[Bug target/116104] [15 Regression] GCN vs. "[rtl-optimization/116037] Explicitly track if a destination was skipped in ext-dce"

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116104

--- Comment #5 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Given the relatively unstructured nature of RTL and the error message, this is
almost certainly a bug in ext-dce.  I should have noted that when I assigned
the issue to myself.

I've been able to trip it with 20000629-1.c.  I don't expect it'll be hard to
fix at all.  Thanks.