[llvm] [llvm-mca] Abort on parse error without -skip-unsupported-instructions (PR #90474)

[Andrea Di Biagio via llvm-commits]

adibiagio wrote:

> * llvm-mca today accepts bad input and prints analysis outputs.
> * It seems likely that was unintentional, but if anyone is relying on this, accidentally or otherwise, it would be nice to 'give them an out' if they need it.

I can tell you that it was not intentional. In case of parse errors, it leads to wrong/misleading perf reports. I may be wrong, but I don't think that this is what most users want. In general, I don't think that people should rely on this. 

As I mentioned in my previous message, we could add a separate option to specifically ignore parse errors.
When erroring out, we could print a remark message that says "Please use flag -XYZ` to explicitly ignore parse errors.`.
That way, people will know how to fix it if they get confused by this behaviour change.

Just my opinion.

https://github.com/llvm/llvm-project/pull/90474