https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67607
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2015-09-17
CC| |rguenth at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
so this is
((unsigned long)((unsigned int) length_4(D) - 1U) + 1)
you can't optimize this to (unsigned long) length_4(D) as for
length_4 == 0 the result is 0x100000000.
So what's the missed constant folding? Ah, so the above is guarded with
if (length_4(D) > 0)
which means we fail to optimize this to (unsigned long)length_4(D) because
we don't consider this transform might be valid when taking into account
range-info.
# RANGE [1, 2147483647] NONZERO 2147483647
_19 = (unsigned int) length_4(D);
# RANGE [0, 2147483646] NONZERO 2147483647
_18 = _19 + 4294967295;
# RANGE [0, 2147483646] NONZERO 2147483647
_21 = (sizetype) _18;
# RANGE [1, 2147483647] NONZERO 2147483647
_22 = _21 + 1;
so here VRP could for example have promoted _19 and _18 to sizetype. Or
it could handle the arithmetic simplification itself. We'd like to handle
(T)(X +- CST1) +- CST1
generally here (both widening/shortening casts).
