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Jun 18, 2025
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[flang][OpenMP] Clarify confusing error message #144707

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57 changes: 38 additions & 19 deletions flang/lib/Semantics/check-omp-structure.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3510,37 +3510,56 @@ void OmpStructureChecker::CheckAtomicUpdateAssignment(
operation::ToString(top.first));
return;
}
// Check if `atom` occurs exactly once in the argument list.
// Check how many times `atom` occurs as an argument, if it's a subexpression
// of an argument, and collect the non-atom arguments.
std::vector<SomeExpr> nonAtom;
auto unique{[&]() { // -> iterator
auto found{top.second.end()};
for (auto i{top.second.begin()}, e{top.second.end()}; i != e; ++i) {
if (IsSameOrConvertOf(*i, atom)) {
if (found != top.second.end()) {
return top.second.end();
}
found = i;
MaybeExpr subExpr;
auto atomCount{[&]() {
int count{0};
for (const SomeExpr &arg : top.second) {
if (IsSameOrConvertOf(arg, atom)) {
++count;
} else {
nonAtom.push_back(*i);
if (!subExpr && IsSubexpressionOf(atom, arg)) {
subExpr = arg;
}
nonAtom.push_back(arg);
}
}
return found;
return count;
}()};

if (unique == top.second.end()) {
if (top.first == operation::Operator::Identity) {
// This is "x = y".
bool hasError{false};
if (subExpr) {
context_.Say(rsrc,
"The atomic variable %s cannot be a proper subexpression of an argument (here: %s) in the update operation"_err_en_US,
atom.AsFortran(), subExpr->AsFortran());
hasError = true;
}
if (top.first == operation::Operator::Identity) {
// This is "x = y".
assert((atomCount == 0 || atomCount == 1) && "Unexpected count");
if (atomCount == 0) {
context_.Say(rsrc,
"The atomic variable %s should appear as an argument in the update operation"_err_en_US,
atom.AsFortran());
} else {
assert(top.first != operation::Operator::Identity &&
"Handle this separately");
hasError = true;
}
} else {
if (atomCount == 0) {
context_.Say(rsrc,
"The atomic variable %s should appear as an argument of the top-level %s operator"_err_en_US,
atom.AsFortran(), operation::ToString(top.first));
hasError = true;
} else if (atomCount > 1) {
context_.Say(rsrc,
"The atomic variable %s should occur exactly once among the arguments of the top-level %s operator"_err_en_US,
"The atomic variable %s should be exactly one of the arguments of the top-level %s operator"_err_en_US,
atom.AsFortran(), operation::ToString(top.first));
hasError = true;
}
} else {
}

if (!hasError) {
CheckStorageOverlap(atom, nonAtom, source);
}
}
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3 changes: 2 additions & 1 deletion flang/test/Semantics/OpenMP/atomic-update-only.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,8 @@ subroutine f03
integer :: x, y

!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable x cannot be a proper subexpression of an argument (here: (x+y)) in the update operation
!ERROR: The atomic variable x should appear as an argument of the top-level + operator
x = (x + y) + 1
end

Expand Down
32 changes: 16 additions & 16 deletions flang/test/Semantics/OpenMP/atomic03.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -25,19 +25,19 @@ program OmpAtomic
y = MIN(y, 8)

!$omp atomic
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level AND operator
!ERROR: The atomic variable z should appear as an argument of the top-level AND operator
z = IAND(y, 4)
!$omp atomic
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level OR operator
!ERROR: The atomic variable z should appear as an argument of the top-level OR operator
z = IOR(y, 5)
!$omp atomic
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level NEQV/EOR operator
!ERROR: The atomic variable z should appear as an argument of the top-level NEQV/EOR operator
z = IEOR(y, 6)
!$omp atomic
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level MAX operator
!ERROR: The atomic variable z should appear as an argument of the top-level MAX operator
z = MAX(y, 7, b, c)
!$omp atomic
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level MIN operator
!ERROR: The atomic variable z should appear as an argument of the top-level MIN operator
z = MIN(y, 8, a, d)

!$omp atomic
Expand All @@ -58,19 +58,19 @@ program OmpAtomic
y = MIN(y, 8)

