[Bug c/120921] New: gimple verifier (and gimple FE) accepts CST on LHS

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120921

            Bug ID: 120921
           Summary: gimple verifier (and gimple FE) accepts CST on LHS
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid, ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
            Blocks: 101057
  Target Milestone: ---

Take:
```
void __GIMPLE b(int t) {
  1 = t;
}
```

This should verify as being invalid but the gimple verifiers accept the code
and then we run into an ICE. Basically any CST on the LHS is accepted.

This is different from PR 120913 where the ICE happens earlier than when the
verifiers happen, the ICE here happens during expand.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101057
[Bug 101057] [meta-bug] [gimplefe] GIMPLE frontend issues