* Re: [Emacs-diffs] feature/byte-switch 7c2d493: src/bytecode.c: Add optional sanity check for jump tables.
[not found] ` <20170211144459.A837B2319A@vcs0.savannah.gnu.org>
@ 2017-02-11 15:51 ` Stefan Monnier
2017-02-11 17:48 ` Vibhav Pant
0 siblings, 1 reply; 3+ messages in thread
From: Stefan Monnier @ 2017-02-11 15:51 UTC (permalink / raw)
To: emacs-devel; +Cc: Vibhav Pant
> + /* Hash tables for switch are declared with :size set to the
> + exact number of cases. */
> + if (BYTE_CODE_SAFE)
> + eassert (HASH_TABLE_SIZE (h) == h->count);
Why should we force this constraint on the code that generates the
hash-tables. I think this is wrong. We just need a comment that
explains that we use h->count as a faster approximation of
HASH_TABLE_SIZE(h) (and BTW, the comment belongs next to the relevant
code which is not the `for` loop but the "if (h->count <= 5)" test) and
that we hence leave it to the bytecompiler to ensure that this
approximation is good enough.
Stefan
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Emacs-diffs] feature/byte-switch 7c2d493: src/bytecode.c: Add optional sanity check for jump tables.
2017-02-11 15:51 ` [Emacs-diffs] feature/byte-switch 7c2d493: src/bytecode.c: Add optional sanity check for jump tables Stefan Monnier
@ 2017-02-11 17:48 ` Vibhav Pant
2017-02-11 19:50 ` Stefan Monnier
0 siblings, 1 reply; 3+ messages in thread
From: Vibhav Pant @ 2017-02-11 17:48 UTC (permalink / raw)
To: Stefan Monnier; +Cc: emacs-devel@gnu.org
On Sat, Feb 11, 2017 at 9:21 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> + /* Hash tables for switch are declared with :size set to the
>> + exact number of cases. */
>> + if (BYTE_CODE_SAFE)
>> + eassert (HASH_TABLE_SIZE (h) == h->count);
>
> Why should we force this constraint on the code that generates the
> hash-tables. I think this is wrong.
Also, the rationale for putting a constraint on the :size of the hash
table was that it would save pure storage if the function (and thus
the jump table in the constant vector) was purecopied.
--
Vibhav Pant
vibhavp@gmail.com
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Emacs-diffs] feature/byte-switch 7c2d493: src/bytecode.c: Add optional sanity check for jump tables.
2017-02-11 17:48 ` Vibhav Pant
@ 2017-02-11 19:50 ` Stefan Monnier
0 siblings, 0 replies; 3+ messages in thread
From: Stefan Monnier @ 2017-02-11 19:50 UTC (permalink / raw)
To: emacs-devel
> Also, the rationale for putting a constraint on the :size of the hash
> table was that it would save pure storage if the function (and thus
> the jump table in the constant vector) was purecopied.
But that's also a mere optimisation. Not something whose absence
deserves an abort.
Stefan
^ permalink raw reply [flat|nested] 3+ messages in thread
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[not found] ` <20170211144459.A837B2319A@vcs0.savannah.gnu.org>
2017-02-11 15:51 ` [Emacs-diffs] feature/byte-switch 7c2d493: src/bytecode.c: Add optional sanity check for jump tables Stefan Monnier
2017-02-11 17:48 ` Vibhav Pant
2017-02-11 19:50 ` Stefan Monnier
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