https://llvm.org/bugs/show_bug.cgi?id=28551
Sebastian Pop <seb...@gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #9 from Sebastian Pop <seb...@gmail.com> ---
Which explains the crashes all over the place: the std::sort of today's libcxx
is inefficient as it calls the compare function on the same element:
// known that *(__i - 1) < *__m
// known that __i <= __m
while (true)
{
// __m still guards upward moving __i
while (__comp(*__i, *__m))
++__i;
// It is now known that a guard exists for downward moving __j
while (!__comp(*--__j, *__m))
;
if (__i > __j)
break;
swap(*__i, *__j);
++__n_swaps;
// It is known that __m != __j
// If __m just moved, follow it
if (__m == __i)
__m = __j;
++__i;
}
In particular this "if (__m == __i)" should be above the first call to
__comp().
Maybe some other places.
As the buildbots are not bootstrapping their libc++, there is not much I can do
to avoid all the users of Apple toolchains to see the assert failing.
I will remove the assert that I have in the GVNHoist code, and open a libcxx
bug for inefficiencies in the std::sort() algorithm.
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