Also known as communication semantics, I think. The pass adds an extra channel parameter per mobile (perhaps in future this could be a single extra channel?) that is used to send back the mobile value, and hacked the backend so that the communications to receive these mobiles are done in the right place (after the processes have been run, but before waiting on the barrier for them to complete).
cgtest83 now compiles, runs and passes without a segfault.
Surprisingly, the generated code seems to be compiled by GCC without warnings. Array subscripts are currently unimplemented (a star, i.e. equivalent of subscript 0) is used wherever there should be a subscript.
The new mechanism is based on working out the C type of the original variable/abbrev-mode, the C type of the desired variable/abbrev-mode, and works out how many *s or &s to insert to coerce it to the right type.
Previously, such a function was an IntrinsicFunctionCall inside one expression of an ExpressionList, which the type-checker rejected. I've had to add a new constructor to ExpressionList, and I've quickly hacked together the line in the C backend to make it work -- but it does seem to work.
Fixes#37. The change itself was very easy, but the main problem was to then go and change everything in GenerateCTest that had been written using A.Int as a test type.
This is mostly straightforward: modify the parser to allow direction
decorators in the right places, and extend the type checker to match.
There's some slight awkwardness in that some of the Types functions
have to perform the same checks as the type checker (e.g. directing a
non-channel), so I've tidied up their error messages a bit.
At the backend, I've just added a little pass to strip out all the
DirectedVariables, since the other backend passes don't handle them
gracefully. From the occam/C point of view this is fine, but I'm not
sure if it's going to cause problems for C++.
I'm pretty sure this test used to fail and got fixed, but I think the
test was fixed to match the incorrect code rather than the other way
around. What it's testing is the abbreviation of a channel end as an
identically-typed channel end, which (since they're both pointers)
should look something like:
Channel *c;
Channel *d = c;
Instead it was generating "d = &c", which broke cgtest87.
The change made to GenerateC to fix this feels a bit awkward to me --
it's very simple, but it's yet another special case in genVariableAM.
All of the genVariable code could really use reworking (again),
perhaps to use some internal representation of the C expression...
