wallace marked 16 inline comments as done.
wallace added inline comments.
================
Comment at: lldb/source/Plugins/Trace/intel-pt/IntelPTDecoder.cpp:188
+ if (int error = pt_image_set_callback(image, ReadProcessMemory, &process))
+ return CreateLibiptError(error);
+
----------------
labath wrote:
> It looks like this can only fail if the image argument is null (which can
> only happen if the decoder is null, which is checked). An assert would be
> enough for that. (For a proper error handling you should have also freed the
> decoder object on the error path, which is how i came to thing about this).
good catch!
================
Comment at: lldb/source/Plugins/Trace/intel-pt/TraceIntelPT.cpp:98
+ int delta = direction == TraceDirection::Forwards ? -1 : 1;
+ for (uint64_t i = position; i < instructions.size() && i >= 0; i += delta)
+ if (!callback(i, instructions[i].GetLoadAddress()))
----------------
clayborg wrote:
> labath wrote:
> > `i>=0` is always true. You'll have to do this trick with signed numbers
> > (ssize_t?)
> Yes, switch to ssize_t, your delta is already signed. Also switch "delta" to
> ssize_t as well.
TIL!
================
Comment at: lldb/source/Plugins/Trace/intel-pt/TraceIntelPT.cpp:109
+ else {
+ consumeError(decoded_thread.takeError());
+ return 0;
----------------
labath wrote:
> I'm having doubts about this "I have an thread but was not able to decode
> _anything_ about it" state is worth it. Having many different ways to report
> errors just increases the chance of something going wrong, and in
> `TraverseInstructions` you're already treating this state as a
> pseudo-instruction.
>
> Maybe that representation should be used all the way down? Or (and this may
> be even better) we avoid creating such Threads in the first place (print an
> error/warning when the target is created).
> Maybe that representation should be used all the way down?
I'll follow that path. This will create consistency through the code
> Or (and this may be even better) we avoid creating such Threads in the first
> place (print an error/warning when the target is created).
I wish I could do that, but decoding is very expensive and should be done
lazily. According to Intel and my tests, if a thread was traced during T
seconds, then decoding takes around 10T, which is a big amount of time if you
were tracing 10 threads for 5 seconds, which would take 500 seconds to decode.
At least for know we are not doing parallel decoding. I imagine at some point
we'll have to work on that.
Repository:
rG LLVM Github Monorepo
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https://reviews.llvm.org/D89283/new/
https://reviews.llvm.org/D89283
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