Address PR comments, change diag string to indicate an intrinsic is not supported

Author: farzonl

llvm/lib/Target/DirectX/DXILOpLowering.cpp

@@ -778,7 +778,8 @@ class OpLowerer {
       case Intrinsic::not_intrinsic:
         continue;
       default: {
-        DiagnosticInfoUnsupported Diag(F, "Unknown intrinsic?");
+        DiagnosticInfoUnsupported Diag(
+            F, "Unsupported intrinsic for DXIL lowering");
         M.getContext().diagnose(Diag);
         HasErrors |= true;
         break;

llvm/test/CodeGen/DirectX/unknown_intrinsic.ll renamed to llvm/test/CodeGen/DirectX/unsupported_intrinsic.ll

@@ -1,6 +1,6 @@
 ; RUN: not opt -S -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s 2>&1 | FileCheck %s
 
-; CHECK: error: <unknown>:0:0: in function llvm.vector.reduce.and.v4i32 i32 (<4 x i32>): Unknown intrinsic?
+; CHECK: error: <unknown>:0:0: in function llvm.vector.reduce.and.v4i32 i32 (<4 x i32>): Unsupported intrinsic for DXIL lowering
 define i32 @fn_and(<4 x i32> %0) local_unnamed_addr #0 {
   %2 = tail call i32 @llvm.vector.reduce.and.v4i32(<4 x i32> %0)
   ret i32 %2