Support for OpenMP 5.0 sec 2.12.7 - Declare Target initializer expressions

[RitanyaB]

Summary

Initial support for OpenMP 5.0 declare target "as if" behavior for "initializer expressions".
If a variable with static storage duration or a function (except lambda for C++) is referenced in the initializer expression list of a variable with static storage duration that appears as a list item in a to clause on a declare target directive then the name of the referenced variable or function is treated as if it had appeared in a to clause on a declare target directive.

[ABataev]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

It has nothing to do with parsing, sema analysis. Make it part of Sema::checkDeclIsAllowedInOpenMPTarget

2107 ↗

(On Diff #506554)

Try to avoid recursion here

[RitanyaB]

clang/lib/Parse/ParseDecl.cpp

2107 ↗

(On Diff #506554)

Consider the following example-

static int var1 = 10; 
static int *var2 = &var1;
#pragma omp declare target
int **ptr1=&var2;
#pragma omp end declare target

In this case, by default ptr1 gets OMPDeclareTargetDeclAttr and the function mentioned above (ParseImplicitDeclareTargetAttr) would add OMPDeclareTargetDeclAttr to var2. But, in order to add OMPDeclareTargetDeclAttr to var1, recursion would be required.

[ABataev]

clang/lib/Parse/ParseDecl.cpp

2107 ↗

(On Diff #506554)

I do not ask to remove it, but use extra memory (SamllVector) to save the decls, requiring analysis, and iterate through this vector.

[RitanyaB]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

The Declaration in Sema::checkDeclIsAllowedInOpenMPTarget is incomplete.

VarDecl 0x1582b278 <test3.c:6:1, col:7> col:7 ptr1 'int **'
`-OMPDeclareTargetDeclAttr 0x1582b2e0 <line:5:21> Implicit MT_To DT_Any 1
  `-<<<NULL>>>

At this point, I do not have access to the initializer expression. Any suggestions?

[ABataev]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

The try to do it ActOnOpenMPDeclareTargetName

[RitanyaB]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

In the absence of a declare target clause, this function is not invoked (in the examples used above, the function is never called). Do you have any suggestions?

[ABataev]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

For such decls use checkDeclIsAllowedInOpenMPTarget

[RitanyaB]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

As mentioned in my previous comment, the Decl in checkDeclIsAllowedInOpenMPTarget is not complete and I don't have access to the initializer expression hence I am unable to move my functionality into checkDeclIsAllowedInOpenMPTarget.
After ParseDeclarationAfterDeclaratorAndAttributes returns, the Decl is complete and I can process it accordingly.

[ABataev]

clang/lib/Parse/ParseDecl.cpp

2093–2115 ↗

(On Diff #506554)

For decls, explicitly marked as DeclareTarget, use The try to do it ActOnOpenMPDeclareTargetName. For decls, referenced in the initializers, use checkDeclIsAllowedInOpenMPTarget.

[RitanyaB]

Adding the support in SemaOpenMP.cpp.

[ABataev]

clang/lib/Sema/SemaDecl.cpp

14473–14474

if (auto *VD = dyn_cast_or_null<VarDecl>(D); LangOpts.OpenMP && VD && VD->hasAttr<OMPDeclareTargetDeclAttr>() && VD->hasGlobalStorage())

clang/lib/Sema/SemaOpenMP.cpp

23104

static void addOMP...

23105

SmallVectorImpl<Decl *> &DeclVector

23106–23113

if (!DeclRef)

return;

if (auto *VD = dyn_cast_or_null<VarDecl>(DeclRef->getDecl()) {

DeclVar->addAttr(TargetDecl->getAttr<OMPDeclareTargetDeclAttr>());
DeclVector.push_back(DeclVar);

}

23116–23127

Use StmtVisitor to implement this correctly.

23133

100 is to much, use either default value SmallVector<Decl *> DeclVector; or smaller value (4 should be enough)

23135

while (!DeclVector.empty())

23136–23137

Decl *D = DeclVector.pop_back_val();

23138–23139

Use dyn_cast instead of isa/cast

[ABataev]

clang/lib/Sema/SemaDecl.cpp

14473

В is already checked that is not nullptr, so just a dyn_cast should be enough

clang/lib/Sema/SemaOpenMP.cpp

23106–23107

Why public?

23110

const auto *VD

23111

Use VD instead of this and drop const

23112–23113

Drop this and extra parens

23119–23122

Just Visit(*it)?

[RitanyaB]

clang/lib/Sema/SemaOpenMP.cpp

23106–23107

As the data members are accessed from outside the class (in ActOnOpenMPImplicitDeclareTarget function), I have made them public.

23119–23122

Or I can call VisitDeclRefExpr directly. Would that be more suitable?

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

23106–23107

If you need them, implement getters for them and make them private.

