https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125706
Drea Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2026-06-10
Ever confirmed|0 |1
Keywords| |missed-optimization
Blocks| |85316
Severity|normal |enhancement
Status|UNCONFIRMED |NEW
--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
```
# RANGE [irange] int [100, 101] MASK 0x1 VALUE 0x64
_6 = (int) v5_i8_14(D);
# RANGE [irange] int [65, 80] MASK 0x1f VALUE 0x40
_7 = (int) v4_i8_13(D);
# RANGE [irange] int [0, 79] MASK 0x7f VALUE 0x0
_8 = _6 % _7;
```
Looks like the range of the mod is not as good as LLVM gets I think.
In this case:
the range is
[20, 35] union [21,36] or rather [20,36].
And then the range for the shift:
# RANGE [irange] int [6, 7] MASK 0x1 VALUE 0x6
_10 = (int) v2_u8_12(D);
# RANGE [irange] int [0, 1] MASK 0x1 VALUE 0x0
_11 = _9 >> _10;
Should be 0.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85316
[Bug 85316] [meta-bug] VRP range propagation missed cases
