[PATCH] D64630: [DebugInfo] Address performance regression with r364515

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

In D64630#1583174 <https://reviews.llvm.org/D64630#1583174>, @probinson wrote:

> > With ASAN, packs of up to 800 DBG_VALUEs in a row appear (for that file)
>
> That seems excessive; in the past when I've seen this explosion of DBG instructions, the vast majority were redundant. Have you looked at them to see if this is the case?  We might rather eliminate duplicates than write code to make it cheaper to have lots of unnecessary instructions.


dbg.value packs are a major issue, ASan aside. I wrote this proposal a while back and never followed through on it:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/127228.html

With the lack of follow-through on my part, I think we should take Chris's suggestion of changing our representation to multiplex dbg.value, so that one instruction can describe an arbitrary number of variable locations without increasing the number of instructions that other passes have to iterate over.


Repository:
  rL LLVM

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https://reviews.llvm.org/D64630