23118–23119

Why just a regular Visit does not work here? Plus, isa + dyn_cast is weird.

[ABataev]

clang/include/clang/Sema/Sema.h

11332

Do I understand correctly, that the variable itself is marked explicitly, but the initializer shall be marked implicitly? If so, please fix the function name

clang/lib/Sema/SemaOpenMP.cpp

23109–23110

Remove this->, where not required.

23111

1. Wrong function name format.
2. Do you really need to make it public? Hide as much as possible.

23114

Same, as for Push

23138–23152

Better to hide this in GlobalDeclRefChecker

[ABataev]

clang/lib/Sema/SemaDecl.cpp

14475–14477

Remove braces

clang/lib/Sema/SemaOpenMP.cpp

23103

Please, add comments, describing the class and its functionality

23107

setTargetDecl

23108

1. checkDeclVector
2. const member function

23110

const member function

23116

Remove this->

23125

1. Better to make it static member function.
2. Follow the rules for function names.

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

23121–23122

for (const Expr *Child : Ex->children())

23138–23143

Shall just something like this work here:

if (Ex)
  Visit(Ex);

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

23136

Better to expand auto here

23137

Formatting?

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

23106

Use just a StmtVisitor, if you still dropping const modifier.

23114

remove const_cast

23131

You don't need to use dyn_cast here, use just cast

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

23127

Fix the strange symbol in the comment

23129

Function names should be verb phrases (as they represent actions), and command-like function should be imperative. (https://llvm.org/docs/CodingStandards.html#name-types-functions-variables-and-enumerators-properly)

[ABataev]

LG

[DavidSpickett]

clang/lib/Sema/SemaOpenMP.cpp

23148

FYI I fixed an unused var warning here: https://github.com/llvm/llvm-project/commit/f3ca99a87c566fb5e910071f4cbb474ddb4e7f37

Potentially you could pass the result of the cast into declareTargetInitializer but I don't know enough about the code to change that too.

clang/include/clang/Sema/Sema.h

public:
   void ActOnOpenMPDeclareTargetName(NamedDecl *ND, SourceLocation Loc,
                                     OMPDeclareTargetDeclAttr::MapTypeTy MT,
                                     DeclareTargetContextInfo &DTCI);
 
   /// Check declaration inside target region.
   void
   checkDeclIsAllowedInOpenMPTarget(Expr *E, Decl *D,
                                    SourceLocation IdLoc = SourceLocation());
+
+  /// Adds OMPDeclareTargetDeclAttr to referenced variables in declare target
+  /// directive.
+  void ActOnOpenMPDeclareTargetInitializer(Decl *D);
+
   /// Finishes analysis of the deferred functions calls that may be declared as
   /// host/nohost during device/host compilation.
   void finalizeOpenMPDelayedAnalysis(const FunctionDecl *Caller,
                                      const FunctionDecl *Callee,
                                      SourceLocation Loc);
 
   /// Return true if currently in OpenMP task with untied clause context.
   bool isInOpenMPTaskUntiedContext() const;

clang/lib/Sema/SemaDecl.cpp

Sema::DeclGroupPtrTy Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
   DeclaratorDecl *FirstDeclaratorInGroup = nullptr;
   DecompositionDecl *FirstDecompDeclaratorInGroup = nullptr;
   bool DiagnosedMultipleDecomps = false;
   DeclaratorDecl *FirstNonDeducedAutoInGroup = nullptr;
   bool DiagnosedNonDeducedAuto = false;
 
   for (unsigned i = 0, e = Group.size(); i != e; ++i) {
     if (Decl *D = Group[i]) {
+      // Check if the Decl has been declared in '#pragma omp declare target'
+      // directive and has static storage duration.
+      if (auto *VD = dyn_cast<VarDecl>(D);
+          LangOpts.OpenMP && VD && VD->hasAttr<OMPDeclareTargetDeclAttr>() &&
+          VD->hasGlobalStorage())
+        ActOnOpenMPDeclareTargetInitializer(D);
       // For declarators, there are some additional syntactic-ish checks we need
       // to perform.
       if (auto *DD = dyn_cast<DeclaratorDecl>(D)) {
         if (!FirstDeclaratorInGroup)
           FirstDeclaratorInGroup = DD;
         if (!FirstDecompDeclaratorInGroup)
           FirstDecompDeclaratorInGroup = dyn_cast<DecompositionDecl>(D);
         if (!FirstNonDeducedAutoInGroup && DS.hasAutoTypeSpec() &&
             !hasDeducedAuto(DD))

clang/lib/Sema/SemaOpenMP.cpp

if (!E && isInOpenMPDeclareTargetContext()) {
       return;
     }
   }
   if (!E)
     return;
   checkDeclInTargetContext(E->getExprLoc(), E->getSourceRange(), *this, D);
 }
 
