[OPENMP]Add support for analysis of if clauses.

Summary:
Added support for analysis of if clauses in the OpenMP directives to be
able to check for the use of uninitialized variables.

Reviewers: NoQ

Subscribers: guansong, jfb, jdoerfert, caomhin, kkwli0, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64646

llvm-svn: 366068

Author: alexey-bataev

clang/include/clang/AST/OpenMPClause.h

@@ -501,11 +501,10 @@ class OMPIfClause : public OMPClause, public OMPClauseWithPreInit {
     return const_child_range(&Condition, &Condition + 1);
   }
 
-  child_range used_children() {
-    return child_range(child_iterator(), child_iterator());
-  }
+  child_range used_children();
   const_child_range used_children() const {
-    return const_child_range(const_child_iterator(), const_child_iterator());
+    auto Children = const_cast<OMPIfClause *>(this)->used_children();
+    return const_child_range(Children.begin(), Children.end());
   }
 
   static bool classof(const OMPClause *T) {

clang/lib/AST/OpenMPClause.cpp

@@ -209,6 +209,25 @@ const OMPClauseWithPostUpdate *OMPClauseWithPostUpdate::get(const OMPClause *C)
   return nullptr;
 }
 
+/// Gets the address of the original, non-captured, expression used in the
+/// clause as the preinitializer.
+static Stmt **getAddrOfExprAsWritten(Stmt *S) {
+  if (!S)
+    return nullptr;
+  if (auto *DS = dyn_cast<DeclStmt>(S)) {
+    assert(DS->isSingleDecl() && "Only single expression must be captured.");
+    if (auto *OED = dyn_cast<OMPCapturedExprDecl>(DS->getSingleDecl()))
+      return OED->getInitAddress();
+  }
+  return nullptr;
+}
+
+OMPClause::child_range OMPIfClause::used_children() {
+  if (Stmt **C = getAddrOfExprAsWritten(getPreInitStmt()))
+    return child_range(C, C + 1);
+  return child_range(&Condition, &Condition + 1);
+}
+
 OMPOrderedClause *OMPOrderedClause::Create(const ASTContext &C, Expr *Num,
                                            unsigned NumLoops,
                                            SourceLocation StartLoc,