Verification of Parameterised FPGA Circuit Descriptions with Layout ...

CHAPTER 7. CONCLUSION AND FUTURE WORK 168
7.3 Comparison with Related Work
To our knowledge, ours is the only work which addresses the issue of generating and verifying
parameterised hardware libraries with explicit placement information and support for recur-
sively and iterative described structures. However, other work has taken different approaches
to the problem.
7.3.1 VHDL with Explicit Co-ordinates
VHDL and Verilog can be used with absolute placement co-ordinates specified using “RLOC”
constraints for Xilinx architectures. VHDL does not provide any particular support for place-
ment in particular, however it can be extended with user-defined functions to implement the
equivalent of our maxf and sum operations. VHDL does not support higher-order functions,
however, so these would need to be coded explicitly for each hardware arrangement.
Nevertheless, our theorem proving verification framework could be applied to VHDL designs.
The potential for the use of a few dozen key theorems to automate proofs is severely reduced
by the lack of higher-order functions however theorem proving can still be used to verify
first-order placement co-ordinates. Size functions for each VHDL entity would probably
need to be entered manually, although they could possibly be inferred in a similar way to
Quartz providing a suitable subset of the language is used. VHDL allows the combination
of behavioural and structural design styles within a single description and if this was done
then verification of the correctness of entity size functions would probably be impossible
without incorporating a theoretical model of how behavioural descriptions are elaborated
into structural hardware.
7.3.2 Relative Placement in Pebble
Pebble has been extended with support for relative placement [49]. The Pebble system uses
new language constructs to provide below, beside, below for and beside for capabilities and
a functional specification has been given for a procedure which compiles relative positions
into absolute co-ordinates. The Pebble system is clean and effective at describing many