#9565: T3500b exhaust simplifier ticks (loops?) on WAY=optasm -------------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: x86_64 (amd64) | Unknown/Multiple Difficulty: Unknown | Type of failure: Compile- Blocked By: | time crash Related Tickets: | Test Case: T3500b | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- {{{ $ make fulltest TEST="T3500b" WAY=optasm =====> T3500b(optasm) 3767 of 4101 [0, 0, 0] cd ./typecheck/should_run && '/home/slyfox/dev/git/ghc- validate/inplace/bin/ghc-stage2' -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db -rtsopts -fno-ghci-history -o T3500b T3500b.hs -O -fasm >T3500b.comp.stderr 2>&1 Compile failed (status 256) errors were: [1 of 1] Compiling Main ( T3500b.hs, T3500b.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 7.9.20140907 for x86_64-unknown-linux): Simplifier ticks exhausted When trying RuleFired foldr/augment To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 12441 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Attempt to increase '''-fsimpl-tick-factor''' does not help copiling sample. Looks like infinite inlining pass. The test source itself: {{{#!hs {-# LANGUAGE TypeFamilies, FlexibleContexts, UndecidableInstances #-} module Main where newtype Mu f = Mu (f (Mu f)) type family Id m type instance Id m = m instance Show (Id (f (Mu f))) => Show (Mu f) where show (Mu f) = show f showMu :: Mu (Either ()) -> String showMu = show item :: Mu (Either ()) item = Mu (Right (Mu (Left ()))) main = print (showMu item) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9565 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler