December 31st, 2013
I’ve been dogfooding my VHDL compiler for a project at work and now that it’s gotten to the point where it can simulate non-trivial designs, compile times are becoming significant. Especially when files use Xilinx primitives as the
vcomponents library takes a while to load.
At the moment I’m re-analysing every source file for each change I make, so obviously an improvement would be to write a makefile and only re-analyse the files that have changed and those that depend on them (e.g. an architecture must be re-analysed if the corresponding entity changed). But figuring out and maintaining the dependencies by hand is tedious and error prone so I’ve written a makefile generator that recursively finds the dependencies for previously analysed or elaborated units in a library. Invoke it like this:
nvc --make my_top_level >Makefile
make will do the minimum amount of work to rebuild all the out of date files. If the argument to
--make is an elaborated design then two convenience targets
wave will be added to run the simulation and run with waveform output respectively.
The code is fairly compact: only 400 or so lines of C.
This also turned out to be handy for solving a long-standing problem of not being able to bootstrap the standard and IEEE libraries with parallel make (
make -j). Previously the dependencies in the automake input file were incomplete, but now these are generated automatically by a
gen-deps target. The output (e.g. here) is then mangled with sed and committed into the git repository (this solves a chicken-and-egg problem where the
gen-deps target can only be run in an already built tree).
December 31st, 2013
After a hiatus of over 20 years I got another Pirate Lego set for Christmas! My parents tracked down from eBay the one set I was missing from the 1989/90 Pirate range, 6270 “Forbidden Island”. Got all the bits and the original instructions! Flag was a bit borked by I replaced it with a spare on I had.
Here it is with the big pirate ship and raft. Probably acquired those on some previous Christmas. Apparently there’s some newfangled “Pirates of the Caribbean” themed pirate Lego: kids these days…
December 22nd, 2013
I went for another adventure today from Farnham Common near Slough to West Drayton just inside the M25. You might recall I’ve been roughly this way on several previous adventures. A really nice sunny day despite the pessimistic weather forecast.
A lot of the photos below are from Stoke Common a really lovely area of boggy grassland north east of Slough. I’ve been here several times and always enjoyed walking through it. Definitely worth visiting if you live in the area.
Near the end of the trip, just inside the M25, I had to take a less pleasant detour around a sewage works as a vital foot bridge over the canal had been inconsiderately demolished.
December 16th, 2013
This evening I went running for exactly 41 minutes 41 seconds and 41 hundredths of a second.
December 16th, 2013
Ah, the humble can of compressed air: is there any problem it can’t solve? Just now with his sidekick Henry he managed to repair my dead CPU fan!
December 15th, 2013
Almost a year since I released the last one, there’s a new lander-0.6.5.tar.gz package available. Nothing exciting: just fixing bit rot and some FreeBSD build fixes Dmitry Marakasov. Glad someone’s using it!
December 14th, 2013
I saw some pretty red berries when I was out adventuring near Marlow today. Probably highly toxic.
Really lovely winter morning today: cold and a sunny and muddy. I saw a robin which must mean it’s nearly Christmas!
November 30th, 2013
I Went exploring in Wantage, Oxfordshire today. It’s a nice little market town that’s apparently the birth place of Alfred the Great.
The local museum was unexpectedly brilliant. My favourite bit was this replica of a Wantage tram carriage complete with dead mice:
Predictably everything hereabouts is named after Alfred. Here’s King Alfred’s school which is a rather attractive building:
Afterwards I went for a semi-circular walk back to Didcot through the Lambourn Downs and Ridgeway that I’ve visited before. I stopped for lunch here by this huge hill.
November 24th, 2013
I recently added a code coverage option to the VHDL compiler, nvc, I’m working on. I tend to find code coverage a really useful tool when I’m writing RTL, especially the sort of control-dominated designs I do in my day job. I find Modelsim’s HTML coverage reports a bit frustrating so I’m trying to do something more user-friendly in my simulator.
If you elaborate your design with the
--cover option the generated code will be annotated to gather the following kinds of coverage:
- Statement – A counter is added for each executable statement in the design. A statement must be executed at least once to be “covered”.
- Branch – A branch is covered if it is both taken and not-taken at least once during execution
- Condition – A condition here is a Boolean sub-expression of branch test and it is covered by evaluating to both TRUE and FALSE at least once. For example
if A and B then contains one branch but two sub-conditions.
After a run with coverage enabled the statistics are automatically reported:
** Note: coverage report generated in /tmp/work/WORK.TEST.cover/
282/289 statements covered
71/94 branches covered
85/108 conditions covered
A HTML report is then generated which contains a top-level summary and a detailed report for each source file:
You can mouse over a non-covered branch or condition to get a hint as to why it was not covered.
The implementation is currently a work-in-progress but functions well enough for light usage. The biggest limitation at the moment is that the report only contains aggregated statistics per-file rather than per-instance statistics.
October 30th, 2013
Walking from Henley to Oxford has been something I wanted to try for ages, so having a day off this Tuesday I thought I’d give it a go. It’s about 25 or so miles if you take the scenic route. Unfortunately I think this should have been a summer project as despite setting off at 8am I ran out of day light around 5:30 a few miles short in a village called Marsh Baldon and had to escape via a well-timed bus. I’ll blame the amount of debris from Monday’s storm for slowing me down.
Some photos from epic adventure below: