Add sentinel value for AS2 on AMDGPU

Author: shiltian

clang/lib/Basic/Targets/AMDGPU.cpp

@@ -32,9 +32,9 @@ static const char *const DataLayoutStringR600 =
     "-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5-G1";
 
 static const char *const DataLayoutStringAMDGCN =
-    "e-p:64:64-p1:64:64-p2:32:32-p3:32:32:32:32:f-p4:64:64-p5:32:32:32:32:f"
-    "-p6:32:32-p7:160:256:256:32-p8:128:128-p9:192:256:256:32-i64:64-v16:16"
-    "-v24:32-v32:32-v48:64-v96:128"
+    "e-p:64:64-p1:64:64-p2:32:32:32:32:f-p3:32:32:32:32:f-p4:64:64"
+    "-p5:32:32:32:32:f-p6:32:32-p7:160:256:256:32-p8:128:128-p9:192:256:256:32"
+    "-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128"
     "-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5-G1"
     "-ni:7:8:9";