[PATCH] D55812: [PowerPC]Exploit P9 vabsdu for some unsigned integer vselect patterns

[Kewen Lin via Phabricator via llvm-commits]

jedilyn created this revision.
jedilyn added reviewers: nemanjai, jsji, hfinkel, echristo, inouehrs.
Herald added a subscriber: hiraditya.



  define <4 x i32> @absd_int32_ugt(<4 x i32>, <4 x i32>) {
    %3 = icmp ugt <4 x i32> %0, %1
    %4 = sub <4 x i32> %0, %1
    %5 = sub <4 x i32> %1, %0
    %6 = select <4 x i1> %3, <4 x i32> %4, <4 x i32> %5
    ret <4 x i32> %6
  }

For the above vector select case, even on Power9, we generate

  vcmpgtuw v4, v2, v3
  vsubuwm v5, v2, v3
  vsubuwm v2, v3, v2
  xxsel v2, v2, v5, v4
  blr

Power9 new instructions vabsdu* can be used and got the below optimized code:

  vabsduw v2, v2, v3
  blr


Repository:
  rL LLVM

https://reviews.llvm.org/D55812

Files:
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.h
  llvm/test/CodeGen/PowerPC/ppc64-P9-vabsd.ll

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