[flang-commits] [flang] [flang] Relax constraints on PURE/ELEMENTAL dummy arguments (PR #93748)
Peter Klausler via flang-commits
flang-commits at lists.llvm.org
Mon Jun 3 11:57:19 PDT 2024
https://github.com/klausler updated https://github.com/llvm/llvm-project/pull/93748
>From 05eca0a9d9fbbaa8223432d8e570d5638c6f4c82 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Wed, 29 May 2024 15:45:47 -0700
Subject: [PATCH] [flang] Relax constraints on PURE/ELEMENTAL dummy arguments
The standard requires that dummy arguments to PURE functions
be INTENT(IN) or VALUE, but PURE subroutines are allowed to
have modifiable dummy arguments. This makes it impossible to
declare atomic operations as PURE functions, which consequently
makes such atomic operations ineligible for use in parallel
constructs and DO CONCURRENT.
This patch downgrades this error to a warning by default, which
can be seen with -pedantic & al. and remain an error with -Werror.
---
flang/docs/Extensions.md | 6 +++
flang/include/flang/Common/Fortran-features.h | 2 +-
flang/lib/Semantics/check-declarations.cpp | 37 ++++++++++++++-----
flang/test/Semantics/call10.f90 | 6 +--
flang/test/Semantics/elemental01.f90 | 2 +-
5 files changed, 39 insertions(+), 14 deletions(-)
diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
index 7b872c786c82c..bbda7c2aa2541 100644
--- a/flang/docs/Extensions.md
+++ b/flang/docs/Extensions.md
@@ -118,6 +118,12 @@ end
procedure interface. This compiler accepts it, since there is otherwise
no way to declare an interoperable dummy procedure with an arbitrary
interface like `void (*)()`.
+* `PURE` functions are allowed to have dummy arguments that are
+ neither `INTENT(IN)` nor `VALUE`, similar to `PURE` subroutines,
+ with a warning.
+ This enables atomic memory operations to be naturally represented
+ as `PURE` functions, which allows their use in parallel constructs
+ and `DO CONCURRENT`.
## Extensions, deletions, and legacy features supported by default
diff --git a/flang/include/flang/Common/Fortran-features.h b/flang/include/flang/Common/Fortran-features.h
index 15c4af63f4be7..fcd44bf68c9b2 100644
--- a/flang/include/flang/Common/Fortran-features.h
+++ b/flang/include/flang/Common/Fortran-features.h
@@ -50,7 +50,7 @@ ENUM_CLASS(LanguageFeature, BackslashEscapes, OldDebugLines,
EmptySequenceType, NonSequenceCrayPointee, BranchIntoConstruct,
BadBranchTarget, ConvertedArgument, HollerithPolymorphic, ListDirectedSize,
NonBindCInteroperability, CudaManaged, CudaUnified,
- PolymorphicActualAllocatableOrPointerToMonomorphicDummy)
+ PolymorphicActualAllocatableOrPointerToMonomorphicDummy, RelaxedPureDummy)
// Portability and suspicious usage warnings
ENUM_CLASS(UsageWarning, Portability, PointerToUndefinable,
diff --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
index 7034902dcc58d..25de9d4af1ffb 100644
--- a/flang/lib/Semantics/check-declarations.cpp
+++ b/flang/lib/Semantics/check-declarations.cpp
@@ -704,29 +704,48 @@ void CheckHelper::CheckObjectEntity(
if (InPure() && !IsStmtFunction(DEREF(innermostSymbol_)) &&
!IsPointer(symbol) && !IsIntentIn(symbol) &&
!symbol.attrs().test(Attr::VALUE)) {
- if (InFunction()) { // C1583
- messages_.Say(
- "non-POINTER dummy argument of pure function must be INTENT(IN) or VALUE"_err_en_US);
- } else if (IsIntentOut(symbol)) {
+ const char *what{InFunction() ? "function" : "subroutine"};
+ bool ok{true};
+ if (IsIntentOut(symbol)) {
if (type && type->IsPolymorphic()) { // C1588
messages_.Say(
- "An INTENT(OUT) dummy argument of a pure subroutine may not be polymorphic"_err_en_US);
+ "An INTENT(OUT) dummy argument of a pure %s may not be polymorphic"_err_en_US,
