[AArch64][GlobalISel] Legalize G_INTRINSIC_ROUND

Add it to the same rule as G_FCEIL etc. Add a legalizer test, and add a missing
switch case to AArch64LegalizerInfo.cpp.

llvm-svn: 359033
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 9521e67..c24418e 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1328,6 +1328,7 @@
   case TargetOpcode::G_FEXP2:
   case TargetOpcode::G_FPOW:
   case TargetOpcode::G_INTRINSIC_TRUNC:
+  case TargetOpcode::G_INTRINSIC_ROUND:
     assert(TypeIdx == 0);
     Observer.changingInstr(MI);