https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115785
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Richard Sandiford <rsand...@gcc.gnu.org>: https://gcc.gnu.org/g:6e7053a641393211f52c176e540c8922288ab8db commit r15-2008-g6e7053a641393211f52c176e540c8922288ab8db Author: Richard Sandiford <richard.sandif...@arm.com> Date: Fri Jul 12 15:50:36 2024 +0100 rtl-ssa: Fix prev_any_insn [PR115785] Bit of a brown paper bag issue, but: due to the representation of the insn chain, insn_info::prev_any_insn would sometimes skip over instructions. This led to an invalid update in the PR when adding and removing instructions. I think one of the reasons I failed to spot this when checking the code is that m_prev_insn_or_last_debug_insn is misnamed: it's the previous instruction *of the same type* or the last debug instruction in a group. The patch therefore renames it to m_prev_sametype_or_last_debug_insn (with the term prev_sametype already being used in some accessors). The reason this didn't show up earlier is that (a) prev_any_insn is rarely used directly, (b) no instructions were lost from the def-use chains, and (c) only consecutive debug instructions were skipped when walking the insn chain. The chaining scheme makes prev_any_insn more complicated than next_any_insn, prev_nondebug_insn and next_nondebug_insn, but the object code produced is still relatively simple. gcc/ PR rtl-optimization/115785 * rtl-ssa/insns.h (insn_info::prev_insn_or_last_debug_insn) (insn_info::next_nondebug_or_debug_insn): Remove typedefs. (insn_info::m_prev_insn_or_last_debug_insn): Rename to... (insn_info::m_prev_sametype_or_last_debug_insn): ...this. * rtl-ssa/internals.inl (insn_info::insn_info): Update after above renaming. (insn_info::copy_prev_from): Likewise. (insn_info::set_prev_sametype_insn): Likewise. (insn_info::set_last_debug_insn): Likewise. (insn_info::clear_insn_links): Likewise. (insn_info::has_insn_links): Likewise. * rtl-ssa/member-fns.inl (insn_info::prev_nondebug_insn): Likewise. (insn_info::prev_any_insn): Fix moves from non-debug to debug insns. gcc/testsuite/ PR rtl-optimization/115785 * g++.dg/torture/pr115785.C: New test.
