[llvm] [CodeGenPrepare] Return false in AddressingModeMatcher::matchOperationAddr if zext has nneg flag (PR #72098)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

This isn't the right fix. Instead, there should be a dropPoisonGeneratingFlags() call at the point where the zext operand is updated. The code is pretty convoluted, but I think this happens inside this method: https://github.com/llvm/llvm-project/blob/b0d36410b2c847598e9965e00af16919a92a79d2/llvm/lib/CodeGen/CodeGenPrepare.cpp#L4529

Also, this PR is missing a test.

https://github.com/llvm/llvm-project/pull/72098