https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107822
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
CC| |aldyh at gcc dot gnu.org
Known to fail| |13.0
Known to work| |12.2.1
Ever confirmed|0 |1
Priority|P3 |P1
Last reconfirmed| |2022-12-21
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. Same with -O2.
Visiting conditional with predicate: if (c_13 != 0)
With known ranges
c_13: [irange] int [-INF, +INF] NONZERO 0x3
Predicate evaluates to: DON'T KNOW
Not folded
vs. handling the cycle PHI for c:
<bb 2> [local count: 118111600]:
b = 0;
goto <bb 4>; [100.00%]
<bb 3> [local count: 955630225]:
_1 = c_10 ^ 3;
_2 = b.1_3 + 1;
b = _2;
<bb 4> [local count: 1073741824]:
# c_10 = PHI <1(2), _1(3)>
b.1_3 = b;
if (b.1_3 <= 8)
goto <bb 3>; [89.00%]
else
goto <bb 5>; [11.00%]
<bb 5> [local count: 118111600]:
# c_13 = PHI <c_10(4)>
if (c_13 != 0)
Value ranges after VRP:
_1: int [1, 2]
c_2: int [1, 2]
this is yet another case where proper propagation is important. I'm
questioning the idea that on-demand ranger is a good solution and replacing
VRP1 was premature? I'm asking again as to what the plan was for cases like
this?
bit-CCP propagation arrives with
Simulating statement: c_10 = PHI <1(2), _1(3)>
Visiting PHI node: c_10 = PHI <1(2), _1(3)>
Argument #0 (2 -> 4 executable)
1 Value: CONSTANT 1
Argument #1 (3 -> 4 executable)
_1 Value: CONSTANT 0x0 (0x3)
PHI node value: CONSTANT 0x0 (0x3)
but it doesn't know that always either bit zero or one is set.
