[Bug rtl-optimization/115785] [15 regression] ICE when building embree-4.3.1 on amd64

[cvs-commit at gcc dot gnu.org]

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 <rsandifo@gcc.gnu.org>:

https://gcc.gnu.org/g:6e7053a641393211f52c176e540c8922288ab8db

commit r15-2008-g6e7053a641393211f52c176e540c8922288ab8db
Author: Richard Sandiford <richard.sandiford@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.