[PATCH] D138766: [InstCombine] If loading from small alloca, load whole alloca and perform variable extraction

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Correction: while we can't do much for i128 case in general,
in the case i'm looking at, the upper half of the alloca is always zeros,
so after SROA, this becomes: https://alive2.llvm.org/ce/z/FgRHaZ,
and now that i128 codegen is rather good, isn't it?

I'm not quite sure we can/should factor that into profitability check though,
we'd need to look at other stores into alloca, etc.
But i'll look into at least teaching optimizations do that after SROA.


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https://reviews.llvm.org/D138766