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[flang] Create temporaries for array sections passed to IGNORE_TKR dummy args #147419

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[flang] Create temporaries for array sections passed to IGNORE_TKR dummy args #147419

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2477076
[flang] Contiguity check on IGNORE_TKR argument
eugeneepshteyn Jul 4, 2025
50dd216
[flang] Add -pedantic check for passing non-VOLATILE array section to…
eugeneepshteyn Jul 7, 2025
383bdca
Merge branch 'llvm:main' into tkr-contiguous
eugeneepshteyn Jul 7, 2025
1e76690
Merge branch 'vol-actual-checks' into tkr-contiguous
eugeneepshteyn Jul 7, 2025
28cb65f
Undid change to definable.cpp
eugeneepshteyn Jul 7, 2025
a176d2d
The current implementation seems to work, but I will likely move some…
eugeneepshteyn Jul 7, 2025
96daba4
clang-format
eugeneepshteyn Jul 7, 2025
aace0c2
Some reformatting and comments
eugeneepshteyn Jul 7, 2025
5fdfb45
clang-format
eugeneepshteyn Jul 7, 2025
d105d0d
Merge branch 'llvm:main' into tkr-contiguous
eugeneepshteyn Jul 7, 2025
78fb202
Merge branch 'llvm:main' into tkr-contiguous
eugeneepshteyn Jul 9, 2025
bd1e8e6
Removed extra 'const' from the declaration
eugeneepshteyn Jul 9, 2025
a093fe6
LIT test
eugeneepshteyn Jul 9, 2025
63b2811
Test modification: added another check for when pass non-contiguous i…
eugeneepshteyn Jul 9, 2025
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3 changes: 3 additions & 0 deletions flang/include/flang/Evaluate/tools.h
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Expand Up @@ -1123,6 +1123,9 @@ extern template semantics::UnorderedSymbolSet CollectCudaSymbols(
// Predicate: does a variable contain a vector-valued subscript (not a triplet)?
bool HasVectorSubscript(const Expr<SomeType> &);

// Predicate: does a variable contain a triplet?
bool HasTriplet(const Expr<SomeType> &);

// Predicate: does an expression contain constant?
bool HasConstant(const Expr<SomeType> &);

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2 changes: 1 addition & 1 deletion flang/include/flang/Lower/CallInterface.h
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Expand Up @@ -170,7 +170,7 @@ class CallInterface {
/// Is the argument INTENT(OUT)
bool isIntentOut() const;
/// Does the argument have the CONTIGUOUS attribute or have explicit shape?
bool mustBeMadeContiguous() const;
bool mustBeMadeContiguous(const bool argHasTriplet = false) const;
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@klausler klausler Jul 8, 2025

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const is never needed in a prototype argument that isn't a reference or a pointer

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@eugeneepshteyn eugeneepshteyn Jul 8, 2025

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Why "never"? Maybe I just want to make it obvious that the arg shouldn't be modified:

void f(const bool x = false)
{
  x = true;
}

$ clang++ -c const.cpp
const.cpp:3:5: error: cannot assign to variable 'x' with const-qualified type 'const bool'
    3 |   x = true;
      |   ~ ^
const.cpp:1:19: note: variable 'x' declared const here
    1 | void f(const bool x = false)
      |        ~~~~~~~~~~~^~~~~~~~~
1 error generated.

In any case, this is not important to my change, so I can remove it.

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@klausler klausler Jul 8, 2025

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The prototype doesn't need the const here as part of the API, and the implementation is allowed to use const later if desired. So the const in the prototype makes me have to stop and wonder whether a & or * was intended but omitted.

/// Does the dummy argument have the VALUE attribute?
bool hasValueAttribute() const;
/// Does the dummy argument have the ALLOCATABLE attribute?
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16 changes: 16 additions & 0 deletions flang/lib/Evaluate/tools.cpp
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Expand Up @@ -1173,6 +1173,22 @@ bool HasVectorSubscript(const Expr<SomeType> &expr) {
return HasVectorSubscriptHelper{}(expr);
}

// HasTriplet()
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@eugeneepshteyn eugeneepshteyn Jul 8, 2025

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@klausler , could you please review HasTriplet part? I'll add the other reviewers for lowering, once I add the test.

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@klausler klausler Jul 8, 2025

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Simply checking for triplets is going to give false positives. A(:) is contiguous when A is; so are A(J:K) and A(J:K:1). There's a general contiguity checking facility in Evaluate that can handle questions of contiguity; have you tried using it?

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@eugeneepshteyn eugeneepshteyn Jul 8, 2025

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If mustBeMadeContiguous() returns true, then this eventually gets to isSimplyContiguous() which is a helper function that calls Fortran::evaluate::IsSimplyContiguous().

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@klausler klausler Jul 8, 2025

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And if mustBeMadeContiguous returns false, then IsSimplyContiguous is not called? Won't that lead to false negatives from e.g. A%X, non-CONTIGUOUS pointers, &c.?

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@eugeneepshteyn eugeneepshteyn Jul 8, 2025

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That would also be a problem with the current source, without my modifications. I'll check what happens in the cases you mentioned.

struct HasTripletHelper : public AnyTraverse<HasTripletHelper, bool,
/*TraverseAssocEntityDetails=*/false> {
using Base = AnyTraverse<HasTripletHelper, bool, false>;
HasTripletHelper() : Base{*this} {}
using Base::operator();
bool operator()(const Subscript &ss) const {
return std::holds_alternative<Triplet>(ss.u);
}
bool operator()(const ProcedureRef &) const {
return false; // don't descend into function call arguments
}
};

bool HasTriplet(const Expr<SomeType> &expr) { return HasTripletHelper{}(expr); }

// HasConstant()
struct HasConstantHelper : public AnyTraverse<HasConstantHelper, bool,
/*TraverseAssocEntityDetails=*/false> {
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14 changes: 12 additions & 2 deletions flang/lib/Lower/CallInterface.cpp
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Expand Up @@ -1416,16 +1416,26 @@ bool Fortran::lower::CallInterface<T>::PassedEntity::isIntentOut() const {
return true;
return characteristics->GetIntent() == Fortran::common::Intent::Out;
}

/// Returning "true" from this function is a prerequisite for running
/// contiguity check on the actual argument.
template <typename T>
bool Fortran::lower::CallInterface<T>::PassedEntity::mustBeMadeContiguous()
const {
bool Fortran::lower::CallInterface<T>::PassedEntity::mustBeMadeContiguous(
const bool argHasTriplet) const {
if (!characteristics)
return true;
const auto *dummy =
std::get_if<Fortran::evaluate::characteristics::DummyDataObject>(
&characteristics->u);
if (!dummy)
return false;
if (dummy->ignoreTKR.test(common::IgnoreTKR::Contiguous))
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@vzakhari vzakhari Jul 9, 2025

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This change makes sense to me, but I am not sure about the code below.

return false;

// TODO: should this check ignore "device" or "managed"?
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@eugeneepshteyn eugeneepshteyn Jul 7, 2025

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Reviewers, please answer this question

if (dummy->ignoreTKR.any() && argHasTriplet)
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@vzakhari vzakhari Jul 9, 2025

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Why do we care about whether the actual argument is an array section or not? Can it be a non-contiguous array (e.g. assumed shape dummy) that is passed as a dummy that is declared as IGNORE_TKR?

To fix #138471, can we return the following at line 1448?

return dummy->type.Rank() > 0 || dummy->ignoreTKR.test(common::IgnoreTKR::Rank);

return true;

const auto &shapeAttrs = dummy->type.attrs();
using ShapeAttrs = Fortran::evaluate::characteristics::TypeAndShape::Attr;
if (shapeAttrs.test(ShapeAttrs::AssumedRank) ||
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12 changes: 11 additions & 1 deletion flang/lib/Lower/ConvertCall.cpp
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Expand Up @@ -1255,11 +1255,21 @@ static PreparedDummyArgument preparePresentUserCallActualArgument(
passingPolymorphicToNonPolymorphic &&
(actual.isArray() || mlir::isa<fir::BaseBoxType>(dummyType));

// Helper function to make it easier to unwrap and use expression
auto argHasTriplet =
[](const Fortran::evaluate::ActualArgument &arg) -> bool {
if (const auto *expr = arg.UnwrapExpr())
return HasTriplet(*expr);
return false;
};

const bool actualHasTriplet = argHasTriplet(*arg.entity);

// The simple contiguity of the actual is "lost" when passing a polymorphic
// to a non polymorphic entity because the dummy dynamic type matters for
// the contiguity.
const bool mustDoCopyInOut =
actual.isArray() && arg.mustBeMadeContiguous() &&
actual.isArray() && arg.mustBeMadeContiguous(actualHasTriplet) &&
(passingPolymorphicToNonPolymorphic ||
!isSimplyContiguous(*arg.entity, foldingContext));

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