[llvm] [Support] report_fatal_error: Do not generate crash backtrace by default (PR #128495)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

> There are a range of cases where the meaning of "invalid" and "input to the compiler" are not clear. abort-with-backtrace is not appropriate.

This is fine: 1) IMO it should be a minority and 2) it should be a conscious decision of the developer, hence an opt-in.
Changing the default is not the right option as it affects the majority of cases where we shouldn't crash and report proper errors when needed (as library should).

> There are also cases which cannot or should not be promoted to IR verifier error, and still need some kind of minimal effort to avoid a crash in the backend.

I don't follow how "minimal effort avoiding a crash in the backend" isn't just pointing to a compiler bug? 

https://github.com/llvm/llvm-project/pull/128495