[Bug target/96808] New: MMA built-in dies with incorrect sharing of tree nodes error

[bergner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96808

            Bug ID: 96808
           Summary: MMA built-in dies with incorrect sharing of tree nodes
                    error
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bergner at gcc dot gnu.org
  Target Milestone: ---

bergner@pike:~/$ cat bug.c 
void
test (__vector_quad *dst, vector unsigned char vc)
{
  __vector_quad vq[2];
  __builtin_mma_xxsetaccz(&vq[1]);
  __builtin_mma_xvf32gerpp(&vq[1], vc, vc);
  *dst = vq[1];
}

bergner@pike:~/$ gcc -S -O2 -mcpu=power10 bug.c 
bug.c: In function ‘test’:
bug.c:2:1: error: incorrect sharing of tree nodes
    2 | test (__vector_quad *dst, vector unsigned char vc)
      | ^~~~
MEM[(__vector_quad *)&vq + 64B]
MEM[(__vector_quad *)&vq + 64B] = _4;
during GIMPLE pass: cfg
bug.c:2:1: internal compiler error: verify_gimple failed
0x11337297 verify_gimple_in_cfg(function*, bool)
        /home/bergner/gcc/gcc-fsf-mainline-bug/gcc/tree-cfg.c:5491
0x10ffb54f execute_function_todo
        /home/bergner/gcc/gcc-fsf-mainline-bug/gcc/passes.c:1992
0x10ff9da3 do_per_function
        /home/bergner/gcc/gcc-fsf-mainline-bug/gcc/passes.c:1640
0x10ffb867 execute_todo
        /home/bergner/gcc/gcc-fsf-mainline-bug/gcc/passes.c:2046
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

This is a bug in rs6000_gimple_fold_mma_builtin not expecting to handle an
array of accumulators.  Mine.  This dies on trunk and GCC 10.