!$omp atomic update
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level AND operator
!ERROR: The atomic variable z should appear as an argument of the top-level AND operator
z = IAND(y, 4)
!$omp atomic update
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level OR operator
!ERROR: The atomic variable z should appear as an argument of the top-level OR operator
z = IOR(y, 5)
!$omp atomic update
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level NEQV/EOR operator
!ERROR: The atomic variable z should appear as an argument of the top-level NEQV/EOR operator
z = IEOR(y, 6)
!$omp atomic update
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level MAX operator
!ERROR: The atomic variable z should appear as an argument of the top-level MAX operator
z = MAX(y, 7)
!$omp atomic update
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level MIN operator
!ERROR: The atomic variable z should appear as an argument of the top-level MIN operator
z = MIN(y, 8)

!$omp atomic update
Expand All @@ -90,7 +90,7 @@ subroutine conflicting_types()
type(simple) ::s
z = 1
!$omp atomic
!ERROR: The atomic variable z should occur exactly once among the arguments of the top-level AND operator
!ERROR: The atomic variable z should appear as an argument of the top-level AND operator
z = IAND(s%z, 4)
end subroutine

Expand All @@ -103,30 +103,30 @@ subroutine more_invalid_atomic_update_stmts()
type(some_type) :: s

!$omp atomic update
!ERROR: The atomic variable a should occur exactly once among the arguments of the top-level MIN operator
!ERROR: The atomic variable a should be exactly one of the arguments of the top-level MIN operator
a = min(a, a, b)

!$omp atomic
!ERROR: The atomic variable a should occur exactly once among the arguments of the top-level MAX operator
!ERROR: The atomic variable a should be exactly one of the arguments of the top-level MAX operator
a = max(b, a, b, a)

!$omp atomic
a = min(b, a, b)

!$omp atomic
!ERROR: The atomic variable a should occur exactly once among the arguments of the top-level MAX operator
!ERROR: The atomic variable a should be exactly one of the arguments of the top-level MAX operator
a = max(b, a, b, a, b)

!$omp atomic update
!ERROR: The atomic variable y should occur exactly once among the arguments of the top-level MIN operator
!ERROR: The atomic variable y should appear as an argument of the top-level MIN operator
y = min(z, x)

!$omp atomic
z = max(z, y)

!$omp atomic update
!ERROR: Atomic variable k should be a scalar
!ERROR: The atomic variable k should occur exactly once among the arguments of the top-level MAX operator
!ERROR: The atomic variable k should appear as an argument of the top-level MAX operator
k = max(x, y)

!$omp atomic
Expand Down
60 changes: 32 additions & 28 deletions flang/test/Semantics/OpenMP/atomic04.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -17,21 +17,21 @@ program OmpAtomic
!$omp atomic
x = 1 + x
!$omp atomic
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable x should appear as an argument of the top-level + operator
x = y + 1
!$omp atomic
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable x should appear as an argument of the top-level + operator
x = 1 + y

!$omp atomic
x = x - 1
!$omp atomic
x = 1 - x
!$omp atomic
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level - operator
!ERROR: The atomic variable x should appear as an argument of the top-level - operator
x = y - 1
!$omp atomic
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level - operator
!ERROR: The atomic variable x should appear as an argument of the top-level - operator
x = 1 - y

!$omp atomic
Expand All @@ -50,64 +50,64 @@ program OmpAtomic
!$omp atomic
x = 1/x
!$omp atomic
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level / operator
!ERROR: The atomic variable x should appear as an argument of the top-level / operator
x = y/1
!$omp atomic
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level / operator
!ERROR: The atomic variable x should appear as an argument of the top-level / operator
x = 1/y

!$omp atomic
m = m .AND. n
!$omp atomic
m = n .AND. m
!$omp atomic
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level AND operator
!ERROR: The atomic variable m should appear as an argument of the top-level AND operator
m = n .AND. l

!$omp atomic
m = m .OR. n
!$omp atomic
m = n .OR. m
!$omp atomic
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level OR operator
!ERROR: The atomic variable m should appear as an argument of the top-level OR operator
m = n .OR. l

!$omp atomic
m = m .EQV. n
!$omp atomic
m = n .EQV. m
!$omp atomic
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level EQV operator
!ERROR: The atomic variable m should appear as an argument of the top-level EQV operator
m = n .EQV. l

!$omp atomic
m = m .NEQV. n
!$omp atomic
m = n .NEQV. m
!$omp atomic
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level NEQV/EOR operator
!ERROR: The atomic variable m should appear as an argument of the top-level NEQV/EOR operator
m = n .NEQV. l

