https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43892
--- Comment #33 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #32)
> So it is more about the back-end of PowerPC at this point.
For the testcase
===
typedef unsigned int u32;
typedef unsigned long long u64;
u32 f(u32 a, u32 b)
{
u32 s = a + b;
if (a + b < b)
s++;
return s;
}
u32 g(u32 *p, u32 n)
{
u32 s = 0;
while (n--)
s = f(s, *p++);
return s;
}
u32 g4(u32 *p)
{
u32 s = 0;
s = f(s, *p++);
s = f(s, *p++);
s = f(s, *p++);
s = f(s, *p++);
return s;
}
u32 h4(u32 *p)
{
u64 s = 0;
s += *p++;imple
s += *p++;
s += *p++;
s += *p++;
s = (s >> 32) + (u32)s;
s = (s >> 32) + (u32)s;
return s;
}
===
... GCC does not do anything with ADD_OVERFLOW. But all *do* compile
to reasonable code (albeit not optimal). So no, you cannot say Gimple
is super here and it is all the backend's fault :-)
