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[flang][OpenMP] Don't try to privatize FORALL/DO CONCURRENT indices #123341

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Merged
merged 2 commits into from
Jan 20, 2025
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[flang][OpenMP] Don't try to privatize FORALL/DO CONCURRENT indices #123341

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4e291f6
[flang][OpenMP] Don't try to privatize FORALL indices
luporl Jan 17, 2025
b1b5faa
Don't try to privatize DO CONCURRENT indices either
luporl Jan 17, 2025
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19 changes: 1 addition & 18 deletions flang/lib/Semantics/resolve-directives.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1777,28 +1777,13 @@ void OmpAttributeVisitor::ResolveSeqLoopIndexInParallelOrTaskConstruct(
// Use of DO CONCURRENT inside OpenMP construct is unspecified behavior
// till OpenMP-5.0 standard.
// In above both cases we skip the privatization of iteration variables.
// [OpenMP 5.1] DO CONCURRENT indices are private
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I guess it would be better to include a comment like the one below to explain why nothing is done for DO CONCURRENT in this function:

// DO CONCURRENT indices have predetermined private DSA, but as they are
// defined in the construct itself, and OpenMP directives may not appear in it,
// they are already private.

bool OmpAttributeVisitor::Pre(const parser::DoConstruct &x) {
if (!dirContext_.empty() && GetContext().withinConstruct) {
llvm::SmallVector<const parser::Name *> ivs;
if (x.IsDoNormal()) {
const parser::Name *iv{GetLoopIndex(x)};
if (iv && iv->symbol)
ivs.push_back(iv);
} else if (x.IsDoConcurrent()) {
const Fortran::parser::LoopControl *loopControl = &*x.GetLoopControl();
const Fortran::parser::LoopControl::Concurrent &concurrent =
std::get<Fortran::parser::LoopControl::Concurrent>(loopControl->u);
const Fortran::parser::ConcurrentHeader &concurrentHeader =
std::get<Fortran::parser::ConcurrentHeader>(concurrent.t);
const std::list<Fortran::parser::ConcurrentControl> &controls =
std::get<std::list<Fortran::parser::ConcurrentControl>>(
concurrentHeader.t);
for (const auto &control : controls) {
const parser::Name *iv{&std::get<0>(control.t)};
if (iv && iv->symbol)
ivs.push_back(iv);
}
}
ordCollapseLevel--;
for (auto iv : ivs) {
Expand All @@ -1810,9 +1795,6 @@ bool OmpAttributeVisitor::Pre(const parser::DoConstruct &x) {
if (ordCollapseLevel) {
if (const auto *details{iv->symbol->detailsIf<HostAssocDetails>()}) {
const Symbol *tpSymbol = &details->symbol();
// TODO: DoConcurrent won't capture the following check because a new
// symbol is declared in ResolveIndexName(), which will not have the
// OmpThreadprivate flag.
if (tpSymbol->test(Symbol::Flag::OmpThreadprivate)) {
context_.Say(iv->source,
"Loop iteration variable %s is not allowed in THREADPRIVATE."_err_en_US,
Expand Down Expand Up @@ -2119,6 +2101,7 @@ static bool IsPrivatizable(const Symbol *sym) {
*sym) && /* OpenMP 5.2, 5.1.1: Assumed-size arrays are shared*/
!sym->owner().IsDerivedType() &&
sym->owner().kind() != Scope::Kind::ImpliedDos &&
sym->owner().kind() != Scope::Kind::Forall &&
!sym->detailsIf<semantics::AssocEntityDetails>() &&
!sym->detailsIf<semantics::NamelistDetails>() &&
(!misc ||
Expand Down
10 changes: 7 additions & 3 deletions flang/test/Semantics/OpenMP/doconcurrent01.f90
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@@ -1,15 +1,19 @@
! RUN: %python %S/../test_symbols.py %s %flang_fc1 -fopenmp

! OpenMP 5.1.1
! DO Concurrent indices are private
! OpenMP 5.2 5.1.1 Variables Referenced in a Construct
! DO CONCURRENT indices have predetermined private DSA.
!
! As DO CONCURRENT indices are defined in the construct itself, and OpenMP
! directives may not appear in it, they are already private.
! Check that index symbols are not modified.

!DEF: /private_iv (Subroutine)Subprogram
subroutine private_iv
!DEF: /private_iv/i ObjectEntity INTEGER(4)
integer i
!$omp parallel default(private)
!$omp single
!DEF: /private_iv/OtherConstruct1/i (OmpPrivate, OmpPreDetermined) HostAssoc INTEGER(4)
!DEF: /private_iv/OtherConstruct1/OtherConstruct1/Forall1/i ObjectEntity INTEGER(4)
do concurrent(i=1:2)
end do
!$omp end single
Expand Down
32 changes: 32 additions & 0 deletions flang/test/Semantics/OpenMP/forall.f90
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@@ -0,0 +1,32 @@
! RUN: %python %S/../test_symbols.py %s %flang_fc1 -fopenmp

! OpenMP 5.2 5.1.1 Variables Referenced in a Construct
! FORALL indices have predetermined private DSA.
!
! As FORALL indices are defined in the construct itself, and OpenMP
! directives may not appear in it, they are already private.
! Check that index symbols are not modified.

!DEF: /MainProgram1/a ObjectEntity INTEGER(4)
!DEF: /MainProgram1/b ObjectEntity INTEGER(4)
integer a(5), b(5)

!REF: /MainProgram1/a
a = 0
!REF: /MainProgram1/b
b = 0

!$omp parallel
!DEF: /MainProgram1/OtherConstruct1/Forall1/i (Implicit) ObjectEntity INTEGER(4)
!DEF: /MainProgram1/OtherConstruct1/a HostAssoc INTEGER(4)
!DEF: /MainProgram1/OtherConstruct1/b HostAssoc INTEGER(4)
forall(i = 1:5) a(i) = b(i) * 2
!$omp end parallel

!$omp parallel default(private)
!DEF: /MainProgram1/OtherConstruct2/Forall1/i (Implicit) ObjectEntity INTEGER(4)
!DEF: /MainProgram1/OtherConstruct2/a (OmpPrivate) HostAssoc INTEGER(4)
!DEF: /MainProgram1/OtherConstruct2/b (OmpPrivate) HostAssoc INTEGER(4)
forall(i = 1:5) a(i) = b(i) * 2
!$omp end parallel
end program
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