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acc: implement min_set() and max_set() using gcc builtins

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Fixes #238.

* spot/twa/acc.hh (max_set): Add a version using __builtin_clz().
(min_set): New method.
* tests/core/acc.cc, tests/core/acc.test: Add some tests.
This commit is contained in:
Alexandre Duret-Lutz 2017-03-02 14:17:06 +01:00
parent 22a3d1c393
commit 1eb5be543d
3 changed files with 42 additions and 7 deletions
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29
spot/twa/acc.hh
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@ -230,10 +230,13 @@ namespace spot
}
// Return the number of the highest set used plus one.
// So if no set is used, this returns 0,
// but if the sets {1,3,8} are used, this returns 9.
// If no set is used, this returns 0,
// If the sets {1,3,8} are used, this returns 9.
unsigned max_set() const
{
#ifdef __GNUC__
return (id == 0) ? 0 : (sizeof(unsigned) * 8 - __builtin_clz(id));
#else
auto i = id;
int res = 0;
while (i)
@ -242,6 +245,28 @@ namespace spot
i >>= 1;
}
return res;
#endif
}
// Return the number of the lowest set used plus one.
// If no set is used, this returns 0.
// If the sets {1,3,8} are used, this returns 2.
unsigned min_set() const
{
if (id == 0)
return 0;
#ifdef __GNUC__
return __builtin_ctz(id) + 1;
#else
auto i = id;
int res = 1;
while ((i & 1) == 0)
{
++res;
i >>= 1;
}
return res;
#endif
}
// Return the lowest acceptance mark