Fix for issue ldc-developers#624

Author: redstar

gen/functions.cpp

@@ -138,8 +138,17 @@ llvm::FunctionType* DtoFunctionType(Type* type, IrFuncTy &irFty, Type* thistype,
     {
 #if LDC_LLVM_VER >= 303
         llvm::AttrBuilder attrBuilder;
-        if (isCtor)
-            attrBuilder.addAttribute(llvm::Attribute::Returned);
+// Issue 624: In case of a ctor 'this' is passed to the function and is also
+// the return value. This could be a perfect case for the 'Returned' attribute.
+// However the 'this' type and the return type are transformed in different
+// ways, making them bitcast incompatible.
+// Example: extern(C): struct Value { this(string) {} string s; }
+// return type: { i64, i64 }
+// this type:   %ldc_github_624.Value*
+// FIXME: (1) Investigate why the types are handled in different ways
+//        (2) The attributes are cleared by some abi implementations
+//        if (isCtor)
+//            attrBuilder.addAttribute(llvm::Attribute::Returned);
 #endif
         newIrFty.arg_this = new IrFuncTyArg(thistype, thistype->toBasetype()->ty == Tstruct
 #if LDC_LLVM_VER >= 303