mappings:  make(map[mappingKey]*Mapping, len(srcs[0].Mapping)),
	}

	for _, src := range srcs {
		// Clear the profile-specific hash tables
		pm.locationsByID = makeLocationIDMap(len(src.Location))
		pm.functionsByID = make(map[uint64]*Function, len(src.Function))
		pm.mappingsByID = make(map[uint64]mapInfo, len(src.Mapping))

		if len(pm.mappings) == 0 && len(src.Mapping) > 0 {