https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126879
Bug ID: 126879
Summary: match pattern for `(a ^ b) cmp c || a != b`/`(a ^ b)
cmp c && a == b` has non-needed tree_expr_nonzero_p on
it
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: easyhack, missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Created attachment 65337
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65337&action=edit
testcase
For the testcase we should produce the same results at -O1. But current does
not because the patterns for `(a ^ b) cmp c || a != b`/`(a ^ b) cmp c && a ==
b` current has a tree_expr_nonzero_p on it:
```
/* ((a ^ b) & c) cmp d || a != b --> (0 cmp d || a != b). */
/* ((a ^ b) & c) cmp d && a == b --> (0 cmp d && a == b). */
(for bitop (bit_ior bit_and)
neeq (ne eq)
(for cmp (simple_comparison)
(simplify
(bitop:c
(cmp:c
(bit_and:c
(bit_xor @0 @1)
tree_expr_nonzero_p@2)
@3)
(neeq@4 @0 @1))
(bitop
(cmp
{ build_zero_cst (TREE_TYPE (@0)); }
@3)
@4))
```
the nonzero is not needed here as `a^b` will be zero in the case of knowing
`a==b`.
