================
Comment at: lib/Sema/SemaInit.cpp:3245-3246
@@ +3244,4 @@
+ return;
+ if (SemaRef.Diags.isIgnored(diag::warn_pessimizing_move_on_initialization,
+ InitExpr->getLocStart()))
+ return;
----------------
This check is not especially cheap, and the code below will be cheap in most
cases; it's probably better to omit this.
================
Comment at: lib/Sema/SemaInit.cpp:3249
@@ +3248,3 @@
+
+ const CallExpr *CE = dyn_cast<CallExpr>(InitExpr);
+ if (!CE || CE->getNumArgs() != 1)
----------------
Maybe `IgnoreParens` before the cast?
================
Comment at: lib/Sema/SemaInit.cpp:3259
@@ +3258,3 @@
+
+ const Expr *Arg = CE->getArg(0)->IgnoreImplicit();
+ if (!Arg->isRValue() || !Arg->getType()->isRecordType())
----------------
Maybe `IgnoreParens` here too.
================
Comment at: lib/Sema/SemaInit.cpp:3392-3393
@@ -3361,1 +3391,4 @@
+
+ if (Args.size() == 1)
+ CheckMoveOnConstruction(S, Args[0]);
}
----------------
You should defer the diagnostic until we perform the `InitializationSequence`.
We might select a different initialization sequence or overload candidate and
not actually call this constructor.
================
Comment at: lib/Sema/SemaStmt.cpp:3049
@@ -3048,1 +3048,3 @@
+static void CheckMoveOnReturn(Sema &SemaRef, const Expr *ReturnExpr,
+ const FunctionDecl *FD) {
----------------
This looks familiar. Can some commonality be factored out here?
Or, better, can you implement both checks in a single place? When performing
the initialization sequence, you can ask the initialized entity whether it's
the returned object in a return statement.
================
Comment at: lib/Sema/SemaStmt.cpp:3080-3081
@@ +3079,4 @@
+
+ if (!SemaRef.Context.hasSameUnqualifiedType(ReturnType, VD->getType()))
+ return;
+
----------------
If the types don't match, you aren't likely to have a pessimizing move (elision
would only occur if your return type's constructor took its argument by value),
but perhaps we should still produce some kind of "redundant move" warning. (Per
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1579, you get an
implicit move no matter what the types are.)
http://reviews.llvm.org/D7633
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