[PATCH] CodeGen: Emit warnings when dropping profile data during PGO

[Duncan P. N. Exon Smith]

On Apr 10, 2014, at 15:53, Justin Bogner <mail at justinbogner.com> wrote:

> Bob Wilson <bob.wilson at apple.com> writes:
>> 
>> I know we had already discussed that warning name, but I’m now
>> wondering whether it should be “profile-instr-mismatch” to match the
>> command line options. What do you think?
> 
> After some thought, I think the parallel with the -f name is
> worthwhile. I've gone with profile-instr-dropped

I might be bike shedding here, but is -Wprofile-instr-out-of-date
better?  That matches the actual message you went with below.

Also, "dropped" still suggests a mismatch, whereas your new message
below talks about missing data as well.

Another possibility is to split those into two warnings.

 1. -Wprofile-instr-missing: warns about missing data.
 2. -Wprofile-instr-mismatch: warns about present but mismatched data.

>> This still doesn’t say much about what effect the mismatch may have or how to fix it. Maybe something like:
>> 
>> "mismatched profile data ignored for %0 of %1 function%s1; updating
>> the profile may improve optimizations”
> 
> This should be clearer:
> 
>  "profile data may be out of date: of %0 function%s0, %1 %plural{1:has|:have}1
>   no data and %2 %plural{1:has|:have}2 mismatched data that will be ignored"