AST: alignof might be dependent because of alignment attributes

Dependent alignment attributes should make an alignof expression
dependent as well.

llvm-svn: 226156

3 files changed, 46 insertions, 12 deletions

diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
index c410f2358bc..96131d2b932 100644
--- a/clang/include/clang/AST/Expr.h
+++ b/clang/include/clang/AST/Expr.h
@@ -1997,18 +1997,7 @@ public:
 
   UnaryExprOrTypeTraitExpr(UnaryExprOrTypeTrait ExprKind, Expr *E,
                            QualType resultType, SourceLocation op,
-                           SourceLocation rp) :
-      Expr(UnaryExprOrTypeTraitExprClass, resultType, VK_RValue, OK_Ordinary,
-           false, // Never type-dependent (C++ [temp.dep.expr]p3).
-           // Value-dependent if the argument is type-dependent.
-           E->isTypeDependent(),
-           E->isInstantiationDependent(),
-           E->containsUnexpandedParameterPack()),
-      OpLoc(op), RParenLoc(rp) {
-    UnaryExprOrTypeTraitExprBits.Kind = ExprKind;
-    UnaryExprOrTypeTraitExprBits.IsType = false;
-    Argument.Ex = E;
-  }
+                           SourceLocation rp);
 
   /// \brief Construct an empty sizeof/alignof expression.
   explicit UnaryExprOrTypeTraitExpr(EmptyShell Empty)
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 712de5056e8..e7b7f20c120 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1360,6 +1360,44 @@ IdentifierInfo *OffsetOfExpr::OffsetOfNode::getFieldName() const {
   return reinterpret_cast<IdentifierInfo *> (Data & ~(uintptr_t)Mask);
 }
 
+UnaryExprOrTypeTraitExpr::UnaryExprOrTypeTraitExpr(
+    UnaryExprOrTypeTrait ExprKind, Expr *E, QualType resultType,
+    SourceLocation op, SourceLocation rp)
+    : Expr(UnaryExprOrTypeTraitExprClass, resultType, VK_RValue, OK_Ordinary,
+           false, // Never type-dependent (C++ [temp.dep.expr]p3).
+           // Value-dependent if the argument is type-dependent.
+           E->isTypeDependent(), E->isInstantiationDependent(),
+           E->containsUnexpandedParameterPack()),
+      OpLoc(op), RParenLoc(rp) {
+  UnaryExprOrTypeTraitExprBits.Kind = ExprKind;
+  UnaryExprOrTypeTraitExprBits.IsType = false;
+  Argument.Ex = E;
+
+  // Check to see if we are in the situation where alignof(decl) should be
+  // dependent because decl's alignment is dependent.
+  if (ExprKind == UETT_AlignOf) {
+    if (!isValueDependent() || !isInstantiationDependent()) {
+      E = E->IgnoreParens();
+
+      const ValueDecl *D = nullptr;
+      if (const auto *DRE = dyn_cast<DeclRefExpr>(E))
+        D = DRE->getDecl();
+      else if (const auto *ME = dyn_cast<MemberExpr>(E))
+        D = ME->getMemberDecl();
+
+      if (D) {
+        for (const auto *I : D->specific_attrs<AlignedAttr>()) {
+          if (I->isAlignmentDependent()) {
+            setValueDependent(true);
+            setInstantiationDependent(true);
+            break;
+          }
+        }
+      }
+    }
+  }
+}
+
 MemberExpr *MemberExpr::Create(const ASTContext &C, Expr *base, bool isarrow,
                                NestedNameSpecifierLoc QualifierLoc,
                                SourceLocation TemplateKWLoc,
diff --git a/clang/test/SemaCXX/alignof.cpp b/clang/test/SemaCXX/alignof.cpp
index 011f459abdf..f51146ccd3c 100644
--- a/clang/test/SemaCXX/alignof.cpp
+++ b/clang/test/SemaCXX/alignof.cpp
@@ -77,3 +77,10 @@ namespace alignof_array_expr {
   // ok, does not complete type of S<-1>::a
   static_assert(alignof(S<-1>::a) == alignof(int), ""); // expected-warning {{GNU extension}}
 }
+
+template <typename T> void n(T) {
+  alignas(T) int T1;
+  char k[__alignof__(T1)];
+  static_assert(sizeof(k) == alignof(long long), "");
+}
+template void n(long long);