Set up bindings and shift phases as needed to make
`variable-reference->namespace` work in a run-time position when the
enclosing module is instantiated at a phase other than 0.
Thanks to Rohin Shah for the bug report.
Support an external implementation of `read-syntax` by exposing
functionality that is currently internal to `read-syntax`: a srcloc
argument to a "special"-producing port function and wrapping special
results to reliably distinguish them from characters.
When multiple-binding `let-values` form is split into a single-binding
form on the grounds that the right-hand side will definitely error,
the optimizer's effect clocks were advance incorrectly.
Closes#1552
For example, an `unsafe-unbox` call should not be moved past the
call to an unknown function that might change a box's content.
Thanks to Sergey Pinaev for the report.
The objective of lookup_constant_proc and the first part of
optimize_for_inline was to find out if the value of an expression was a
procedure and get it to analyze its properties or try to inline it. Both
were called together in a few places, because each one had some special
cases that were missing in the other.
So, move the lookup and special cases from optimize_for_inline to
lookup_constant_proc, and keep only the code relevant to inlinig in
optimize_for_inline.
Both function have a similar purpose and implementation, so merge them to consider
all the special cases for both uses.
In particular, detect that:
(if x (error 'e) (void)) is single-valued
(with-continuation-mark <chaperone-key> <val> <omittable>) is not tail sensitive.
Also, as ensure_single_value was checking also that the expression was has not a
continuation mark in tail position, it added in some cases an unnecessary
wrapper. Now ensure_single_value checks only that the expression produces
a single vale and a new function ensure_single_value_noncm checks both
properties like the old function.
Adjust list and stream handling as sequences so that during the body
(for ([i (in-list l)])
....)
then `i` and its cons cell in `l` are not implicitly retained while
the body is evaluated. A `for .... in-stream` similarly avoids
retaining the stream whose head is being used in the loop body.
The `map`, `for-each`, `andmap`, and `ormap` functions are similarly
updated.
The `make-do-sequence` protocol allows an optional extra result so
that new sequence types could have the same properties. It's not clear
that using `make-do-sequence` is any more useful than creating the new
sequence as a stream, but it was easier to expose the new
functionality than to hide it.
Making this work required a repair to the optimizer, which would
incorrectly move an `if` expression in a way that could affect
space complexity, as well as a few repairs to the run-time system
(especially in the vicinity of the built-in `map`, which we should
just get rid of eventually, anyway).
Compile a `for[*]/list` form to behave more like `map` by `cons`ing
onto a recursive call, instead of accumulating a list to reverse.
This style of compilation requires a different strategy than before.
A form like
(for*/fold ([v 0]) ([i (in-range M)]
[j (in-range N)])
j)
compiles as nested loops, like
(let i-loop ([v 0] [i 0])
(if (unsafe-fx< i M)
(i-loop (let j-loop ([v v] [j 0])
(if (unsafe-fx< j N)
(j-loop (SEL v j) (unsafe-fx+ j 1))
v))
(unsafe-fx+ i 1))
v))
instead of mutually recursive loops, like
(let i-loop ([v 0] [i 0])
(if (unsafe-fx< i M)
(let j-loop ([v v] [j 0])
(if (unsafe-fx< j N)
(j-loop (SEL v j) (unsafe-fx+ j 1))
(i-loop v (unsafe-fx+ i 1))))
v))
The former runs slightly faster. It's difficult to say why, for
certain, but the reason may be that the JIT can generate more direct
jumps for self-recursion than mutual recursion. (In the case of mutual
recursion, the JIT has to generate one function or the other to get a
known address to jump to.)
Nested loops con't work for `for/list`, though, since each `cons`
needs to be wrapped around the whole continuation of the computation.
So, the `for` compiler adapts, depending on the initial form. (With a
base, CPS-like approach to support `for/list`, it's easy to use the
nested mode when it works by just not fully CPSing.)
Forms that use `#:break` or `#:final` use the mutual-recursion
approach, because `#:break` and #:final` are easier and faster that
way. Internallt, that simplies the imoplementation. Externally, a
`for` loop with `#:break` or `#:final` can be slightly faster than
before.
The optimizer can detect that some expressions will escape through
an error, and it can discard surrounding code in that case. It should
not change the tailness of a `with-continuation-mark` form by
liftng it out of a nested position, however. Doing so can eliminate
stack frames that should be visible via errotrace, for example.
This change fixes the optimizer to wrap an extra `(begin ... (void))`
around an expression if it's lifted out of a nested context and
might have a `with-continuation-mark` form in tail position.
In
(with-syntax ([x ....])
#'(x y))
and property on the source syntax object `(x y)` was lost in
constructing a new syntax object to substitute for `x`, while
properties on preserved literal syntax objects, such as `y`
were intact. Change `syntax` to preserve properties for
reconstructed parts of the template.
This change exposes a problem with 'transparent taint modes,
where the internal "is original?" property was preserved while
losing scopes that wuld cancel originalness. So, that's fixed
here, too.
extend optimize_ignore to go inside expressions with
begin, begin0 and let.
