add a new "getPreferredTypeAlign" method to return the preferred alignment
of a type. The implementation is currently something of a hack, but is
sufficient for now and allows clients to be built on it.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63108 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/ASTContext.h b/include/clang/AST/ASTContext.h
index 684feb2..a01199d 100644
--- a/include/clang/AST/ASTContext.h
+++ b/include/clang/AST/ASTContext.h
@@ -394,8 +394,8 @@
return getTypeInfo(T).first;
}
- /// getTypeAlign - Return the alignment of the specified type, in bits. This
- /// method does not work on incomplete types.
+ /// getTypeAlign - Return the ABI-specified alignment of a type, in bits.
+ /// This method does not work on incomplete types.
unsigned getTypeAlign(QualType T) {
return getTypeInfo(T).second;
}
@@ -403,6 +403,12 @@
return getTypeInfo(T).second;
}
+ /// getPreferredTypeAlign - Return the "preferred" alignment of the specified
+ /// type for the current target in bits. This can be different than the ABI
+ /// alignment in cases where it is beneficial for performance to overalign
+ /// a data type.
+ unsigned getPreferredTypeAlign(const Type *T);
+
/// getDeclAlign - Return the alignment of the specified decl that should be
/// returned by __alignof(). Note that bitfields do not have a valid
/// alignment, so this method will assert on them.
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 2662860..e7c08e2 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -453,6 +453,22 @@
return std::make_pair(Width, Align);
}
+/// getPreferredTypeAlign - Return the "preferred" alignment of the specified
+/// type for the current target in bits. This can be different than the ABI
+/// alignment in cases where it is beneficial for performance to overalign
+/// a data type.
+unsigned ASTContext::getPreferredTypeAlign(const Type *T) {
+ unsigned ABIAlign = getTypeAlign(T);
+
+ // Doubles should be naturally aligned if possible.
+ if (const BuiltinType *BT = dyn_cast<BuiltinType>(getCanonicalType(T)))
+ if (BT->getKind() == BuiltinType::Double)
+ return std::max(ABIAlign, 8U);
+
+ return ABIAlign;
+}
+
+
/// LayoutField - Field layout.
void ASTRecordLayout::LayoutField(const FieldDecl *FD, unsigned FieldNo,
bool IsUnion, unsigned StructPacking,