#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by Bartosz Nitka <niteria@…>): In [changeset:"928d74733975fe4677e2b558d031779f58a0883c/ghc" 928d747/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="928d74733975fe4677e2b558d031779f58a0883c" Kill some unnecessary varSetElems When you do `varSetElems (tyCoVarsOfType x)` it's equivalent to `tyCoVarsOfTypeList x`. Why? If you look at the implementation: ``` tyCoVarsOfTypeList ty = runFVList $ tyCoVarsOfTypeAcc ty tyCoVarsOfType ty = runFVSet $ tyCoVarsOfTypeAcc ty ``` they use the same helper function. The helper function returns a deterministically ordered list and a set. The only difference between the two is which part of the result they take. It is redundant to take the set and then immediately convert it to a list. This helps with determinism and we eventually want to replace the uses of `varSetElems` with functions that don't leak the values of uniques. This change gets rid of some instances that are easy to kill. I chose not to annotate every place where I got rid of `varSetElems` with a comment about non-determinism, because once we get rid of `varSetElems` it will not be possible to do the wrong thing. Test Plan: ./validate Reviewers: goldfire, austin, simonmar, bgamari, simonpj Reviewed By: simonpj Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2115 GHC Trac Issues: #4012 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:145> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler