Espruino speed improvements - compiled JavaScript?

I get the same thing here - I'm afraid there's some kind of problem with the compiled code's handling of function parameters. I haven't been able to figure it out yet I'm afraid.

For instance:

function t(a,b,c) { 
  "compiled";
  return a+","+b+","+c;
}

>t(1,2,3)
="1,1,3"
>t("a","b","c")
="a,a,c"

However the C++ function that's being created from it appears to be fine:

extern "C" {
 JsVar *myFunction(JsVar *a, JsVar *b, JsVar *c) {
  return SV(jsvMathsOp(SV(jsvMathsOp(SV(jsvMathsOp(SV(jsvMathsOp(SV::notOwned(a), SV(jsvNewFromString(",")), '+')), SV::notOwned(b), '+')), SV(jsvNewFromString(",")), '+')), SV::notOwned(c), '+')).give();
  return 0; // just in case
 }
}

(SV is a 'smart pointer' class). I can only assume it's something to do with the way GCC is actually compiling the code :(