lower saturating add/sub in aarch64 GISel

Author: folkertdev

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

@@ -1795,6 +1795,14 @@ bool AArch64LegalizerInfo::legalizeIntrinsic(LegalizerHelper &Helper,
     MI.eraseFromParent();
     return true;
   }
+  case Intrinsic::aarch64_neon_sqadd:
+    return LowerBinOp(TargetOpcode::G_SADDSAT);
+  case Intrinsic::aarch64_neon_sqsub:
+    return LowerBinOp(TargetOpcode::G_SSUBSAT);
+  case Intrinsic::aarch64_neon_uqadd:
+    return LowerBinOp(TargetOpcode::G_UADDSAT);
+  case Intrinsic::aarch64_neon_uqsub:
+    return LowerBinOp(TargetOpcode::G_USUBSAT);
 
   case Intrinsic::vector_reverse:
     // TODO: Add support for vector_reverse