https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82732
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
We do recognize the memset early enough. What we fail to recognize is that the
size argument to malloc is the same as the length of the memset:
_1 = (long unsigned int) size_8(D);
_2 = _1 * 4;
p_11 = malloc (_2);
if (size_8(D) != 0)
goto <bb 3>; [85.00%] [count: INV]
else
goto <bb 4>; [15.00%] [count: INV]
<bb 3> [12.75%] [count: INV]:
_18 = size_8(D) + 4294967295;
_21 = (sizetype) _18;
_7 = _21 + 1;
_6 = _7 * 4;
__builtin_memset (p_11, 0, _6);
VRP could be taught to simplify (unsigned long)(u-1)+1 to (unsigned long)u for
unsigned int u non-zero (though there is no VRP between ldist and strlen), or
we could try to generate some simpler code in ldist...
