[CHERIoT] Fixes to cheriot_cap_import attribute

In particular, fix the mangling scheme of permissions ("" -> "-" when
permission not present) and, when checking for volatile qualifiers,
reach to pointee if type is pointer

Author: xdoardo

clang/lib/Sema/SemaDeclAttr.cpp

@@ -2117,7 +2117,10 @@ static void handleCHERIOTMMIODevice(Sema &S, Decl *D, const ParsedAttr &Attr,
   }
 
   QualType QT = VD->getType();
-  if (!QT.isVolatileQualified()) {
+  auto *PQT = dyn_cast<PointerType>(QT);
+  auto IsVolatile = (PQT && PQT->getPointeeType().isVolatileQualified()) ||
+                    QT.isVolatileQualified();
+  if (!IsVolatile) {
     S.Diag(Attr.getLoc(), diag::warn_cheriot_global_cap_import_non_volatile)
         << VD->getName() << Attr.getAttrName();
   }

clang/test/CodeGen/cheri/riscv/cheriot-cap-import-attr.c

@@ -176,15 +176,15 @@ void func() {
 
 // CHECK: attributes #0 = { "cheriot_global_cap_import"="mem,uart,RWcm" }
 // CHECK: attributes #1 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,RWcm" }
-// CHECK: attributes #2 = { "cheriot_global_cap_import"="mem,uart,R" }
-// CHECK: attributes #3 = { "cheriot_global_cap_import"="mem,uart,Rc" }
-// CHECK: attributes #4 = { "cheriot_global_cap_import"="mem,uart,Rcm" }
-// CHECK: attributes #5 = { "cheriot_global_cap_import"="mem,uart,W" }
-// CHECK: attributes #6 = { "cheriot_global_cap_import"="mem,uart,Wc" }
-// CHECK: attributes #7 = { "cheriot_global_cap_import"="mem,uart,RWc" }
-// CHECK: attributes #8 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,R" }
-// CHECK: attributes #9 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,Rc" }
-// CHECK: attributes #10 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,Rcm" }
-// CHECK: attributes #11 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,W" }
-// CHECK: attributes #12 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,Wc" }
-// CHECK: attributes #13 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,RWc" }
+// CHECK: attributes #2 = { "cheriot_global_cap_import"="mem,uart,R---" }
+// CHECK: attributes #3 = { "cheriot_global_cap_import"="mem,uart,R-c-" }
+// CHECK: attributes #4 = { "cheriot_global_cap_import"="mem,uart,R-cm" }
+// CHECK: attributes #5 = { "cheriot_global_cap_import"="mem,uart,-W--" }
+// CHECK: attributes #6 = { "cheriot_global_cap_import"="mem,uart,-Wc-" }
+// CHECK: attributes #7 = { "cheriot_global_cap_import"="mem,uart,RWc-" }
+// CHECK: attributes #8 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,R---" }
+// CHECK: attributes #9 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,R-c-" }
+// CHECK: attributes #10 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,R-cm" }
+// CHECK: attributes #11 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,-W--" }
+// CHECK: attributes #12 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,-Wc-" }
+// CHECK: attributes #13 = { "cheriot_global_cap_import"="cheriot_shared_object,SO,RWc-" }

llvm/include/llvm/IR/Attributes.h

@@ -1498,10 +1498,10 @@ class CHERIoTGlobalCapabilityImportAttr {
       return false;
     }
 
-    Permissions = (HasRead ? std::string(ReadPermissionSymbol) : "") +
-                  (HasWrite ? std::string(WritePermissionSymbol) : "") +
-                  (HasCap ? std::string(CapPermissionSymbol) : "") +
-                  (HasMut ? std::string(MutPermissionSymbol) : "");
+    Permissions = (HasRead ? std::string(ReadPermissionSymbol) : "-") +
+                  (HasWrite ? std::string(WritePermissionSymbol) : "-") +
+                  (HasCap ? std::string(CapPermissionSymbol) : "-") +
+                  (HasMut ? std::string(MutPermissionSymbol) : "-");
     return true;
   }