OpenACC in Flang¶
The end directive for combined construct can omit the
!$acc routinewith no parallelism clause is treated as if the
seqclause was present.
!$acc end loopdoes not trigger a parsing error and is just ignored.
The restriction on
!$acc datarequired clauses is emitted as a portability warning instead of an error as other compiler accepts it.
ifclause accepts scalar integer expression in addition to scalar logical expression.
!$acc routinedirective can be placed at the top level.
!$acc cachedirective accepts scalar variable.
Array element references in the data clauses are equivalent to array sections consisting of this single element, i.e.
copyin(a(n))is equivalent to
copyin(a(n:n)). Some other implementations have treated it as
copyin(a(:n)), which does not correspond to OpenACC spec – Flang does not support this interpretation of an array element reference.