https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110491
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Status|RESOLVED |ASSIGNED
Resolution|DUPLICATE |---
Last reconfirmed| |2023-07-04
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So the issue here is phiopt4 doing
<bb 6> [local count: 1073741824]:
- if (c_lsm_flag.14_16 != 0)
- goto <bb 8>; [66.67%]
- else
- goto <bb 7>; [33.33%]
-
- <bb 7> [local count: 357913944]:
-
- <bb 8> [local count: 1073741824]:
+ _26 = ~c_lsm_flag.14_16;
+ _14 = (int) _26;
# RANGE [irange] int [0, 1] NONZERO 0x1
- # prephitmp_27 = PHI <1(7), c_lsm.13_3(6)>
- c = prephitmp_27;
+ _4 = c_lsm.13_3 | _14;
+ c = _4;
return;
via
phiopt match-simplify trying:
c_lsm_flag.14_16 != 0 ? c_lsm.13_3 : 1
Matching expression match.pd:1991, gimple-match-5.cc:23
Matching expression match.pd:1991, gimple-match-5.cc:23
Matching expression match.pd:1991, gimple-match-5.cc:23
Matching expression match.pd:1948, gimple-match-7.cc:20
Matching expression match.pd:2480, gimple-match-4.cc:35
Matching expression match.pd:2483, gimple-match-3.cc:66
Matching expression match.pd:2490, gimple-match-2.cc:58
Applying pattern match.pd:6459, gimple-match-10.cc:12767
Applying pattern match.pd:1378, gimple-match-5.cc:7352
Applying pattern match.pd:1886, gimple-match-1.cc:1232
Applying pattern match.pd:4748, gimple-match-4.cc:15651
Folded into the sequence:
_13 = (int) c_lsm_flag.14_16;
_26 = ~c_lsm_flag.14_16;
_14 = (int) _26;
_4 = c_lsm.13_3 | _14;
Removing basic block 7
but
<bb 3> [local count: 9761289309]:
# RANGE [irange] int [0, 1] NONZERO 0x1
# c_lsm.13_3 = PHI <_17(D)(2), _11(5)>
so we have an uninitialized use here. The following fixes this.
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index 31a7c39e405..467c9fd108a 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -785,6 +785,13 @@ match_simplify_replacement (basic_block cond_bb,
basic_block middle_bb,
arg_false = arg0;
}
+ /* Do not make conditional undefs unconditional. */
+ if ((TREE_CODE (arg_true) == SSA_NAME
+ && ssa_name_maybe_undef_p (arg_true))
+ || (TREE_CODE (arg_false) == SSA_NAME
+ && ssa_name_maybe_undef_p (arg_false)))
+ return false;
+
tree type = TREE_TYPE (gimple_phi_result (phi));
result = gimple_simplify_phiopt (early_p, type, stmt,
arg_true, arg_false,
