This page collects tools which may be useful to humans working on GHC.
Ben Gamari has a bunch of handy, albeit sometimes poorly documented, tools in his ghc-utils repository. These include the tools Ben uses for release management, day-to-day maintenance, performance characterization, and general GHC development. See the README for details.
Ben Gamari has developed hadrian-util, a handy wrapper for the Hadrian build system making several common workflows more convenient.
Joachim Breitner has developed the lovely gipeda web interface for comparing performance metrics between commits. This powers perf.haskell.org (with data from Joachim's ghc-speed-logs repository)