When performing a trivial copy of a C++ type, we must be careful not
to overwrite objects that might have been allocated into the type's
tail padding. This patch is missing some potential optimizations where
the destination is provably a complete object, but it's necessary for
correctness.
Patch by Jonathan Sauer.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@162254 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 0452730..7c685cf 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -1080,6 +1080,27 @@
return toCharUnitsFromBits(Align);
}
+// getTypeInfoDataSizeInChars - Return the size of a type, in
+// chars. If the type is a record, its data size is returned. This is
+// the size of the memcpy that's performed when assigning this type
+// using a trivial copy/move assignment operator.
+std::pair<CharUnits, CharUnits>
+ASTContext::getTypeInfoDataSizeInChars(QualType T) const {
+ std::pair<CharUnits, CharUnits> sizeAndAlign = getTypeInfoInChars(T);
+
+ // In C++, objects can sometimes be allocated into the tail padding
+ // of a base-class subobject. We decide whether that's possible
+ // during class layout, so here we can just trust the layout results.
+ if (getLangOpts().CPlusPlus) {
+ if (const RecordType *RT = T->getAs<RecordType>()) {
+ const ASTRecordLayout &layout = getASTRecordLayout(RT->getDecl());
+ sizeAndAlign.first = layout.getDataSize();
+ }
+ }
+
+ return sizeAndAlign;
+}
+
std::pair<CharUnits, CharUnits>
ASTContext::getTypeInfoInChars(const Type *T) const {
std::pair<uint64_t, unsigned> Info = getTypeInfo(T);