Weirdly enough even if I repro locally (by changing the DCHECK line to DCHECK_NE(desired_priority, THREAD_PRIORITY_ABOVE_NORMAL); which will hit).

|priority| is a bogus value "0n946859504 (No matching enumerant)" -- I do have the latest version of WinDBG but it seems to be at lost with the optimization at play here..?

FWIW, my build is Release + dcheck_always_on + component.

From the disassembly looks like the calling convention for |SetCurrentThreadPriority| is to put |priority| in ecx.

Maybe it later gets borked by the DCHECK/dump-without-crashing code as the value of |priority| is never used after the switch and the compiler could decide to re-use its register from that point on...?

I'll go ahead and assume we can't do anything about this specific instance as it's a compiler optimization taking precedence on debugability...

Yes, I think your analysis is correct. I don't see anywhere where ecx gets stored to the stack, so there's nothing to capture by the time it gets to grabbing a dump. Adding a base::debug::Alias(&priority) should force a stack spill, which should make it available.