 8.0.0 they give essentially the same code. (Versions before this give correct code, but that may just be a fluke, this bug was hard to reproduce...)

Karl-Johan Johnsson

repro.cpp.txt

[llvmbot]

@llvm/issue-subscribers-clang-codegen

[kalle-llvm]

BTW, I think this is probably a backend bug, the IR that comes from clang looks correct as far as I can see.

repro.ll.txt

[kalle-llvm]

It seems that the bug is caused by MachineLICM hoisting the register reload out of the loop (and so out of the catch).

I guess a conservative fix would be to have MachineLICM skip loops that contain catchswitch blocks.