Handle alignas(foo...) pack expansions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175875 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 88 insertions, 42 deletions

diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 1142e0dd2d..8e2bac6ed0 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -3315,27 +3315,28 @@ static void handleAlignedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
     return;
   }
 
-  // FIXME: The C++11 version of this attribute should error out when it is
-  //        used to specify a weaker alignment, rather than being silently
-  //        ignored. This constraint cannot be applied until we have seen
-  //        all the attributes which apply to the variable.
-
   if (Attr.getNumArgs() == 0) {
     D->addAttr(::new (S.Context) AlignedAttr(Attr.getRange(), S.Context,
                true, 0, Attr.getAttributeSpellingListIndex()));
     return;
   }
 
-  S.AddAlignedAttr(Attr.getRange(), D, Attr.getArg(0),
-                   Attr.getAttributeSpellingListIndex());
-}
+  Expr *E = Attr.getArg(0);
+  if (Attr.isPackExpansion() && !E->containsUnexpandedParameterPack()) {
+    S.Diag(Attr.getEllipsisLoc(),
+           diag::err_pack_expansion_without_parameter_packs);
+    return;
+  }
 
-void Sema::AddAlignedAttr(SourceRange AttrRange, Decl *D, Expr *E,
-                          unsigned SpellingListIndex) {
-  // FIXME: Handle pack-expansions here.
-  if (DiagnoseUnexpandedParameterPack(E))
+  if (!Attr.isPackExpansion() && S.DiagnoseUnexpandedParameterPack(E))
     return;
 
+  S.AddAlignedAttr(Attr.getRange(), D, E, Attr.getAttributeSpellingListIndex(),
+                   Attr.isPackExpansion());
+}
+
+void Sema::AddAlignedAttr(SourceRange AttrRange, Decl *D, Expr *E,
+                          unsigned SpellingListIndex, bool IsPackExpansion) {
   AlignedAttr TmpAttr(AttrRange, Context, true, E, SpellingListIndex);
   SourceLocation AttrLoc = AttrRange.getBegin();
 
@@ -3379,7 +3380,9 @@ void Sema::AddAlignedAttr(SourceRange AttrRange, Decl *D, Expr *E,
 
   if (E->isTypeDependent() || E->isValueDependent()) {
     // Save dependent expressions in the AST to be instantiated.
-    D->addAttr(::new (Context) AlignedAttr(TmpAttr));
+    AlignedAttr *AA = ::new (Context) AlignedAttr(TmpAttr);
+    AA->setPackExpansion(IsPackExpansion);
+    D->addAttr(AA);
     return;
   }
 
@@ -3414,17 +3417,20 @@ void Sema::AddAlignedAttr(SourceRange AttrRange, Decl *D, Expr *E,
     }
   }
 
-  D->addAttr(::new (Context) AlignedAttr(AttrRange, Context, true,
-                                         ICE.take(), SpellingListIndex));
+  AlignedAttr *AA = ::new (Context) AlignedAttr(AttrRange, Context, true,
+                                                ICE.take(), SpellingListIndex);
+  AA->setPackExpansion(IsPackExpansion);
+  D->addAttr(AA);
 }
 
 void Sema::AddAlignedAttr(SourceRange AttrRange, Decl *D, TypeSourceInfo *TS,
-                          unsigned SpellingListIndex) {
+                          unsigned SpellingListIndex, bool IsPackExpansion) {
   // FIXME: Cache the number on the Attr object if non-dependent?
   // FIXME: Perform checking of type validity
-  D->addAttr(::new (Context) AlignedAttr(AttrRange, Context, false, TS,
-                                         SpellingListIndex));
-  return;
+  AlignedAttr *AA = ::new (Context) AlignedAttr(AttrRange, Context, false, TS,
+                                                SpellingListIndex);
+  AA->setPackExpansion(IsPackExpansion);
+  D->addAttr(AA);
 }
 
 void Sema::CheckAlignasUnderalignment(Decl *D) {
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index defa968475..a829070b2f 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -60,6 +60,64 @@ bool TemplateDeclInstantiator::SubstQualifier(const TagDecl *OldDecl,
 // Include attribute instantiation code.
 #include "clang/Sema/AttrTemplateInstantiate.inc"
 
+static void instantiateDependentAlignedAttr(
+    Sema &S, const MultiLevelTemplateArgumentList &TemplateArgs,
+    const AlignedAttr *Aligned, Decl *New, bool IsPackExpansion) {
+  if (Aligned->isAlignmentExpr()) {
+    // The alignment expression is a constant expression.
+    EnterExpressionEvaluationContext Unevaluated(S, Sema::ConstantEvaluated);
+    ExprResult Result = S.SubstExpr(Aligned->getAlignmentExpr(), TemplateArgs);
+    if (!Result.isInvalid())
+      S.AddAlignedAttr(Aligned->getLocation(), New, Result.takeAs<Expr>(),
+                       Aligned->getSpellingListIndex(), IsPackExpansion);
+  } else {
+    TypeSourceInfo *Result = S.SubstType(Aligned->getAlignmentType(),
+                                         TemplateArgs, Aligned->getLocation(),
+                                         DeclarationName());
+    if (Result)
+      S.AddAlignedAttr(Aligned->getLocation(), New, Result,
+                       Aligned->getSpellingListIndex(), IsPackExpansion);
+  }
+}
+
+static void instantiateDependentAlignedAttr(
+    Sema &S, const MultiLevelTemplateArgumentList &TemplateArgs,
+    const AlignedAttr *Aligned, Decl *New) {
+  if (!Aligned->isPackExpansion()) {
+    instantiateDependentAlignedAttr(S, TemplateArgs, Aligned, New, false);
+    return;
+  }
+
+  SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+  if (Aligned->isAlignmentExpr())
+    S.collectUnexpandedParameterPacks(Aligned->getAlignmentExpr(),
+                                      Unexpanded);
+  else
+    S.collectUnexpandedParameterPacks(Aligned->getAlignmentType()->getTypeLoc(),
+                                      Unexpanded);
+  assert(!Unexpanded.empty() && "Pack expansion without parameter packs?");
+
+  // Determine whether we can expand this attribute pack yet.
+  bool Expand = true, RetainExpansion = false;
+  Optional<unsigned> NumExpansions;
+  // FIXME: Use the actual location of the ellipsis.
+  SourceLocation EllipsisLoc = Aligned->getLocation();
+  if (S.CheckParameterPacksForExpansion(EllipsisLoc, Aligned->getRange(),
+                                        Unexpanded, TemplateArgs, Expand,
+                                        RetainExpansion, NumExpansions))
+    return;
+
+  if (!Expand) {
+    Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(S, -1);
+    instantiateDependentAlignedAttr(S, TemplateArgs, Aligned, New, true);
+  } else {
+    for (unsigned I = 0; I != *NumExpansions; ++I) {
+      Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(S, I);
+      instantiateDependentAlignedAttr(S, TemplateArgs, Aligned, New, false);
+    }
+  }
+}
+
 void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
                             const Decl *Tmpl, Decl *New,
                             LateInstantiatedAttrVec *LateAttrs,
@@ -69,31 +127,13 @@ void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
     const Attr *TmplAttr = *i;
 
     // FIXME: This should be generalized to more than just the AlignedAttr.
-    if (const AlignedAttr *Aligned = dyn_cast<AlignedAttr>(TmplAttr)) {
-      if (Aligned->isAlignmentDependent()) {
-        if (Aligned->isAlignmentExpr()) {
-          // The alignment expression is a constant expression.
-          EnterExpressionEvaluationContext Unevaluated(*this,
-                                                       Sema::ConstantEvaluated);
-
-          ExprResult Result = SubstExpr(Aligned->getAlignmentExpr(),
-                                        TemplateArgs);
-          if (!Result.isInvalid())
-            AddAlignedAttr(Aligned->getLocation(), New, Result.takeAs<Expr>(),
-                           Aligned->getSpellingListIndex());
-        } else {
-          TypeSourceInfo *Result = SubstType(Aligned->getAlignmentType(),
-                                             TemplateArgs,
-                                             Aligned->getLocation(),
-                                             DeclarationName());
-          if (Result)
-            AddAlignedAttr(Aligned->getLocation(), New, Result,
-                           Aligned->getSpellingListIndex());
-        }
-        continue;
-      }
+    const AlignedAttr *Aligned = dyn_cast<AlignedAttr>(TmplAttr);
+    if (Aligned && Aligned->isAlignmentDependent()) {
+      instantiateDependentAlignedAttr(*this, TemplateArgs, Aligned, New);
+      continue;
     }
 
+    assert(!TmplAttr->isPackExpansion());
     if (TmplAttr->isLateParsed() && LateAttrs) {
       // Late parsed attributes must be instantiated and attached after the
       // enclosing class has been instantiated.  See Sema::InstantiateClass.