Function calls in general can still be used to hide escaping
allocations from the compiler (issue #1497), but these calls in
particular always allocate, so we can easily and accurately handle
them.
This reverts commits f8d1506922
and cf19c9512d.
While the commit just fixes a clear typo in the implementation,
it turns out the original algorithm isn't flexible enough to
capture functions that transitively return references to
long-lived data. For instance, while cache_get() is special-cased
in the compiler to be recognised as returning a value of Global()
lifetime, a function just forwarding to it (as seen in the
embedding tests) isn't anymore.
A separate issue is also that this makes implementing functions
that take lists and return references to global data in user code
impossible, which central parts of the Oxford codebase rely on.
Just reverting for now to unblock master; a fix is easily designed,
but needs testing.
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.
Internal variables are assumed to be scoped correctly
(including not being accessed uninitialized).
This was changed from "." because artiq.compiler.embedding uses
"." in module prefix of function names.
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.
David Nadlinger
whitequark