[PATCH] D156497: [BPF] Emit UNDEF rather than constant 0

[Yonghong Song via Phabricator via llvm-commits]

yonghong-song added a comment.

So if I understand correctly, BPF backend can handle clang frontend generated IR properly and issue proper warning. But with rust frontend, the IR is a little bit different and BPF backend will behave differently and allow to generate illegal code. Is this right? The bpf-unsupported-emit.c is exactly the case to demonstrate that rust frontend may generate different IR and the BPF backend will generate incorrect code. Is my understanding correct?

Regarding to diag from constant 0 to undef, I am not 100% confident that this will solve all the problems. What if now r0 is undef but later continued compilation generates an assignment to r0? So we should solve the problem to ensure for buggy code the compilation fail rather succeed.


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https://reviews.llvm.org/D156497