[PATCH] D56008: [ARM] Alter the register allocation order for optsize on Thumb2

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Hello

I had not seen that, thanks for pointing to it. Yes, this is a bit simpler, not trying to deal with r12. Just using the default allocation order only gets us so far, but it seems like a simple enough change. I had tried a few different orderings around using r4/r7 before lr, for example, as they are often spilled in pairs, but this seemed to give the best results for the codebases I tried.

I would say that this patch get us a little bit of codesize in many places, adding up to a good overall gain. Compared to all the other codefolding/libcall style changes we might try to make (that would occur in less places), this seems like an easier win for a simple change.


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https://reviews.llvm.org/D56008