ghc documentation doesn't explain difference between dwarf levels 1 2 and 3

I tried digging into current ghc source (well a 8.6.2 checkout) to track down where / how debugLevel crops up.

The docs/examples support g0 (off ) through g3. But when looking at where debugLevel appears in code, there isn't any different currently at the GHC layer for g3 vs g2! (is there a difference at the C compiler layer?)

Trac metadata

Trac field	Value
Version	8.6.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Documentation
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changed milestone to %8.6.3

changed weight to 5

added Tbug Trac import documentation labels

Ticket retargeted after milestone closed

added debug information label

added Pnormal label