[flang-commits] [flang] [flang][semantics][OpenMP] no privatisation of stmt functions (PR #106550)

[Tom Eccles via flang-commits]

https://github.com/tblah updated https://github.com/llvm/llvm-project/pull/106550

>From fb8b074c0fa9d86f578a439f8121cb76a05e61c0 Mon Sep 17 00:00:00 2001
From: Tom Eccles <tom.eccles at arm.com>
Date: Thu, 29 Aug 2024 10:19:56 +0000
Subject: [PATCH 1/2] [flang][semantics][OpenMP] no privatisation of stmt
 functions

OpenMP prohibits privatisation of variables that appear in expressions
for statement functions.

This is a re-working of an old patch https://reviews.llvm.org/D93213 by
@praveen-g-ctt.

The old patch couldn't be landed because of ordering concerns. Statement
functions are rewritten during parse tree rewriting, but this was done
after resolve-directives and so some array expressions were incorrectly
identified as statement functions. For this reason **I have opted to
re-order the semantics driver so that resolve-directives is run after
parse tree rewriting**.

Closes #54677

Co-authored-by: Praveen <praveen at compilertree.com>
---
 flang/lib/Semantics/resolve-directives.cpp | 14 ++++++--
 flang/lib/Semantics/semantics.cpp          |  2 +-
 flang/test/Semantics/OpenMP/private03.f90  | 39 ++++++++++++++++++++++
 3 files changed, 51 insertions(+), 4 deletions(-)
 create mode 100644 flang/test/Semantics/OpenMP/private03.f90

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 4aecb8b8e7b479..8e21dead15bf9c 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -717,7 +717,7 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
   void CheckDataCopyingClause(
       const parser::Name &, const Symbol &, Symbol::Flag);
   void CheckAssocLoopLevel(std::int64_t level, const parser::OmpClause *clause);
-  void CheckObjectInNamelist(
+  void CheckPrivateDSAObject(
       const parser::Name &, const Symbol &, Symbol::Flag);
   void CheckSourceLabel(const parser::Label &);
   void CheckLabelContext(const parser::CharBlock, const parser::CharBlock,
@@ -2349,7 +2349,7 @@ void OmpAttributeVisitor::ResolveOmpObject(
                     CheckMultipleAppearances(*name, *symbol, ompFlag);
                   }
                   if (privateDataSharingAttributeFlags.test(ompFlag)) {
-                    CheckObjectInNamelist(*name, *symbol, ompFlag);
+                    CheckPrivateDSAObject(*name, *symbol, ompFlag);
                   }
 
                   if (ompFlag == Symbol::Flag::OmpAllocate) {
@@ -2706,7 +2706,7 @@ void OmpAttributeVisitor::CheckDataCopyingClause(
   }
 }
 
-void OmpAttributeVisitor::CheckObjectInNamelist(
+void OmpAttributeVisitor::CheckPrivateDSAObject(
     const parser::Name &name, const Symbol &symbol, Symbol::Flag ompFlag) {
   const auto &ultimateSymbol{symbol.GetUltimate()};
   llvm::StringRef clauseName{"PRIVATE"};
@@ -2721,6 +2721,14 @@ void OmpAttributeVisitor::CheckObjectInNamelist(
         "Variable '%s' in NAMELIST cannot be in a %s clause"_err_en_US,
         name.ToString(), clauseName.str());
   }
+
+  if (stmtFunctionExprSymbols_.find(ultimateSymbol) !=
+      stmtFunctionExprSymbols_.end()) {
+    context_.Say(name.source,
+        "Variable '%s' in STATEMENT FUNCTION expression cannot be in a "
+        "%s clause"_err_en_US,
+        name.ToString(), clauseName.str());
+  }
 }
 
 void OmpAttributeVisitor::CheckSourceLabel(const parser::Label &label) {
diff --git a/flang/lib/Semantics/semantics.cpp b/flang/lib/Semantics/semantics.cpp
index f7a277d1b414f6..2f1b9c139396a8 100644
--- a/flang/lib/Semantics/semantics.cpp
+++ b/flang/lib/Semantics/semantics.cpp
@@ -641,8 +641,8 @@ bool Semantics::Perform() {
       CanonicalizeAcc(context_.messages(), program_) &&
       CanonicalizeOmp(context_.messages(), program_) &&
       CanonicalizeCUDA(program_) &&
-      CanonicalizeDirectives(context_.messages(), program_) &&
       PerformStatementSemantics(context_, program_) &&
+      CanonicalizeDirectives(context_.messages(), program_) &&
       ModFileWriter{context_}
           .set_hermeticModuleFileOutput(hermeticModuleFileOutput_)
           .WriteAll();
diff --git a/flang/test/Semantics/OpenMP/private03.f90 b/flang/test/Semantics/OpenMP/private03.f90
new file mode 100644
index 00000000000000..3ce9cf81bb73a5
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/private03.f90
@@ -0,0 +1,39 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 4.5
+! Variables that appear in expressions for statement function definitions
+! may not appear in private, firstprivate or lastprivate clauses.
+
+subroutine stmt_function(temp)
+
+  integer :: i, p, q, r
+  real :: c, f, s, v, t(10)
+  real, intent(in) :: temp
+
+  c(temp) = p * (temp - q) / r
+  f(temp) = q + (temp * r/p)
+  v(temp) = c(temp) + f(temp)/2 - s
+
+  p = 5
+  q = 32
+  r = 9
+
+  !ERROR: Variable 'p' in STATEMENT FUNCTION expression cannot be in a PRIVATE clause
+  !$omp parallel private(p)
+  s = c(temp)
+  !$omp end parallel
+
+  !ERROR: Variable 's' in STATEMENT FUNCTION expression cannot be in a FIRSTPRIVATE clause
+  !$omp parallel firstprivate(s)
+  s = s + f(temp)
+  !$omp end parallel
+
+  !ERROR: Variable 's' in STATEMENT FUNCTION expression cannot be in a LASTPRIVATE clause
+  !$omp parallel do lastprivate(s, t)
+  do i = 1, 10
+  t(i) = v(temp) + i - s
+  end do
+  !$omp end parallel do
+
+  print *, t
+
+end subroutine stmt_function

>From 999cdd263ab71ca5c5e16bef44c3dd3aa5edde4c Mon Sep 17 00:00:00 2001
From: Tom Eccles <tom.eccles at arm.com>
Date: Thu, 29 Aug 2024 12:59:26 +0000
Subject: [PATCH 2/2] Empty commit

To re-trigger CI because of a spurious failure checking out the branch