[Bug c/110777] New: ice: SSA corruption

["dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110777

            Bug ID: 110777
           Summary: ice: SSA corruption
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

This C code 

int *findOrAddBackgroundInPalette_palette_pnm;
static void findOrAddBackgroundInPalette(unsigned *paletteSizeP,
                                    int *backgroundIndexP) {
  if (*paletteSizeP) {
    *backgroundIndexP = (*paletteSizeP)++;
    pm_message();
  }
  pm_message(findOrAddBackgroundInPalette_palette_pnm[*backgroundIndexP]);
}
void computeColorMap(int *backgroundIndexP) {
  unsigned paletteSize;
  findOrAddBackgroundInPalette(&paletteSize, backgroundIndexP);
}
int main() {
  unsigned backgroundIndex;
  _setjmp();
  computeColorMap(&backgroundIndex);
}

with recent gcc trunk, does this:

$ ~/gcc/results/bin/gcc -c -O3 -w ~/cvise/bug944.c

Unable to coalesce ssa_names 27 and 31 which are marked as MUST COALESCE.
paletteSize_27(ab) and  paletteSize_31(ab)
during RTL pass: expand
/home/dcb38/cvise/bug944.c: In function ‘main’:
/home/dcb38/cvise/bug944.c:14:5: internal compiler error: SSA corruption
   14 | int main() {
      |     ^~~~
0xf95b19 fail_abnormal_edge_coalesce(int, int)
        ../../trunk.year/gcc/tree-ssa-coalesce.cc:1003
0xf95b19 coalesce_partitions(_var_map*, ssa_conflicts*, coalesce_list*,
_IO_FILE*)
        ../../trunk.year/gcc/tree-ssa-coalesce.cc:1425


The bug first seems to occur sometime between g:b2cfe5233e682fc0
and g:f32518726ee8e836, a range of 30 commits.