+/// This class visits every VarDecl that the initializer references and adds 
+/// OMPDeclareTargetDeclAttr to each of them.
+class GlobalDeclRefChecker final
+    : public ConstStmtVisitor<GlobalDeclRefChecker> {
+  SmallVector<VarDecl *> DeclVector;
+  Attr *A;
+
+public:
+  /// A StmtVisitor class function that visits all DeclRefExpr and adds 
+  /// OMPDeclareTargetDeclAttr to them.
+  void VisitDeclRefExpr(const DeclRefExpr *Node) {
+    if (auto *VD = const_cast<VarDecl *>(dyn_cast<VarDecl>(Node->getDecl()))) {
+      VD->addAttr(A);
+      DeclVector.push_back(VD);
+    }
+  }
+  /// A function that iterates across each of the Expr's children.
+  void VisitExpr(const Expr *Ex) {
+    for (auto *Child : Ex->children()) {
+      Visit(Child);
+    }
+  } 
+  /// A function that keeps a record of all the Decls that are variables, has 
+  /// OMPDeclareTargetDeclAttr, and has global storage in the DeclVector. Pop 
+  /// each Decl one at a time and use the inherited Visit functions!to look for 
+  /// DeclRefExpr.
+  void declTargetInitializer(Decl *TD) {
+    A = TD->getAttr<OMPDeclareTargetDeclAttr>();
+    DeclVector.push_back(dyn_cast<VarDecl>(TD));
+    while (!DeclVector.empty()) {
+      VarDecl *TargetVarDecl = DeclVector.pop_back_val();
+      if (TargetVarDecl->hasAttr<OMPDeclareTargetDeclAttr>() &&
+          TargetVarDecl->hasInit() && TargetVarDecl->hasGlobalStorage()) {
+        if (const Expr *Ex = TargetVarDecl->getInit()) 
+          Visit(Ex);
+      }
+    }
+  }
+};
+
+/// Adding OMPDeclareTargetDeclAttr to variables with static storage
+/// duration that are referenced in the initializer expression list of
+/// variables with static storage duration in declare target directive.
+void Sema::ActOnOpenMPDeclareTargetInitializer(Decl *TargetDecl) {
+  GlobalDeclRefChecker Checker;
+  if (auto *TargetVarDecl = dyn_cast_or_null<VarDecl>(TargetDecl))
+    Checker.declTargetInitializer(TargetDecl);
+}
+
 OMPClause *Sema::ActOnOpenMPToClause(
     ArrayRef<OpenMPMotionModifierKind> MotionModifiers,
     ArrayRef<SourceLocation> MotionModifiersLoc,
     CXXScopeSpec &MapperIdScopeSpec, DeclarationNameInfo &MapperId,
     SourceLocation ColonLoc, ArrayRef<Expr *> VarList,
     const OMPVarListLocTy &Locs, ArrayRef<Expr *> UnresolvedMappers) {
   OpenMPMotionModifierKind Modifiers[] = {OMPC_MOTION_MODIFIER_unknown,
                                           OMPC_MOTION_MODIFIER_unknown};
   SourceLocation ModifiersLoc[NumberOfOMPMotionModifiers];

clang/test/OpenMP/declare_target_messages.cpp

 void any7() {device();} // host5-error {{function with 'device_type(nohost)' is not available on host}}
 void any8() {any2();}
 
 int MultiDevTy;
 #pragma omp declare target to(MultiDevTy) device_type(any)    // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} omp52-error {{unexpected 'to' clause, use 'enter' instead}} omp52-error {{expected at least one 'enter', 'link' or 'indirect' clause}}
 #pragma omp declare target to(MultiDevTy) device_type(host)   // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} omp5-error {{'device_type(host)' does not match previously specified 'device_type(any)' for the same declaration}} omp51-error {{'device_type(host)' does not match previously specified 'device_type(any)' for the same declaration}} omp52-error {{unexpected 'to' clause, use 'enter' instead}} omp52-error {{expected at least one 'enter', 'link' or 'indirect' clause}}
 #pragma omp declare target to(MultiDevTy) device_type(nohost) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} omp5-error {{'device_type(nohost)' does not match previously specified 'device_type(any)' for the same declaration}} // omp51-error {{'device_type(nohost)' does not match previously specified 'device_type(any)' for the same declaration}} omp52-error {{unexpected 'to' clause, use 'enter' instead}} omp52-error {{expected at least one 'enter', 'link' or 'indirect' clause}}
 