!$omp atomic update
x = x + 1
!$omp atomic update
x = 1 + x
!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable x should appear as an argument of the top-level + operator
x = y + 1
!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable x should appear as an argument of the top-level + operator
x = 1 + y

!$omp atomic update
x = x - 1
!$omp atomic update
x = 1 - x
!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level - operator
!ERROR: The atomic variable x should appear as an argument of the top-level - operator
x = y - 1
!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level - operator
!ERROR: The atomic variable x should appear as an argument of the top-level - operator
x = 1 - y

!$omp atomic update
Expand All @@ -126,42 +126,42 @@ program OmpAtomic
!$omp atomic update
x = 1/x
!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level / operator
!ERROR: The atomic variable x should appear as an argument of the top-level / operator
x = y/1
!$omp atomic update
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level / operator
!ERROR: The atomic variable x should appear as an argument of the top-level / operator
x = 1/y

!$omp atomic update
m = m .AND. n
!$omp atomic update
m = n .AND. m
!$omp atomic update
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level AND operator
!ERROR: The atomic variable m should appear as an argument of the top-level AND operator
m = n .AND. l

!$omp atomic update
m = m .OR. n
!$omp atomic update
m = n .OR. m
!$omp atomic update
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level OR operator
!ERROR: The atomic variable m should appear as an argument of the top-level OR operator
m = n .OR. l

!$omp atomic update
m = m .EQV. n
!$omp atomic update
m = n .EQV. m
!$omp atomic update
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level EQV operator
!ERROR: The atomic variable m should appear as an argument of the top-level EQV operator
m = n .EQV. l

!$omp atomic update
m = m .NEQV. n
!$omp atomic update
m = n .NEQV. m
!$omp atomic update
!ERROR: The atomic variable m should occur exactly once among the arguments of the top-level NEQV/EOR operator
!ERROR: The atomic variable m should appear as an argument of the top-level NEQV/EOR operator
m = n .NEQV. l

end program OmpAtomic
Expand All @@ -184,27 +184,30 @@ subroutine more_invalid_atomic_update_stmts()
x = 1

!$omp atomic update
!ERROR: Within atomic operation a and a*b access the same storage
!ERROR: The atomic variable a cannot be a proper subexpression of an argument (here: a*b) in the update operation
a = a * b + a

!$omp atomic
!ERROR: The atomic variable a should occur exactly once among the arguments of the top-level * operator
!ERROR: The atomic variable a cannot be a proper subexpression of an argument (here: (a+9_4)) in the update operation
!ERROR: The atomic variable a should appear as an argument of the top-level * operator
a = b * (a + 9)

!$omp atomic update
!ERROR: Within atomic operation a and (a+b) access the same storage
!ERROR: The atomic variable a cannot be a proper subexpression of an argument (here: (a+b)) in the update operation
a = a * (a + b)

!$omp atomic
!ERROR: Within atomic operation a and (b+a) access the same storage
!ERROR: The atomic variable a cannot be a proper subexpression of an argument (here: (b+a)) in the update operation
a = (b + a) * a

!$omp atomic
!ERROR: The atomic variable a should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable a cannot be a proper subexpression of an argument (here: a*b) in the update operation
!ERROR: The atomic variable a should appear as an argument of the top-level + operator
a = a * b + c

!$omp atomic update
!ERROR: The atomic variable a should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable a cannot be a proper subexpression of an argument (here: a+b) in the update operation
!ERROR: The atomic variable a should appear as an argument of the top-level + operator
a = a + b + c

!$omp atomic
Expand All @@ -219,11 +222,12 @@ subroutine more_invalid_atomic_update_stmts()

!$omp atomic update
!ERROR: No intrinsic or user-defined ASSIGNMENT(=) matches scalar REAL(4) and rank 1 array of REAL(4)
!ERROR: The atomic variable x should occur exactly once among the arguments of the top-level / operator
!ERROR: The atomic variable x cannot be a proper subexpression of an argument (here: x*y) in the update operation
!ERROR: The atomic variable x should appear as an argument of the top-level / operator
x = x * y / z

!$omp atomic
!ERROR: The atomic variable p%m should occur exactly once among the arguments of the top-level + operator
!ERROR: The atomic variable p%m should appear as an argument of the top-level + operator
p%m = x + y

!$omp atomic update
Expand Down
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