* Re: scratch/bytecode-speedup 870806d4c4 04/11: Pin bytecode strings to avoid copy at call time
[not found] ` <20220111165048.75C05C0DA31@vcs2.savannah.gnu.org>
@ 2022-01-11 17:09 ` Stefan Monnier
0 siblings, 0 replies; 2+ messages in thread
From: Stefan Monnier @ 2022-01-11 17:09 UTC (permalink / raw)
To: emacs-devel; +Cc: Mattias Engdegård
> branch: scratch/bytecode-speedup
> commit 870806d4c453addca794aa0940298425241e13d9
> Author: Mattias Engdegård <mattiase@acm.org>
> Commit: Mattias Engdegård <mattiase@acm.org>
>
> Pin bytecode strings to avoid copy at call time
> + /* ... we plonk BYTESTR and VECTOR there to ensure that they survive
> + GC (bug#33014), since these variables aren't used directly beyond
> + the interpreter prologue and wouldn't be found in the stack frame
> + otherwise. */
> + stack_base[0] = bytestr;
> + stack_base[1] = vector;
> + Lisp_Object *top = stack_base + 1;
> + Lisp_Object *stack_lim = top + stack_items;
> + unsigned char const *bytestr_data = SDATA (bytestr);
Why not keep a ref to the function object itself?
That would also allow providing a new bytecode to extract a `self`
reference to the function that's being executed.
Oh, I think I can see one reason: there's no such object when we're
called from `Fbyte_code`. Maybe `Fbyte_code` should be reimplemented as
`(funcall (make-byte-code 0 bytecode csts depth))`?
(and change `bytecomp.el` not to use `byte-code` any more)
(and mark `byte-code` as obsolete)
Stefan
^ permalink raw reply [flat|nested] 2+ messages in thread
[parent not found: <20220111165050.357D6C0DA35@vcs2.savannah.gnu.org>]
* Re: scratch/bytecode-speedup 1dca615cf9 08/11: Move a runtime interpreter check to ENABLE_CHECKING
[not found] ` <20220111165050.357D6C0DA35@vcs2.savannah.gnu.org>
@ 2022-01-11 17:22 ` Stefan Monnier
0 siblings, 0 replies; 2+ messages in thread
From: Stefan Monnier @ 2022-01-11 17:22 UTC (permalink / raw)
To: Mattias Engdegård; +Cc: emacs-devel
> + /* The byte code should have been properly pinned. */
> eassert (SDATA (bytestr) == bytestr_data);
> -
> /* Binds and unbinds are supposed to be compiled balanced. */
> - if (SPECPDL_INDEX () != count)
> - {
> - if (SPECPDL_INDEX () > count)
> - unbind_to (count, Qnil);
> - error ("binding stack not balanced (serious byte compiler bug)");
> - }
> + eassert (SPECPDL_INDEX () == count);
This makes compiler debugging harder since it crashes Emacs instead of
signaling a clean error :-(
Maybe this actually should not be an error at all, and instead
`bytecomp.el` could skip emitting trailing `unbind`s and rely on
`exec_byte_code` doing the unbinds instead.
I think this would result in a speed up (and a more compact bytecode)
with dynbind code. Not sure how it'd work out with lexbind code where
it's much more common for functions not to need any `unbind`.
Stefan
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2022-01-11 17:09 ` scratch/bytecode-speedup 870806d4c4 04/11: Pin bytecode strings to avoid copy at call time Stefan Monnier
[not found] ` <20220111165050.357D6C0DA35@vcs2.savannah.gnu.org>
2022-01-11 17:22 ` scratch/bytecode-speedup 1dca615cf9 08/11: Move a runtime interpreter check to ENABLE_CHECKING Stefan Monnier
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