[PATCH] D23614: [PPC] Generate positive FP zero using xor insn instead of loading from constant area

[Hal Finkel via llvm-commits]

hfinkel added a comment.

It does not need to be in the same commit as adds this scalar support, but we should also add a pattern to catch the vector case. For

  define <2 x double> @foo() local_unnamed_addr #0 {
    ret <2 x double> zeroinitializer
  }

we currently also load from memory. Actually, for this case on powerpc64le, there's another opportunity as well:

  	addis 3, 2, .LCPI0_0 at toc@ha
  	addi 3, 3, .LCPI0_0 at toc@l
  	lxvd2x 0, 0, 3
  	xxswapd	 34, 0
  	blr

Even in cases where we do need to load from memory, we should be able to fold the swap into the constant in cases where it can't otherwise be eliminated.


https://reviews.llvm.org/D23614