Note that because we changed exception representation from using string
names as exception identifier into using integer IDs, we need to
initialize the embedding map in order to allocate the integer IDs. Also,
we can no longer print the exception names and messages from the kernel,
we will need the host to map exception IDs to names, and may need the
host to map string IDs to actual strings (messages can be static strings
in the firmware, or strings stored in the host only).
We now check for exception IDs for lit tests, which are fixed because we
preallocated all builtin exceptions.
Exception name is replaced by exception ID, which requires no
allocation. Other strings in the exception can now be 'host-only'
strings, which is represented by a CSlice with len = usize::MAX and
ptr = key, to avoid the need for allocation when raising exceptions
through RPC.
This allows assert() to be used on Zynq, where abort() is not
currently implemented for kernels. Furthermore, this is arguably
the more natural implementation of assertions on all kernel targets
(i.e. where embedding into host Python is used), as it matches host
Python behavior, and the exception information actually makes it to
the user rather than leading to a ConnectionClosed error.
Since this does not implement printing of the subexpressions, I
left the old print+abort implementation as default for the time
being.
The lit/integration/instance.py diff isn't just a spurious change;
the exception-based assert implementation exposes a limitation in
the existing closure lifetime tracking algorithm (which is not
supposed to be what is tested there).
GitHub: Fixes#1539.
Specifically, the following idiom broke our CFGSimplifier:
b1:
branch_if %cond, %b2, %b3
b2:
branch %b3
b3:
%v = phi [ %b2 => 0, %b3 => 1 ]
This is very annoying to properly handle in general case, and also
this (specifically %b2) is exactly what broke LocalAccessValidator
in the first place. So, remove CFGSimplifier altogether.
Instead, teach LocalAccessValidator how to look through predecessors
in order to get a location.
As a result, the dominator tree can now process arbitrary (reducible)
CFGs and we do not run DCE before analyses, risking loss of
correspondence to the AST, which would arbitrarily silence analyses.
Unification-based inference for regions is useful with a language
that has let bindings (which would propagate the regions) and
functions polymorphic over regions. For reasons of simplicity,
ARTIQ has neither, and making unification-based inference work would
essentially mean adding region coercions between most AST nodes,
and having every source subexpression have its own region variable,
with the appropriate subtyping relationship.
It's simpler to just keep that state outside of typedtree.