[PATCH] D50004: [PowerPC] Emit xscpsgndp instead of xxlor when copying floating point scalar registers for P9

[Jinsong Ji via Phabricator via llvm-commits]

jsji added a comment.

In https://reviews.llvm.org/D50004#1187230, @amyk wrote:

> This revision primarily addresses enabling `xscpsgndp` for https://reviews.llvm.org/P9 only, as `xxlor` is still preferable to use for copying floating point scalars pre-P9.


No sure how much this will have impact, but maybe we need to consider still use xxlor for destructive instructions?

eg:
In Power ISA 3.0 B,  2.1.5 Destructive Operation Operand Preservation
"The set of instructions listed below, when immediately preceded by the xxlor XT,XC,XC instruction in a sequence similar to the above example, **will provide optimal performance.**"


https://reviews.llvm.org/D50004