[PATCH] D135914: [PseudoProbe] Decode offset based pseudo probe.

Tue Oct 25 12:24:06 PDT 2022

wenlei added a comment.

In D135914#3882912 <https://reviews.llvm.org/D135914#3882912>, @hoy wrote:

> In D135914#3881607 <https://reviews.llvm.org/D135914#3881607>, @wenlei wrote:
>
>> Sentinel probe case isn't covered for both encoding and decoding in any test cases, would be good to have some coverage.
>
> Forgot to mention that the updated binary, i.e, inline-cs-pseudoprobe.perfbin, is built with the new encoding. The binary supports a dozen llvm-profgen tests and they all pass with the current decoding changes.

Do we have a split function case in the existing tests? I thought we don't, but if we have, that'd be good enough.

================
Comment at: llvm/lib/MC/MCPseudoProbe.cpp:476
+        // leading probe address or function start address.
+        EncodingIsAddrBased = true;
+      }
----------------
hoy wrote:
> wenlei wrote:
> > Maybe I'm asking the same question as the one on previous patch, but why do we still have cases with absolute address encoded? I thought for main function body we have GUID -> symbol (reverse lookup) -> address; and we have similar way to get address for sentinel for split binary function. The rest should all be offset/delta.
> This is mainly for downwards-compatibility, i.e. to have new llvm-profgen handle old binaries. 
Ok, makes sense. Like I mentioned in the other patch, add a comment explaining this is for backward compatibility and a todo for removal?

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  https://reviews.llvm.org/D135914/new/

https://reviews.llvm.org/D135914