[Bug tree-optimization/108095] powerpc-linux / powerpc64-linux: ICEs when building Linux's arch/powerpc/kernel/align.c (asm goto)

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108095

--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:7e54e5a2bba69dc7fcbc88fe8cb20c91aaafabd2

commit r12-9126-g7e54e5a2bba69dc7fcbc88fe8cb20c91aaafabd2
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Dec 15 09:26:44 2022 +0100

    into-ssa: Fix emitting debug stmts after asm goto [PR108095]

    The following testcase ICEs, because ccp1 replaced
      s.0_1 = &s;
      __asm__ goto("" : "=r" MEM[(T *)s.0_1] :  :  : "lab" lab);
    with
      __asm__ goto("" : "=r" s :  :  : "lab" lab);
    and because s is no longer addressable, we are rewriting it into
    ssa and want
      __asm__ goto("" : "=r" s_7 :  :  : "lab" lab);
    plus debug stmt
      # DEBUG s => s_7
    The code assumes that there is at most one non-EH edge in that
    case, but with the addition of outputs to asm goto that is no longer the
    case, we can have many outgoing edges.

    The patch keeps the checking assertion that there is at most one such
    edge for everything but asm goto, but moves the addition of the debug
    stmt into the loop, so that it can be added on all edges where it is
    possible, not just one of them.

    Furthermore, looking at gsi_insert_on_edge_immediate
    -> gimple_find_edge_insert_loc, the conditions to insert stmt there
    to the destination block are
      if (single_pred_p (dest)
          && gimple_seq_empty_p (phi_nodes (dest))
          && dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
    (plus there is code to insert it in the previous block but that is
    never true when the pred is known to be stmt_ends_bb_p), while
    mayube_register_def was just checking
                     if (ef && single_pred_p (ef->dest)
                         && ef->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
    so if for whatever reason ef->dest had any PHIs, we'd split the
    edge for -g and not for -g0, something we must avoid for -fcompare-debug
    stability.  So, I've added the no phi_nodes check too.

    2022-12-15  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/108095
            * tree-into-ssa.cc (maybe_register_def): Insert debug stmt
            on all non-EH edges from asm goto if they have a single
            predecessor rather than asserting there is at most one such edge.
            Test whether there are no PHI nodes next to the single predecessor
            test.

            * gcc.dg/pr108095.c: New test.

    (cherry picked from commit bf3ce6f84a7a994a0fc87419b383b9ce4efed442)