+ what);
+ ok = false;
} else if (derived) {
if (FindUltimateComponent(*derived, [](const Symbol &x) {
const DeclTypeSpec *type{x.GetType()};
return type && type->IsPolymorphic();
})) { // C1588
messages_.Say(
- "An INTENT(OUT) dummy argument of a pure subroutine may not have a polymorphic ultimate component"_err_en_US);
+ "An INTENT(OUT) dummy argument of a pure %s may not have a polymorphic ultimate component"_err_en_US,
+ what);
+ ok = false;
}
if (HasImpureFinal(symbol)) { // C1587
messages_.Say(
- "An INTENT(OUT) dummy argument of a pure subroutine may not have an impure FINAL subroutine"_err_en_US);
+ "An INTENT(OUT) dummy argument of a pure %s may not have an impure FINAL subroutine"_err_en_US,
+ what);
+ ok = false;
}
}
} else if (!IsIntentInOut(symbol)) { // C1586
messages_.Say(
- "non-POINTER dummy argument of pure subroutine must have INTENT() or VALUE attribute"_err_en_US);
+ "non-POINTER dummy argument of pure %s must have INTENT() or VALUE attribute"_warn_en_US,
+ what);
+ ok = false;
+ }
+ if (ok && InFunction()) {
+ if (context_.IsEnabled(common::LanguageFeature::RelaxedPureDummy)) {
+ if (context_.ShouldWarn(common::LanguageFeature::RelaxedPureDummy) &&
+ !InModuleFile() && !InElemental()) {
+ messages_.Say(
+ "non-POINTER dummy argument of pure function should be INTENT(IN) or VALUE"_warn_en_US);
+ }
+ } else {
+ messages_.Say(
+ "non-POINTER dummy argument of pure function must be INTENT(IN) or VALUE"_err_en_US);
+ }
}
}
if (auto ignoreTKR{GetIgnoreTKR(symbol)}; !ignoreTKR.empty()) {
@@ -798,7 +817,7 @@ void CheckHelper::CheckObjectEntity(
"A dummy argument of an ELEMENTAL procedure may not be a POINTER"_err_en_US);
}
if (!symbol.attrs().HasAny(Attrs{Attr::VALUE, Attr::INTENT_IN,
- Attr::INTENT_INOUT, Attr::INTENT_OUT})) { // C15102
+ Attr::INTENT_INOUT, Attr::INTENT_OUT})) { // F'2023 C15120
messages_.Say(
"A dummy argument of an ELEMENTAL procedure must have an INTENT() or VALUE attribute"_err_en_US);
}
diff --git a/flang/test/Semantics/call10.f90 b/flang/test/Semantics/call10.f90
index b1f3528227497..ff19f104b051b 100644
--- a/flang/test/Semantics/call10.f90
+++ b/flang/test/Semantics/call10.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_errors.py %s %flang_fc1
+! RUN: %python %S/test_errors.py %s %flang_fc1 -pedantic
! Test 15.7 (C1583-C1590, C1592-C1599) constraints and restrictions
! for pure procedures.
! (C1591 is tested in call11.f90; C1594 in call12.f90.)
@@ -53,14 +53,14 @@ pure real function f02(a)
real, value :: a ! ok
end function
pure real function f03(a) ! C1583
- !ERROR: non-POINTER dummy argument of pure function must be INTENT(IN) or VALUE
+ !ERROR: non-POINTER dummy argument of pure function must have INTENT() or VALUE attribute
real :: a
end function
pure real function f03a(a)
real, pointer :: a ! ok
end function
pure real function f04(a) ! C1583
- !ERROR: non-POINTER dummy argument of pure function must be INTENT(IN) or VALUE
+ !WARNING: non-POINTER dummy argument of pure function should be INTENT(IN) or VALUE
real, intent(out) :: a
end function
pure real function f04a(a)
diff --git a/flang/test/Semantics/elemental01.f90 b/flang/test/Semantics/elemental01.f90
index 8a80727da45ef..6b2b25907ef60 100644
--- a/flang/test/Semantics/elemental01.f90
+++ b/flang/test/Semantics/elemental01.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_errors.py %s %flang_fc1
+! RUN: %python %S/test_errors.py %s %flang_fc1 -pedantic
! Tests ELEMENTAL subprogram constraints C15100-15102
!ERROR: An ELEMENTAL subroutine may not have an alternate return dummy argument
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