[Bug tree-optimization/110992] [14 Regression] Dead Code Elimination Regression at -O3 since r14-1654-g7ceed7e3e29
pinskia at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Thu Sep 14 21:22:25 GMT 2023
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110992
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
What we had before in GCC 13:
# RANGE [irange] unsigned short [0, 1] NONZERO 0x1
d.3_19 = (unsigned short) _3;
_21 = -d.3_19;
_22 = (short intD.17) _21;
_6 = (short intD.17) b.0_1;
_7 = _6 & _22;
Which then after r14-1654-g7ceed7e3e29 gives us:
_t = (short intD.17) d.3_19
_7 = _6 * _t
What we get after that match patch:
_3 = c.1_2 != 0;
_25 = (short intD.17) _3;
_22 = -_25;
_6 = (short intD.17) b.0_1;
_7 = _6 & _22;
That is we lose the range information.
If I add this to match.pd:
```
diff --git a/gcc/match.pd b/gcc/match.pd
index 97db0eb5f25..e68e2c57e25 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2181,6 +2181,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& (TYPE_UNSIGNED (type)
|| TYPE_PRECISION (type) > 1))))
+(match zero_one_valued_p
+ (convert@0 zero_one_valued_p@1))
+
/* Transform { 0 or 1 } * { 0 or 1 } into { 0 or 1 } & { 0 or 1 }. */
(simplify
(mult zero_one_valued_p@0 zero_one_valued_p@1)
```
Then this fails again.
I am thinking about adding this anyways so I am going to keep this one open.
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