[Lldb-commits] [PATCH] D117928: [lldb] Disable tests for x86 that uses write command on XMM registers

Luís Ferreira via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Fri Jan 21 16:34:42 PST 2022

ljmf00 added a comment.

In D117928#3262710 <https://reviews.llvm.org/D117928#3262710>, @jingham wrote:

> I guess we're just all confused that you are mentioning GDB at all, and the only thing I could think of is gdbserver, since that's the only way anything GDB could get mixed with anything LLDB...

Ok, I will try to give some context. I can be wrong/confused and this can be unrelated to GDB and a coincidence with my observable behaviour, but running LLDB with default settings, `register write` command triggers the following function https://github.com/llvm/llvm-project/blob/main/lldb/source/Plugins/Process/gdb-remote/GDBRemoteRegisterContext.cpp#L296 .

Interestingly, I just did a test right now: removed GDB from my machine and did a clean build. That function (`GDBRemoteRegisterContext::WriteRegister`) still triggers when `register write`. I'm a bit confused now on why this is triggered. Maybe there is a fallback system? I don't have any guidance on this whatsoever, so my view on how those plugins work can be wrong. Would be cool to have a brief explanation about the //pipeline// of `RegisterContext` and how it interacts with `GDBRemoteRegisterContext` to be in sync.

Can be confusing to add a link to the GDB bug tracker, but one thing I can be sure of is that this is dependent on the CPU and by the observed behaviour, the presence of AVX or some other extension introduced on x86_64-v2 related to XMM registers (can't think of another one other than SSE). I can also describe my testing environment and give the libvirt/qemu parameters I added to virtualize the CPU flags, if needed, but the CPU configuration is similar to the models I described. I ran LLDB on a clean archiso live installation.

In D117928#3262762 <https://reviews.llvm.org/D117928#3262762>, @mgorny wrote:

> I'm sorry but I don't understand what you're talking about. Could you explain how are you running tests? Is there some way we can reproduce the problem?

You can see a build log I posted on discourse: https://ipfs.io/ipfs/bafybeidsf745d4qxrzhbbir4h23ov4rppvo2uke7qh75oj6lfoi6zkcyre/

  rG LLVM Github Monorepo



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