3920e07f0b
Operand types are now tracked explicitly, so there is no need to reserve ID 0 for the special always-zero counter. As part of the renumbering, this change fixes an off-by-one error in the way counters were counted by the `coverageinfo` query. As a result, functions should now have exactly the number of counters they actually need, instead of always having an extra counter that is never used.
For more information about how rustc works, see the rustc dev guide.