Add description for mapper_id. Add verifier check for valid mapper_id.

Author: TIFitis

mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td

@@ -1077,6 +1077,8 @@ def MapInfoOp : OpenMP_Op<"map.info", [AttrSizedOperandSegments]> {
     - 'map_type': OpenMP map type for this map capture, for example: from, to and
        always. It's a bitfield composed of the OpenMP runtime flags stored in
        OpenMPOffloadMappingFlags.
+    - 'mapper_id': OpenMP mapper map type modifier for this map capture. It's used to
+       specify a user defined mapper to be used for mapping.
     - 'map_capture_type': Capture type for the variable e.g. this, byref, byvalue, byvla
        this can affect how the variable is lowered.
     - `name`: Holds the name of variable as specified in user clause (including bounds).

mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp

@@ -1631,6 +1631,12 @@ static LogicalResult verifyMapClause(Operation *op, OperandRange mapVars) {
 
         to ? updateToVars.insert(updateVar) : updateFromVars.insert(updateVar);
       }
+
+      if (mapInfoOp.getMapperId() &&
+          !SymbolTable::lookupNearestSymbolFrom<omp::DeclareMapperOp>(
+              mapInfoOp, mapInfoOp.getMapperIdAttr())) {
+        return emitError(op->getLoc(), "invalid mapper id");
+      }
     } else if (!isa<DeclareMapperInfoOp>(op)) {
       emitError(op->getLoc(), "map argument is not a map entry operation");
     }

mlir/test/Dialect/OpenMP/invalid.mlir

@@ -2842,3 +2842,13 @@ func.func @missing_workshare(%idx : index) {
   }
   return
 }
+
+// -----
+llvm.func @invalid_mapper(%0 : !llvm.ptr) {
+  %1 = omp.map.info var_ptr(%0 : !llvm.ptr, !llvm.struct<"my_type", (i32)>) mapper(@my_mapper) map_clauses(to) capture(ByRef) -> !llvm.ptr {name = ""}
+  // expected-error @below {{invalid mapper id}}
+  omp.target_data map_entries(%1 : !llvm.ptr) {
+    omp.terminator
+  }
+  llvm.return
+}