Convert struct arg to integer when passing inreg to make sure LLVM doesn't

ignore the attribute!

dmd/mtype.h

@@ -23,6 +23,7 @@
 
 // llvm
 #include "../ir/irtype.h"
+namespace llvm { class Type; }
 
 struct Scope;
 struct Identifier;
@@ -438,7 +439,8 @@ struct TypeFunction : Type
     bool retInPtr;
     bool usesThis;
     bool usesNest;
-    bool structInregArg;
+    // when the last arg is a struct and passed in EAX, this holds its real type
+    const llvm::Type* structInregArg;
     unsigned retAttrs;
     unsigned thisAttrs; // also used for nest
     // parameter index in the llvm function that contains the first not-implicit arg