#12274: GHC panic: simplifier ticks exhausted -------------------------------------+------------------------------------- Reporter: mrkkrp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: Compile-time | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by thomie): The problems start in the `Specialise` phase: {{{ # 7.8.4: # Result size of Simplifier = {terms: 62, types: 158, coercions: 1} # Result size of Specialise = {terms: 62, types: 158, coercions: 1} # # 7.10.3: # Result size of Simplifier = {terms: 66, types: 158, coercions: 1} # Result size of Specialise = {terms: 751, types: 2,319, coercions: 169} }}} * The output of `-ddump-spec` for `7.10` contains a list of `Local rules for imported ids`, but none for `7.8`. * The output of `-ddump-rule-firings` contains 326 rules for `7.10`, but only `20` for `7.8`. Some of the rule firings with `7.10`: {{{ Rule fired: Class op eof Rule fired: Class op fmap Rule fired: Class op fmap Rule fired: Class op $p1Stream Rule fired: Class op uncons Rule fired: Class op updatePos Rule fired: Class op updatePos Rule fired: Class op uncons Rule fired: Class op updatePos Rule fired: Class op updatePos Rule fired: Class op uncons Rule fired: Class op updatePos Rule fired: Class op updatePos Rule fired: Class op uncons Rule fired: Class op updatePos Rule fired: Class op updatePos Rule fired: SPEC/Test $fApplicativeParsecT @ Dec @ [Char] @ Identity Rule fired: SPEC/Test $fAlternativeParsecT @ Dec @ [Char] @ Identity Rule fired: Class op pure Rule fired: Class op pure ... ... ... }}} Here is a simplified example: Test.hs: {{{#!hs module Test where import A xs = mymap (+1) [1,2,3] }}} A.hs: {{{#!hs module A where mymap :: Functor f => (a -> b) -> f a -> f b mymap = fmap }}} ghc-7.8.4: {{{ $ ghc-7.8.4 Test.hs -ddump-rule-firings -O -fforce-recomp [1 of 2] Compiling A ( A.hs, A.o ) [2 of 2] Compiling Test ( Test.hs, Test.o ) Rule fired: Class op + Rule fired: Class op fmap Rule fired: map Rule fired: mapList }}} ghc-7.10.3: {{{ $ ghc-7.10.3 Test.hs -ddump-rule-firings -O -fforce-recomp [1 of 2] Compiling A ( A.hs, A.o ) [2 of 2] Compiling Test ( Test.hs, Test.o ) Rule fired: Class op + Rule fired: Class op fmap Rule fired: Class op fmap Rule fired: Class op fmap Rule fired: map Rule fired: mapList }}} Why does the `Class op fmap` fire three times with 7.10.3? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12274#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler