#13536: Program which terminates instantly in GHC 8.0.2 runs for minutes with 8.2.1 -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * cc: nomeata (added) Comment:
The culprit is apparently the new STG CSE pass
Ah yes! We very carefully run a final demand-analysis just before tidy- core, precisely to ensure that the used-once info (which can get invalidated) is correct before code gen. But the STG CSE pass is undoing that goodness. Total disaster. I'll think about how best to do this. Copying Joachim who added CSE for STG> -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13536#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler