r226653 - AST: Don't ignore alignas on EnumDecls when calculating alignment

[David Majnemer]

Author: majnemer
Date: Wed Jan 21 04:54:38 2015
New Revision: 226653

URL: http://llvm.org/viewvc/llvm-project?rev=226653&view=rev
Log:
AST: Don't ignore alignas on EnumDecls when calculating alignment

We didn't consider any alignment attributes on an EnumDecl when
calculating alignment.

While we are here, ignore alignment specifications on typedef types if
one is used as the underlying type.  Otherwise, weird things happen:

enum Y : int;
Y y;

typedef int __attribute__((aligned(64))) u;
enum Y : u {};

What is the alignment of 'Y'?  It would be more consistent with the
overall design of enums with fixed underlying types to consider the
underlying type's UnqualifiedDesugaredType.

This fixes PR22279.

Modified:
    cfe/trunk/lib/AST/ASTContext.cpp
    cfe/trunk/lib/Sema/SemaDeclAttr.cpp
    cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
    cfe/trunk/test/Sema/align-x86.c

Modified: cfe/trunk/lib/AST/ASTContext.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTContext.cpp?rev=226653&r1=226652&r2=226653&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ASTContext.cpp (original)
+++ cfe/trunk/lib/AST/ASTContext.cpp Wed Jan 21 04:54:38 2015
@@ -1670,8 +1670,16 @@ TypeInfo ASTContext::getTypeInfoImpl(con
       break;
     }
 
-    if (const EnumType *ET = dyn_cast<EnumType>(TT))
-      return getTypeInfo(ET->getDecl()->getIntegerType());
+    if (const EnumType *ET = dyn_cast<EnumType>(TT)) {
+      const EnumDecl *ED = ET->getDecl();
+      TypeInfo Info =
+          getTypeInfo(ED->getIntegerType()->getUnqualifiedDesugaredType());
+      if (unsigned AttrAlign = ED->getMaxAlignment()) {
+        Info.Align = AttrAlign;
+        Info.AlignIsRequired = true;
+      }
+      return Info;
+    }
 
     const RecordType *RT = cast<RecordType>(TT);
     const ASTRecordLayout &Layout = getASTRecordLayout(RT->getDecl());
@@ -1786,6 +1794,8 @@ unsigned ASTContext::getPreferredTypeAli
   T = T->getBaseElementTypeUnsafe();
   if (const ComplexType *CT = T->getAs<ComplexType>())
     T = CT->getElementType().getTypePtr();
+  if (const EnumType *ET = T->getAs<EnumType>())
+    T = ET->getDecl()->getIntegerType().getTypePtr();
   if (T->isSpecificBuiltinType(BuiltinType::Double) ||
       T->isSpecificBuiltinType(BuiltinType::LongLong) ||
       T->isSpecificBuiltinType(BuiltinType::ULongLong))

Modified: cfe/trunk/lib/Sema/SemaDeclAttr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclAttr.cpp?rev=226653&r1=226652&r2=226653&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDeclAttr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDeclAttr.cpp Wed Jan 21 04:54:38 2015
@@ -2953,12 +2953,15 @@ void Sema::AddAlignedAttr(SourceRange At
 void Sema::CheckAlignasUnderalignment(Decl *D) {
   assert(D->hasAttrs() && "no attributes on decl");
 
-  QualType Ty;
-  if (ValueDecl *VD = dyn_cast<ValueDecl>(D))
-    Ty = VD->getType();
-  else
-    Ty = Context.getTagDeclType(cast<TagDecl>(D));
-  if (Ty->isDependentType() || Ty->isIncompleteType())
+  QualType UnderlyingTy, DiagTy;
+  if (ValueDecl *VD = dyn_cast<ValueDecl>(D)) {
+    UnderlyingTy = DiagTy = VD->getType();
+  } else {
+    UnderlyingTy = DiagTy = Context.getTagDeclType(cast<TagDecl>(D));
+    if (EnumDecl *ED = dyn_cast<EnumDecl>(D))
+      UnderlyingTy = ED->getIntegerType();
+  }
+  if (DiagTy->isDependentType() || DiagTy->isIncompleteType())
     return;
 
   // C++11 [dcl.align]p5, C11 6.7.5/4:
@@ -2977,10 +2980,10 @@ void Sema::CheckAlignasUnderalignment(De
 
   if (AlignasAttr && Align) {
     CharUnits RequestedAlign = Context.toCharUnitsFromBits(Align);
-    CharUnits NaturalAlign = Context.getTypeAlignInChars(Ty);
+    CharUnits NaturalAlign = Context.getTypeAlignInChars(UnderlyingTy);
     if (NaturalAlign > RequestedAlign)
       Diag(AlignasAttr->getLocation(), diag::err_alignas_underaligned)
-        << Ty << (unsigned)NaturalAlign.getQuantity();
+        << DiagTy << (unsigned)NaturalAlign.getQuantity();
   }
 }
 

Modified: cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp?rev=226653&r1=226652&r2=226653&view=diff
==============================================================================
--- cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp (original)
+++ cfe/trunk/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp Wed Jan 21 04:54:38 2015
@@ -15,6 +15,12 @@ enum alignas(1) E1 {}; // expected-error
 enum alignas(1) E2 : char {}; // ok
 enum alignas(4) E3 { e3 = 0 }; // ok
 enum alignas(4) E4 { e4 = 1ull << 33 }; // expected-error {{requested alignment is less than minimum alignment of 8 for type 'E4'}}
+enum alignas(8) E5 {};
+static_assert(alignof(E5) == 8, "");
+
+typedef __attribute__((aligned(16))) int IntAlign16;
+enum E6 : IntAlign16 {};
+static_assert(alignof(E6) == 4, "");
 
 struct S1 {
   alignas(8) int n;

Modified: cfe/trunk/test/Sema/align-x86.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/align-x86.c?rev=226653&r1=226652&r2=226653&view=diff
==============================================================================
--- cfe/trunk/test/Sema/align-x86.c (original)
+++ cfe/trunk/test/Sema/align-x86.c Wed Jan 21 04:54:38 2015
@@ -27,6 +27,8 @@ double g6[3];
 short chk1[__alignof__(g6) == 8 ? 1 : -1];
 short chk2[__alignof__(double[3]) == 8 ? 1 : -1];
 
+enum { x = 18446744073709551615ULL } g7;
+short chk1[__alignof__(g7) == 8 ? 1 : -1];
 
 // PR5637