[llvm] r275503 - [AArch64] Set COPY ZR isAsCheapAsAMove when needed.

[Haicheng Wu via llvm-commits]

Author: haicheng
Date: Thu Jul 14 19:27:01 2016
New Revision: 275503

URL: http://llvm.org/viewvc/llvm-project?rev=275503&view=rev
Log:
[AArch64] Set COPY ZR isAsCheapAsAMove when needed.

If a subtarget has both ZCZeroing and CustomCheapAsMoveHandling features (now
only Kryo has both), set COPY (W|X)ZR isAsCheapAsAMove.

Differential Revision: http://reviews.llvm.org/D22360

Modified:
    llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp

Modified: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp?rev=275503&r1=275502&r2=275503&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp Thu Jul 14 19:27:01 2016
@@ -624,11 +624,15 @@ bool AArch64InstrInfo::isAsCheapAsAMove(
   case AArch64::MOVi64imm:
     return canBeExpandedToORR(MI, 64);
 
-  // It is cheap to move #0 to float registers if the subtarget has 
-  // ZeroCycleZeroing feature.
+  // It is cheap to zero out registers if the subtarget has ZeroCycleZeroing
+  // feature.
   case AArch64::FMOVS0:
   case AArch64::FMOVD0:
     return Subtarget.hasZeroCycleZeroing();
+  case TargetOpcode::COPY:
+    return (Subtarget.hasZeroCycleZeroing() &&
+            (MI.getOperand(1).getReg() == AArch64::WZR ||
+             MI.getOperand(1).getReg() == AArch64::XZR));
   }
 
   llvm_unreachable("Unknown opcode to check as cheap as a move!");