Fix problem with once-use tracking and delayed variable-use marking
that is performed for local function bodies. A delayed variable-use
registration might happen after a once-used variable is replaced by
its use.
This scenario is difficult to provoke, because the optimizer has to
first decide not to move a once-use function, and in a latter pass
decide to move it after all. There's not enough information to
retract the tentative use plus its transitive implications.
The solution is to avoid the generic once-use layer for `lambda` forms
whose uses are delayed (and that likely has a good effect on inlining
anyway). The other half of the solution is to avoid transitive use
marking on a once-used variable whose expression has been moved (and
there are no transitive things to skip, because that expression isn't
a `lambda` form).
When the second argument to `bytes-set!` is a reference to a
module-level variable that is definitely defined but not a known
constant, then an incorrect reordering was used that would cause
the third argument value to get overwritten before the call.
Closes#1601
The primitive `read` uses a shortcut --- a private "ungetc"
implementation --- that did not count position correctly for
non-ASCII characters.
Closes#1599
The documentation says that it should work on any output port,
although there's special treatment of ports that originate
from `pretty-print` itself.
Closes#1579.
After some reductions, the new rator advance less the effect
clocks than the original rator. For example in
(equal? x 7) ==> (eq? x 7)
(my-struct? x) ==> #t or #f
The lambdas can be marked as single valued and/or mark preserving.
With this information is possible to remove unnecessary wrapping
like the `values` in
(let ([f (lambda () '(1))])
(display f f)
(values (f)))
or in reductions like
(car (list (f))) ==> (values (f)) ==> (f)
Moreover, this is useful to test that the optimizer has marked
correctly the function f as single valued and mark preserving.
If a module has any sort of complex bindings, such as a definition of
a macor-introduced identifiers, then `module->namespace` and variants
(like `variable-reference->namespace`) need to recreate suitable
bindings. Make sure that the module-path index for recreated bindings
is the run-time one, not the compile-time one.
Closes#1584
To avoid moving expressions that may have a side effect, the optimizer must
recognize that in this position this will cause an error and advance
the virtual clock.
Currently the only primitive that is flagged as SCHEME_PRIM_IS_OMITABLE and
may have multiple return values is `values`.
Thanks to Robby for finding the original version of the test.
When a hash table or other special value appears immediately on the
right-hand side of `define-values`, it needs to be protected by an
explicit quote when writing to bytecode.
Closes#1580
Continuing the saga that includes 8190a7730d and d1ba9fbb6e, it turns
out that a 0-binding clause as the last one isn't so special after
all. A little later in the optimizer, now that we're sometimes moving
an error to the body, we can't assume that the body can be discard
if an error was detected.
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.
