[AArch64] FMINNAN/FMAXNAN on f16 is not legal.

Spotted by Ahmed - in r244594 I inadvertently marked f16 min/max as legal.

I've reverted it here, and marked min/max on scalar f16's as promote. I've also added a testcase. The test just checks that the compiler doesn't fall over - it doesn't create fmin nodes for f16 yet.

llvm-svn: 245035
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 91a2db1..611cc48 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -301,6 +301,8 @@
   setOperationAction(ISD::FTRUNC,      MVT::f16,  Promote);
   setOperationAction(ISD::FMINNUM,     MVT::f16,  Promote);
   setOperationAction(ISD::FMAXNUM,     MVT::f16,  Promote);
+  setOperationAction(ISD::FMINNAN,     MVT::f16,  Promote);
+  setOperationAction(ISD::FMAXNAN,     MVT::f16,  Promote);
 
   // v4f16 is also a storage-only type, so promote it to v4f32 when that is
   // known to be safe.
@@ -681,8 +683,8 @@
                             ISD::SABSDIFF, ISD::UABSDIFF})
       setOperationAction(Opcode, VT.getSimpleVT(), Legal);
 
-  // F[MIN|MAX][NUM|NAN] are available for all FP NEON types.
-  if (VT.isFloatingPoint())
+  // F[MIN|MAX][NUM|NAN] are available for all FP NEON types (not f16 though!).
+  if (VT.isFloatingPoint() && VT.getVectorElementType() != MVT::f16)
     for (unsigned Opcode : {ISD::FMINNAN, ISD::FMAXNAN,
                             ISD::FMINNUM, ISD::FMAXNUM})
       setOperationAction(Opcode, VT.getSimpleVT(), Legal);