Also, try to reuse begin's in the first argument of
make_discarding_sequence.
If a mutable hash table changes while it's being printed,
various parts of the printing function could see a mismatch
between the current size and an old array size. To avoid this
problem, extract the size whenever extracting the array.
An identifier that gets a module context via `module->namespace` plus
`namespace-syntax-introduce` should not count as having the module as
its source as reported by `syntax-source-module`.
The correct behavior happened for the wrong reason prior to commit
cb6af9664c.
Closes#1515
For a template expression that involevs ellipses, a wrapper is added
to catch failures an report as an "incompatible ellipsis match count"
error. The wrapper was only added when there are multiple pattern
variables with ellipses, but it turns out that it's possible to fail
with incompatible counts using a single pattern variable.
Besides handlign that case, the revised check avoids an unnecessary
wrapper in cases where multiple pattern variables have ellipses but
they are used independently in a template.
Closes#1511
Without this repair,
#lang racket/base
(require 2htdp/abstraction)
(for/list ((dropping-which-one (in-naturals)))
1)
fails to compile with a "optimizer clock tracking has gone wrong"
error. A variant of this test (that doesn't depend on `2htdp`)
is now in the "optimize.rktl"; a simpler and more direct test
should be possible, but I wasn't able to construct one.
When a thread that is blocked on a set of semaphores and channels
is suspended and resumed after one of the events becomes ready,
and if the event has a wrapper function, then the wrapper was
not applied and the event selection was not reported correctly.
Thanks to Philip McGrath for reporting the problem.
This kind of reductions were applied only when x or y was a constant.
Classify the relevant predicates in 4 categories. In particular,
if <expr> satisfy pred? we can use this classification to apply
the correct reduction:
(equal? <expr> y) ==> [no reduction, unless y has a different type]
(equal? <expr> y) ==> (eqv? <expr> y)
(equal? <expr> y) ==> (eq? <expr> y)
(equal? <expr> y) ==> (begin <expr> (pred? y))
Also, add a new primitive interned-char? that is hidden, but it's
useful to track in the optimizer the the chars? with a value < 256
that are interned because they are treated specially, and if they
are equal? then they are eq?.
... + prefix-in + relative-path module. All of those ingredients
(or some similar alternatives) are necessary to trigger a slow
way of saving module context for interaction evaluation where
a module-path index shift was getting lost.
Previously the relevant predicates where disjoint, and until this commit
the only predicate that recognizes #f was `not`. So it's necessary to fix
two reductions to allow other predicates that recognize #f, like `boolean?`.
Add a hidden `true-object?` primitive that recognizes only #t, that is also
useful to calculate unions and complements with `boolean?` and `not`.
Also, extend a special case for expressions like
(or (symbol? x) (something))
where the optimizer is confused by the temporal variable that saves the
result of `(symbol? x)`, and the final expression is equivalent to
(let ([temp (symbol? x)])
(if temp #t (something)))
This extension detects that the temporal variable is a `boolean?` and
reduces the expression to
(if (symbol? x) #t (something))
* Wrong contract for syntax-local-value in the documentation.
* Clarified signature in documentation for expand-import, expand-export and pre-expand-export
* Corrected typo in documentation for "for".
* Fixed error message for function which seems to have been renamed in the docs
* Fixed typo in a comment in the tests
* Fixed a typo in the documentation for set-subtract.
* Use double ellipses for the free-id-table-set*, free-id-table-set*!, bound-id-table-set* and bound-id-table-set*! operations
The optimizer assumed a fixnum result if either argument to
`bitwise-and` implies a fixnum result. That's not correct if the
fixnum agument is negative.
Thanks to Peter Samarin for a bug report.
Merge to v6.7
When calling a procedure that is attached as a
`prop:rename-transformer` property value, make sure that
any available expansion context is accessible as reflected by
`(syntax-transforming?)`.
Syntax parameters as rename transformers particularly rely on that
information for local expansion.
Thanks to Jay for the "stxparam.rktl" test.
Closes#1479
In a pattern like
a*b
a naive attempt to match will take quadratic time on an input that
contains all "a"s an no "b". To improve that case, the regexp compiler
detects that a match will require a "b" and checks the input for a "b"
to enable linear-time failure.
That optimization mishandled `(?!...)` and `(?<!...)` patterns,
treating the must-not-match subpatterns as things that must match.
So,
(regexp-match "a*(?!b)" "aaaxy")
returned false, because the input doesn't contain "b".
Thie commit repairs the optimization.
Closes#1468
Fix a regression relative to v6.4 caused by a refactoring of the
compiler between v6.4 and v6.5. The refactoring lost information about
letrecs that are converted internally to let* when a mutable variable
is involved, and it ends up allocating a closure before the box of a
mutable variable that is referenced by the closure. Something like
`with-continuation-mark` is needed around the closure's `lambda` to
prevent other optimizations from hiding the bug.
Closes#1462
