Emit a code for reduction clause. Next code should be emitted for reductions:
static kmp_critical_name lock = { 0 }; void reduce_func(void *lhs[<n>], void *rhs[<n>]) { *(Type0*)lhs[0] = ReductionOperation0(*(Type0*)lhs[0], *(Type0*)rhs[0]); ... *(Type<n>-1*)lhs[<n>-1] = ReductionOperation<n>-1(*(Type<n>-1*)lhs[<n>-1], *(Type<n>-1*)rhs[<n>-1]); } ... void *RedList[<n>] = {&<RHSExprs>[0], ..., &<RHSExprs>[<n>-1]}; switch (__kmpc_reduce{_nowait}(<loc>, <gtid>, <n>, sizeof(RedList), RedList, reduce_func, &<lock>)) { case 1: <LHSExprs>[0] = ReductionOperation0(*<LHSExprs>[0], *<RHSExprs>[0]); ... <LHSExprs>[<n>-1] = ReductionOperation<n>-1(*<LHSExprs>[<n>-1], *<RHSExprs>[<n>-1]); __kmpc_end_reduce{_nowait}(<loc>, <gtid>, &<lock>); break; case 2: Atomic(<LHSExprs>[0] = ReductionOperation0(*<LHSExprs>[0], *<RHSExprs>[0])); ... Atomic(<LHSExprs>[<n>-1] = ReductionOperation<n>-1(*<LHSExprs>[<n>-1], *<RHSExprs>[<n>-1])); break; default:; }
Reduction variables are a kind of a private variables, they have private copies, but initial values are chosen in accordance with the reduction operation.