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Tweak builtin symbol order for speed

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* lib-src/make-docfile.c (compare_globals):
Make symbols 1 through 4 be t, unbound, error, lambda.
This is in addition to symbol 0 being nil.
This change improved ‘make compile-always’ performance by 0.6%
on my platform.
This commit is contained in:
Paul Eggert 2019-07-11 23:06:22 -07:00
parent 77a4cc9f1a
commit 81a1088ee8
1 changed files with 16 additions and 5 deletions
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21
lib-src/make-docfile.c
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@ -641,13 +641,24 @@ compare_globals (const void *a, const void *b)
return ga->type - gb->type;
/* Consider "nil" to be the least, so that iQnil is zero. That
way, Qnil's internal representation is zero, which is a bit faster. */
way, Qnil's internal representation is zero, which is a bit faster.
Similarly, consideer "t" to be the second-least, and so forth. */
if (ga->type == SYMBOL)
{
bool a_nil = strcmp (ga->name, "Qnil") == 0;
bool b_nil = strcmp (gb->name, "Qnil") == 0;
if (a_nil | b_nil)
return b_nil - a_nil;
/* Common symbols in decreasing popularity order. */
static char const commonsym[][8]
= { "nil", "t", "unbound", "error", "lambda" };
int ncommonsym = sizeof commonsym / sizeof *commonsym;
int ai = ncommonsym, bi = ncommonsym;
for (int i = 0; i < ncommonsym; i++)
{
if (ga->name[0] == 'Q' && strcmp (ga->name + 1, commonsym[i]) == 0)
ai = i;
if (gb->name[0] == 'Q' && strcmp (gb->name + 1, commonsym[i]) == 0)
bi = i;
}
if (! (ai == ncommonsym && bi == ncommonsym))
return ai - bi;
}
return strcmp (ga->name, gb->name);