[PATCH] D113178: [PowerPC] use right register class for input operand of XXPERMDIs

[Nemanja Ivanovic via Phabricator via llvm-commits]

nemanjai added a comment.

I am not in favour of this patch. The reasons I added `XXPERMDIs` a long time ago are:

1. To allow a single input operand for single register splat/swap. This is useful when the input is a load (since due to chains, having a load as an input will end up with both loads emitted - i.e. no CSE).
2. Since this is primarily useful for loads that load a partial vector (LFIWZX, etc.) the input register class is `vsfrc` (i.e. all scalar floating point registers).

Switching the register class to `vsrc` does end up producing the name of a VSX register, but I consider that a positive thing. It clearly shows the reader that this is operating on a partial vector. Of course the distinction is purely aesthetic, but I think it helps readability.


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