rsmith added a comment.
Thank you for working on this! Please also add a test to
test/CXX/drs/dr15xx.cpp with a "// dr1579: 3.9" comment (we have a script that
turns those comments into www/cxx_dr_status.html).
================
Comment at: include/clang/Sema/Sema.h:3473
@@ -3472,3 +3472,3 @@
VarDecl *getCopyElisionCandidate(QualType ReturnType, Expr *E,
- bool AllowFunctionParameters);
+ bool AllowParamOrMoveConstructable);
bool isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
----------------
Constructable -> Constructible.
================
Comment at: lib/Sema/SemaStmt.cpp:2756-2759
@@ -2755,4 +2755,6 @@
// ... the same cv-unqualified type as the function return type ...
if (!VDType->isDependentType() &&
- !Context.hasSameUnqualifiedType(ReturnType, VDType))
- return false;
+ !Context.hasSameUnqualifiedType(ReturnType, VDType)) {
+ // When considering moving this expression out, allow dissimilar types.
+ if (!AllowParamOrMoveConstructable)
+ return false;
----------------
Combine these conditions into a single `if`, and put the (cheapest) `bool`
check first.
================
Comment at: lib/Sema/SemaStmt.cpp:2773-2783
@@ -2769,13 +2772,13 @@
// ...non-volatile...
if (VD->getType().isVolatileQualified()) return false;
// __block variables can't be allocated in a way that permits NRVO.
if (VD->hasAttr<BlocksAttr>()) return false;
// Variables with higher required alignment than their type's ABI
// alignment cannot use NRVO.
if (!VD->getType()->isDependentType() && VD->hasAttr<AlignedAttr>() &&
Context.getDeclAlign(VD) > Context.getTypeAlignInChars(VD->getType()))
return false;
----------------
None of this should be checked for the `AllowParamOrMoveConstructible` case.
================
Comment at: lib/Sema/SemaStmt.cpp:2820
@@ -2814,5 +2819,3 @@
- // [...] If overload resolution fails, or if the type of the first
- // parameter of the selected constructor is not an rvalue reference
- // to the object's type (possibly cv-qualified), overload resolution
- // is performed again, considering the object as an lvalue.
+ InitializationKind Kind = InitializationKind::CreateDirect(
+ Value->getLocStart(), Value->getLocStart(), Value->getLocEnd());
----------------
Why are you using direct-initialization here? The return value should always be
copy-initialized.
http://reviews.llvm.org/D21619
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