https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |aldyh at gcc dot gnu.org,
| |jakub at gcc dot gnu.org
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Slightly cleaned up testcase:
static int b = 6, c;
long d;
short h, i, j;
signed char k;
void foo (void);
short baz (int, int, int, int, int, int, int);
short qux (unsigned short, int, char, long);
short
bar (short l, short m)
{
return l + m;
}
static signed char
corge (void)
{
unsigned n;
for (n = -10U; n >= 14; n = bar (n, 8))
{
i = qux (b, 0, c, b);
j = baz (i, b, d < j, 5, 7, 9, 5);
k = 200 + n;
h = k % 5;
if (!h)
foo ();
}
return n;
}
int
main ()
{
b || corge ();
b = 1;
}
The loop iterates twice, with n -10U and -2U, in third iteration 6U fails the
6U >= 14 condition.
In GCC 12 as well as in r13-439 and r13-440 the loop IV is
# ivtmp.30_42 = PHI <ivtmp.30_34(8), 190(7)>
and loop condition is
ivtmp.30_34 = ivtmp.30_42 + 8;
if (ivtmp.30_34 != 206)
while trunk has 2 IVs:
# RANGE [irange] unsigned int [38, 32767][4294934528, +INF] NONZERO
0xfffffffe
# n_32 = PHI <n_30(8), 4294967286(7)>
# RANGE [irange] unsigned int [1, +INF]
# ivtmp_2 = PHI <ivtmp_43(8), 2(7)>
and
# RANGE [irange] unsigned short [30, +INF] NONZERO 0xfffe
l.0_27 = (unsigned short) n_32;
# RANGE [irange] unsigned short [0, 7][38, +INF] NONZERO 0xfffe
_28 = l.0_27 + 8;
# RANGE [irange] short int [-INF, 7][38, +INF] NONZERO 0xfffe
_29 = (short int) _28;
# RANGE [irange] unsigned int [0, 7][38, 32767][4294934528, +INF] NONZERO
0xfffffffe
n_30 = (unsigned int) _29;
ivtmp_43 = ivtmp_2 - 1;
if (ivtmp_43 != 0)
The r13-440 regression is in vrp2, previously we were able to determine that
because ivtmp.30_42 is [190, 190][198, 198]
then (signed char) of that is [-66, -66][-58, -58] and that % 5 is [-3, -3][-1,
-1].
Folding statement: _24 = (signed char) ivtmp.30_42;
- Loops range found for ivtmp.30_42: unsigned char [190, 198] and calculated
range :unsigned char [190, 190][198, 205]
-Global Exported: _24 = signed char [-66, -58] ... irange was : signed char
[-66, -66][-58, -58]
+Global Exported: _24 = signed char [-66, -58]
Not folded
Folding statement: k = _24;
Not folded
Folding statement: _25 = _24 % 5;
-Global Exported: _25 = signed char [-3, -1] ... irange was : signed char [-3,
-3][-1, -1]
+Global Exported: _25 = signed char [-4, 0]
is the first difference in the vrp2 dump between r13-439 and r13-440.
The other major change is starting with r13-3486-g4c5b1160776382772 when ivopts
uses the 2 IVs rather than one
and the convoluted increment by 8. It is actually only a normal increment by 8
if n_32 is in [0, 32759][-32777U, -1U]
but that is actually the case here.
I think the ranger doesn't iterate, right? So is there any way that it would
figure out the exact range for the IV?
