[AArch64] Set FMOVS0 and FMOVD0 as isAsCheapAsAMove when needed.

If a subtarget has both ZCZeroing and CustomCheapAsMoveHandling features (now
only Kryo has both), set FMOVS0 and FMOVD0 isAsCheapAsAMove.

Differential Revision: http://reviews.llvm.org/D22256

llvm-svn: 275178

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index f5a5dd5894a..de881e75ce4 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -620,6 +620,12 @@ bool AArch64InstrInfo::isAsCheapAsAMove(const MachineInstr &MI) const {
     return canBeExpandedToORR(MI, 32);
   case AArch64::MOVi64imm:
     return canBeExpandedToORR(MI, 64);
+
+  // It is cheap to move #0 to float registers if the subtarget has 
+  // ZeroCycleZeroing feature.
+  case AArch64::FMOVS0:
+  case AArch64::FMOVD0:
+    return Subtarget.hasZeroCycleZeroing();
   }
 
   llvm_unreachable("Unknown opcode to check as cheap as a move!");