When using "--variable" as an argument to an inout function, 2 is subtracted not one

https://godbolt.org/z/73so7qzzW

`void Func(inout uint byteOffset)
{
}`

`uint PSMain(uint i : I) : SV_TARGET
{
    Func(--i);  // Subtracts 2...
    return i;   
}`

The resulting DXIL has an "Add minus two" operation, not "add minus one".

`%2 = add i32 %1, -2, !dbg !37 `