You may remember that i was asking about customising a compiler so it did not use certain instructions so it could be used with an asic core which supports a subset of 8052 instructions.
The solution i finally came up with is to use a normal C compiler but write the VHDL so that only the hardware needed to support the instructions in the compiled code is actually generated,which means that you get a custom processor for each program,with only the hardware needed to support the instructions in the code.Which works because as the asic is meant for use in smart cards nobody is going to change the code once it is written.It does mean that the HDL is slightly complicated(erk) but the customer is happy which is all that matters.
Its alot easier than trying to write a c compiler which does not use rotates,shifts or decimal adjusts for example.