+static int variable = 100;  //expected-warning {{declaration is not declared in any declare target region}}
+static float variable1 = 200;
+static float variable2 = variable1;  //expected-warning {{declaration is not declared in any declare target region}}
+
+static int var = 1;  //expected-warning {{declaration is not declared in any declare target region}}
+
+static int var1 = 10;
+static int *var2 = &var1;
+static int **ptr1 = &var2;  //expected-warning {{declaration is not declared in any declare target region}}
+
+int arr[2] = {1,2};
+int (*arrptr)[2] = &arr;  //expected-warning {{declaration is not declared in any declare target region}}
+
+class declare{
+  public: int x;
+          void print();
+};
+declare obj1;
+declare *obj2 = &obj1;  //expected-warning {{declaration is not declared in any declare target region}}
+
+struct target{
+  int x;
+  void print();
+};
+static target S;  //expected-warning {{declaration is not declared in any declare target region}}
+
+#pragma omp declare target
+int target_var = variable;  //expected-note {{used here}}
+float target_var1 = variable2;  //expected-note {{used here}}
+int *ptr = &var;  //expected-note {{used here}}
+int ***ptr2 = &ptr1;  //expected-note {{used here}}
+int (**ptr3)[2] = &arrptr;  //expected-note {{used here}}
+declare **obj3 = &obj2;  //expected-note {{used here}}
+target *S1 = &S; //expected-note {{used here}}
+#pragma omp end declare target
+
 #if TESTENDINC
 #include "unterminated_declare_target_include.h"
 #elif TESTEND
 // expected-warning@+1 {{expected '#pragma omp end declare target' at end of file to match '#pragma omp declare target'}}
 #pragma omp declare target
 #else
 // expected-warning@+1 {{expected '#pragma omp end declare target' at end of file to match '#pragma omp begin declare target'}}
 #pragma omp begin declare target
 #endif

clang/test/OpenMP/declare_target_variables_ast_print.cpp

+// RUN: %clang_cc1 -w -verify -fopenmp -I %S/Inputs -ast-print %s | FileCheck %s --check-prefix=CHECK
+// expected-no-diagnostics
+
+static int variable = 100;
+static float variable1 = 200;
+static float variable2 = variable1;
+
+static int var = 1;
+
+static int var1 = 10;
+static int *var2 = &var1;
+static int **ptr1 = &var2;
+
+int arr[2] = {1,2};
+int (*arrptr)[2] = &arr;
+
+class declare{
+  public: int x;
+          void print();
+};
+declare obj1;
+declare *obj2 = &obj1;
+
+struct target{
+  int x;
+  void print();
+};
+static target S;
+
+#pragma omp declare target
+int target_var = variable;
+float target_var1 = variable2;
+int *ptr = &var;
+int ***ptr2 = &ptr1;
+int (**ptr3)[2] = &arrptr;
+declare **obj3 = &obj2;
+target *S1 = &S;
+#pragma omp end declare target
+// CHECK: #pragma omp declare target
+// CHECK-NEXT: static int variable = 100;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: static float variable1 = 200;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: static float variable2 = variable1;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK: #pragma omp declare target
+// CHECK-NEXT: static int var = 1;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: static int var1 = 10;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: static int *var2 = &var1;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: static int **ptr1 = &var2;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: int arr[2] = {1, 2};
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: int (*arrptr)[2] = &arr;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK-NEXT: class declare {
+// CHECK-NEXT: public:
+// CHECK-NEXT:  int x;
+// CHECK-NEXT:  void print();
+// CHECK-NEXT: };
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: declare obj1;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: declare *obj2 = &obj1;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK-NEXT: struct target {
+// CHECK-NEXT:  int x;
+// CHECK-NEXT:  void print();
+// CHECK-NEXT: };
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: static target S;
+// CHECK-NEXT: #pragma omp end declare target
+
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: int target_var = variable;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: float target_var1 = variable2;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: int *ptr = &var;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: int ***ptr2 = &ptr1;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: int (**ptr3)[2] = &arrptr;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: declare **obj3 = &obj2;
+// CHECK-NEXT: #pragma omp end declare target
+// CHECK-NEXT: #pragma omp declare target
+// CHECK-NEXT: target *S1 = &S;
+// CHECK-NEXT: #pragma omp end declare target
+

clang/test/OpenMP/nvptx_target_exceptions_messages.cpp

 
 int foobar3();
 int (*C)() = &foobar3; // expected-warning {{declaration is not declared in any declare target region}}
                        // host-warning@-1 {{declaration is not declared in any declare target region}}
 #pragma omp declare target
 int (*D)() = C; // expected-note {{used here}}
                 // host-note@-1 {{used here}}
 #pragma omp end declare target
-int foobar3() { throw 1; }
+int foobar3() { throw 1; } // expected-error {{cannot use 'throw' with exceptions disabled}}
 
 // Check no infinite recursion in deferred diagnostic emitter.
 long E = (long)&E;
 
 #endif // HEADER