A recent GC change (included with the set-of-scopes expander)
allows the GCs marking procedure to recur directly to a limited
depth, instead of always pushing pointers onto a stack. Direct
recursion is not cmopatible with ephemeron-resolution process,
so switch to no-recur mode.
This problem was uncovered by an existing test.
The combination of splitting a `letrec` and optimizing
the resulting `(let ([x <proc>]) x)` to just `<proc>`
used a bad coordinate shift, which made property testing
incorrect, etc.
For reasons that are not clear, the new expander triggered
the problem through an existing test.
The `eval-syntax` function (which is used by other functions, such as
loading a module) should not install fallback-binding scopes from
the current namespace.
When `(let ([x ...]) (let ([y x]) ... y ... y ...))` turns into
`(let ([x ...]) ... x ... x ...)`, make sure that `x` is not
still marked as single-use. Incorrect marking as single-use could
cause the optimizer to inline too much, for example.
Thanks to Gustavo for tracking down the problem.
Previously all the predicates recognized only non-#f things, so ´not´ can be
added to the list of disjoint predicates. But many of the parts of the code
relied on the non-#f property and had to be modified.
In (if (eq? x <pred?-expr>) <tbranch> <fbranch>) infer that the type of
x is pred? in the tbranch.
Also, reduce (eq? x y) => #f when the types are different.
The optimizer reduces the variables with a known type to #t in a Boolean context.
But some predicates imply that the variable has a definite values, so they can be
reduced in a non-Boolean context too.
For example, in (lambda (x) (if (null? x) x 0))) reduce the last x ==> null.
This fixes the bug twice:
* Don't reduce mutable variables with a type to #t in a Boolean context.
* Don't record the type of mutable variables when a predicate is
checked in a test condition.
While reducing some ignored constructors, the optimizer may wrap the arguments
<expr> in (values <expr>) to ensure that it's a single value non-cm expression.
This avoids the unnecessary nesting of (values (values <expr>)).
Similarly, add the cases for begin and begin0 to single_valued_noncm_expression
When a package "p" is clone-linked and the repo for "p" changes to be
a multi-package repository (e.g., with "p-lib", "p-doc", and "p"), a
`raco update` would get confused. Unofrtunately, a plain `raco pkg
update p` can't work in that case, because the clone link would still
be a pathless repo URL; the repairs make `raco pkg update --lookup
--clone ..../p` work as is should.
Related: fix inference of package names in the early check for whether
a package is installed.
While `#:in-original-place? #t` provides one way to serialize
foreign calls, it acts as a single lock and requires expensive
context switches. Using an explicit lock can be more efficient
for serializing calls across different places.
For example, running "plot.scrbl" takes 70 seconds on my machine
in the original place and using `#:lock-name` in any place,
while it took 162 seconds in a non-main place with Cairo+Pango
serialization via `#:in-original-place? #t`.
Internally, the named lock combines compare-and-swap with a
place channel. That strategy gives good performance in the case
of no contention, and it cooperates properly with the Racket
scheduler where there is contention.
The optimizer was able to use the type information gained outside
the let's to reduce expressions inside the lets. For example, in
(lambda (z) (car z) (let ([o (random)]) (pair? z)))
it reduces (pair? z) ==> #t.
This enable the propagation in the other direction so in
(lambda (z) (let ([o (random)]) (car z)) (pair? z))
it reduces (pair? z) ==> #t too.
Using `(thread-resume t1 t2)` would not prevent a GC of t1, but it
would create an intermediate record to make the link from t1 to t2,
and that intermediate record would leak due to a missing level of
indirection in a table-cleanup traveral. The leak not only accumulated
memory, it also caused ever slower traversals of the table in an
attempt to clean up.
(Since the leak is small and the leaking object is not directly
accessible, I don't have a good idea on how to test this repair
automatically, but see the program in the PR.)
Closes PR 15099.
Modern OS configurations likely use an even larger buffer size, and
making it small can have substantial negative performance effects
(e.g., with PostgreSQL over TCP).
