Avoid unevaluated implicit private (#92055)

For every variable used under `#pragma omp task` directive
(`DeclRefExpr`) an ImplicitPrivateVariable is created in the AST, if
`private` or `shared` clauses are not present. If the variable has the
property of `non_odr_use_unevaluated` e.g. for statements which use
`sizeof( i )` `i` will have `non_odr_use_unevaluated` . In such cases
CodeGen was asserting by avoiding emitting of LLVM IR for such
variables. To prevent this assertion this checkin avoids adding the
ImplicitPrivateVariable for variables with `non_odr_use_unevaluated`.

---------

Authored-by: Sunil Kuravinakop <kuravina@pe28vega.us.cray.com>

clang/lib/Sema/SemaOpenMP.cpp

@@ -3757,7 +3757,8 @@ class DSAAttrChecker final : public StmtVisitor<DSAAttrChecker, void> {
   void VisitDeclRefExpr(DeclRefExpr *E) {
     if (TryCaptureCXXThisMembers || E->isTypeDependent() ||
         E->isValueDependent() || E->containsUnexpandedParameterPack() ||
-        E->isInstantiationDependent())
+        E->isInstantiationDependent() ||
+        E->isNonOdrUse() == clang::NOUR_Unevaluated)
       return;
     if (auto *VD = dyn_cast<VarDecl>(E->getDecl())) {
       // Check the datasharing rules for the expressions in the clauses.

clang/test/OpenMP/task_ast_print.cpp

@@ -5,6 +5,7 @@
 // RUN: %clang_cc1 -verify -Wno-vla -fopenmp-simd -ast-print %s | FileCheck %s
 // RUN: %clang_cc1 -fopenmp-simd -x c++ -std=c++11 -emit-pch -o %t %s
 // RUN: %clang_cc1 -fopenmp-simd -std=c++11 -include-pch %t -verify -Wno-vla %s -ast-print | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fopenmp -ast-dump  %s | FileCheck %s --check-prefix=DUMP
 // expected-no-diagnostics
 
 #ifndef HEADER
@@ -208,4 +209,44 @@ int main(int argc, char **argv) {
 extern template int S<int>::TS;
 extern template long S<long>::TS;
 
+// DUMP-LABEL:  FunctionDecl {{.*}} implicit_firstprivate
+void
+implicit_firstprivate() {
+
+#pragma omp parallel num_threads(1)
+  {
+    int i = 0;
+    // DUMP: OMPTaskDirective 
+    // DUMP-NEXT: OMPFirstprivateClause
+    // DUMP-NOT: DeclRefExpr {{.+}} 'i' {{.+}} non_odr_use_unevaluated
+    // DUMP: DeclRefExpr {{.+}} 'i' 'int' refers_to_enclosing_variable_or_capture
+    // DUMP: CapturedStmt
+    // DUMP: BinaryOperator {{.+}} 'int' lvalue '='
+    // DUMP-NEXT: DeclRefExpr {{.+}} 'j' 'int'
+    // DUMP: DeclRefExpr {{.+}} 'i' {{.+}} non_odr_use_unevaluated
+    #pragma omp task
+    {
+	int j = sizeof(i);
+	j = i;
+    }
+  }
+}
+
+// DUMP-LABEL:  FunctionDecl {{.*}} no_implicit_firstprivate
+void
+no_implicit_firstprivate() {
+
+#pragma omp parallel num_threads(1)
+  {
+    int i = 0;
+    // DUMP: OMPTaskDirective
+    // DUMP-NEXT: CapturedStmt
+    // DUMP: DeclRefExpr {{.+}} 'i' {{.+}} non_odr_use_unevaluated refers_to_enclosing_variable_or_capture
+    #pragma omp task
+    {
+	int j = sizeof(i);
+    }
+  }
+}
+
 #endif