https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109311
Bug ID: 109311
Summary: [13 Regression] bb_is_just_return miss to realize some
bb from r13-6873-g776a5bb5894315
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: linkw at gcc dot gnu.org
Target Milestone: ---
Commit r13-6873-g776a5bb5894315 changed BB insns walking order under the
assumption that the handlings in the loop is order independent. But
unfortunately some failures shows it's not.
For a BB:
15: L15:
20: NOTE_INSN_BASIC_BLOCK 5
19: use %3:SI
32: NOTE_INSN_EPILOGUE_BEG
33: simple_return
;; succ: EXIT
Previously function bb_is_just_return would return true while now it returns
false, since backward walking will meet return insn first, the USE insn isn't
considered as one use to be in *use but instead is taken as unexpected insn
then return false.
By adjusting it not to check !*ret for use can workaround it,
if (!*ret && ANY_RETURN_P (pat))
*ret = insn;
- else if (!*ret && !*use && GET_CODE (pat) == USE
+ else if (!*use && GET_CODE (pat) == USE
&& REG_P (XEXP (pat, 0))
&& REG_FUNCTION_VALUE_P (XEXP (pat, 0)))
*use = insn;
but I'm not sure if there is some reason to check both !*ret && !*use, such as
to exclude something like:
simple_return
use %3:SI
