it doesn't apply it the second time (since we know that the
only difference for indy blame is in the negative position
and we know that flat contracts never assign negative blame)
This commit combined with the two previous (2b9d855 and 003e8c7) do
not seem to have a significant effect on the performance of ->i
contract checking. In particular, I see a 50% slowdown between the
version before and the version after these commits on the third `time`
expression below, but no significant difference on the first two.
(without the improvement to flat-contract?, these commits are
a significant slowdown to `g`)
#lang racket
(require profile)
(define f
(contract (->i ([y () integer?]
[x (y) integer?])
(values [a () integer?]
[b (a) integer?]))
values
'pos 'neg))
(define g
(contract (->i ([y () (<=/c 10)]
[x (y) (>=/c y)])
(values [a () (<=/c 10)]
[b (a) (>=/c a)]))
values
'pos 'neg))
(define (slow-predicate n)
(cond
[(zero? n) #t]
[else (slow-predicate (- n 1))]))
(define h
(contract (->i ([y () slow-predicate]
[x (y) slow-predicate])
(values [a () slow-predicate]
[b (a) slow-predicate]))
values
'pos 'neg))
(time
(for ([x (in-range 100000)])
(f 1 2) (f 1 2) (f 1 2)
(f 1 2) (f 1 2) (f 1 2)
(f 1 2) (f 1 2) (f 1 2)))
(time
(for ([x (in-range 100000)])
(g 1 2) (g 1 2) (g 1 2)
(g 1 2) (g 1 2) (g 1 2)
(g 1 2) (g 1 2) (g 1 2)))
(time
(for ([x (in-range 10000)])
(h 50000 50000)))
When the main interpreter loop is called for an application where the
argument array coincides with the current runstack pointer, then the
protocol is that the callee gets to modify that space --- and it
should modify that space as arguments become unused. The interpreter
was always copying arguments to a fresh space, though.
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.
When parsing cannot fail, avoid allocating expectstacks and
failures (thanks samth for the idea). Allocation still happens
for progress and failuresets (conses of #t, now), though.
Compile with `PLTSTDERR="debug@syntax-parse"` to log cannot-fail
syntax-parse expressions and syntax class definitions.
Quote marks (at a minimum) should be triggered by any of the
characters in `atom-specials` from the IMAP RFC. The previous trigger
would not have worked for a password that includes parentheses, curly
braces, or an open quare bracket, for example.
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.
When caching the result of a stack traversal, adjust
the actual stack only after the traversal is complete
to avoid interfering with libunwind's decoding of the
stack.
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.
The continuation of a future being evaluated concurrently was not
correctly attributed to the future's custodian (as inherited from
from the creating thread).
One interesting corner case is when a vector is allocated
in a way that would exceed a memory limit. The custodian
captured with a future is used to guard large allocations.
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.
Make sure `#` is start at the start of the line using
the `IFDEF` function, although we'll probably never
again use a compiler old enough for this to matter.
