HLSL: Intercept flatten aggregates passed to a function input, and copy member-by-member.

Test/hlsl.entry-in.frag

@@ -4,10 +4,17 @@ struct InParam {
     int2 i2;
 };
 
+float fun(InParam p)
+{
+    return p.v.y + p.fragCoord.x;
+}
+
 float4 PixelShaderFunction(InParam i) : COLOR0
 {
     InParam local;
     local = i;
+    float ret1 = fun(local);
+    float ret2 = fun(i);
 
-    return local.fragCoord;
+    return local.fragCoord * ret1 * ret2;
 }