[PATCH] D129636: Fix a LSR debug invariance issue

[Stephen Tozer via Phabricator via llvm-commits]

StephenTozer added a comment.

In D129636#3716487 <https://reviews.llvm.org/D129636#3716487>, @jmorse wrote:

> I imagine you might find a different way expanding expressions for Values, depending on which PHIs you look at first, which changes if you look at the dbg.values first.

I thought that at first and was wondering if it was just an order-determined thing, which is always possible but could potentially be avoided by using something other than insertion order; in this case though it looks as though in the absence of the debug value, it does choose to insert a new instruction when a valid one already exists. It's not particularly relevant, since the existing behaviour is what it is and the patch needs to take that into account, it's just a slight surprise-factor that calling a `get` function and/or adding an item to a cache causes an instruction to be removed, although in the end it's almost sure to be removed anyway.


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https://reviews.llvm.org/D129636