This patch implements the parsing and sema support for OpenMP to clause with potential user-defined mappers attached. User defined mapper is a new feature in OpenMP 5.0. A to/from clause can have an explicit or implicit associated mapper, which instructs the compiler to generate and use customized mapping functions. An example is shown below:
struct S { int len; int *d; }; #pragma omp declare mapper(id: struct S s) map(s, s.d[0:s.len]) struct S ss; #pragma omp target update to(mapper(id): ss) // use the mapper with name 'id' to map ss to device