[Bug tree-optimization/126947] New: [15/16/17 Regression] ICE Unable to coalesce ssa_names 4 and 8 which are marked as MUST COALESCE.

[ktkachov at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126947

            Bug ID: 126947
           Summary: [15/16/17 Regression] ICE Unable to coalesce ssa_names
                    4 and 8 which are marked as MUST COALESCE.
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

int _setjmp (int);
void escape (void);

int
f (int flags)
{
  int lo = (flags >> 4) & 7, hi = (flags >> 8) & 3;
  escape ();
  _setjmp (flags);
  if (lo == 5)
    if (hi == 2)
      flags &= 0;
  escape ();
  return flags;
}

ICEs on aarch64 at -O2:

Unable to coalesce ssa_names 4 and 8 which are marked as MUST COALESCE.
flags_4(ab) and  flags_8(D)(ab)
during RTL pass: expand
<source>: In function 'f':
<source>:5:1: internal compiler error: SSA corruption
    5 | f (int flags)
      | ^