The idea is to start splitting the
HLSL IR -> d3dbc
translation into
HLSL IR -> vsir -> d3dbc
So hlsl_sm1_write is split into two functions, sm1_generate_vsir()
which should handle the first part and d3dbc_compile() which should
handle the second part.
This translation should be completed once the hlsl_ctx and entry_func
are no longer used in d3dbc_compile().