[GHC] #14170: 8.2.1 regression: GHC fails to simplify `natVal`
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When GHC 8.2.1 compiles this code with `-O`: {{{#!hs {-# LANGUAGE TypeApplications #-} {-# LANGUAGE TypeInType #-} module NatVal where import Data.Proxy import GHC.TypeLits foo = natVal $ Proxy @0 }}} it produces the following Core: {{{#!hs -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0} NatVal.foo1 :: Integer NatVal.foo1 = 0 -- RHS size: {terms: 41, types: 18, coercions: 0, joins: 0/0} foo :: Integer foo = case NatVal.foo1 of wild_a1iV { integer-gmp-1.0.1.0:GHC.Integer.Type.S# i#_a2ke -> case GHC.Prim.tagToEnum# @ Bool (GHC.Prim.>=# i#_a2ke 0#) of { False -> case GHC.Natural.underflowError of wild2_00 { }; True -> integer-gmp-1.0.1.0:GHC.Integer.Type.wordToInteger (GHC.Prim.int2Word# i#_a2ke) }; integer-gmp-1.0.1.0:GHC.Integer.Type.Jp# dt_a2km -> case GHC.Prim.uncheckedIShiftRL# (GHC.Prim.sizeofByteArray# dt_a2km) 3# of { __DEFAULT -> case GHC.Prim.sizeofByteArray# dt_a2km of { __DEFAULT -> wild_a1iV; 0# -> case GHC.Natural.underflowError of wild4_00 { } }; 1# -> case GHC.Prim.indexWordArray# dt_a2km 0# of wild2_a2kq { __DEFAULT -> integer-gmp-1.0.1.0:GHC.Integer.Type.wordToInteger wild2_a2kq } }; integer-gmp-1.0.1.0:GHC.Integer.Type.Jn# ipv_a2kt -> case GHC.Natural.underflowError of wild1_00 { } } }}} while GHC-8.0.1 does the right thing: {{{#!hs -- RHS size: {terms: 1, types: 0, coercions: 0} foo :: Integer foo = 0 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I was able to track this down to commit 1fcede43d2b30f33b7505e25eb6b1f321be0407f (`Introduce GHC.TypeNats module, change KnownNat evidence to be Natural`), which hints at the problem. In that commit, we switched the internal representation of `Nat`s from `Integer`s to `Natural`s (from `Numeric.Natural`). For whatever reason, however, `Natural` values don't seem to simplify as well as `Integers`, as evidenced by this simpler program: {{{#!hs module Bug where import Numeric.Natural foo :: Natural foo = 0 }}} which also produces essentially identical core: {{{#!hs -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0} Bug.foo1 :: Integer [GblId, Caf=NoCafRefs, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 100 0}] Bug.foo1 = 0 -- RHS size: {terms: 39, types: 12, coercions: 0, joins: 0/0} foo :: Natural [GblId, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=False, ConLike=False, WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 126 60}] foo = case Bug.foo1 of { integer-gmp-1.0.1.0:GHC.Integer.Type.S# i#_a2bZ -> case GHC.Prim.tagToEnum# @ Bool (GHC.Prim.>=# i#_a2bZ 0#) of { False -> GHC.Natural.underflowError @ Natural; True -> GHC.Natural.NatS# (GHC.Prim.int2Word# i#_a2bZ) }; integer-gmp-1.0.1.0:GHC.Integer.Type.Jp# dt_a2c9 -> case GHC.Prim.uncheckedIShiftRL# (GHC.Prim.sizeofByteArray# dt_a2c9) 3# of { __DEFAULT -> case GHC.Prim.sizeofByteArray# dt_a2c9 of { __DEFAULT -> GHC.Natural.NatJ# dt_a2c9; 0# -> GHC.Natural.underflowError @ Natural }; 1# -> case GHC.Prim.indexWordArray# dt_a2c9 0# of wild2_a2cd { __DEFAULT -> GHC.Natural.NatS# wild2_a2cd } }; integer-gmp-1.0.1.0:GHC.Integer.Type.Jn# ipv_a2cg -> GHC.Natural.underflowError @ Natural } }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): OK here's the deal. * In the olden days we represented in `Integer` literal, say 3, in Core by `S# 3#`; that is, we exposed its reprsentation. That made constant folding of `plusInteger 3 5` hard, becuase it meant inlining `plusInteger` which is remarkably big. Result: tons of useless clutter. * Nowadays an `Integer` literal, say 3, is represented in GHC by `Lit (LitInteger 3)`, and ''not'' by an application of the data constructor `S#`. This latter expansion is done right at the end, by `CorePrep`. * That makes constant-folding, like `3+4` rewriting to `7` much, much easier. * We refrain from inlining things like `plusInteger`, `negateInteger` etc until a later stage, and instead add constant-folding rwerite rules for each of these functions. By delaying inlining, the constant-folding rewrite rules (all in `compiler/prelude/PrelRules`) have a decent chance to fire first. * However, in introducing `Natural` we failed to do any of this. The code {{{ foo :: Natural foo = 0 }}} turns into `foo = naturalFromInteger (0::Integer)`, and `naturalFromInteger` has an INLINE pragma. The right thing is presumably to treat `Natural` just like we treat `Integer`: * Keep it as a `LitInteger`. Conveniently `LitInteger` already stores its type, so we can distinguish literal integers from naturals. * Expand the literal in `CorePrep`. * Delay the inlining of `Natural` operations. * Add constant-folding rewrite rules to `PrelRules` I suppose we could also consider making `exprIsConApp_maybe` on an `Integer` literal return `S# n` or whatnot; just possibly that'd be useful anyway, but only for funcions that lack a constant-fold rewrite rule. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): I'm not really sure representing `Integer` and `Natural` is a great idea. Afterall, we then need to painstakingly evaluate all of the constant folding rules to ensure we don't, for instance, rewrite `(5 - 9) :: Natural` to `-4`. Moreover, distinguishing `Integer` `LitIntegers` from `Natural` `LitIntegers` on the basis of type alone would mean that `CorePrep` will need to do a type comparison in `cpeRhsE` instead of just deciding on the basis of which `Literal` constructor was used. In sum, I suspect `Integer` and `Natural` are just different enough to warrant separate constructors. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * milestone: 8.2.2 => 8.2.3 Comment: Regardless, it doesn't look like this is going to happen for 8.2.2. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by Bodigrim): * cc: Bodigrim (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Bodigrim): I am interested in this issue due to #14465. I tried to prepare a patch Phab:D4212, but stumbled upon a build issue. Can someone please explain what went wrong? Sorry, I am new to GHC build system. {{{ "inplace/bin/ghc-stage1" -hisuf hi -osuf o -hcsuf hc -static -O0 -H64m -Wall -this-unit-id base-4.11.0.0 -hide-all-packages -i -ilibraries/base/. -ilibraries/base/dist-install/build -Ilibraries/base /dist-install/build -ilibraries/base/dist-install/build/./autogen -Ilibraries/base/dist-install/build/./autogen -Ilibraries/base/include -optP-DOPTIMISE_INTEGER_GCD_LCM -optP-include -optPlibraries/base/dist- install/build/./autogen/cabal_macros.h -package-id rts -package-id ghc- prim-0.5.2.0 -package-id integer-gmp-1.0.1.0 -this-unit-id base -XHaskell2010 -O -no-user-package-db -rtsopts -Wno-trustworthy-safe -Wno-deprecated-flags -Wnoncanonical-monad-instances -odir libraries/base/dist-install/build -hidir libraries/base/dist-install/build -stubdir libraries/base/dist-install/build -dynamic-too -c libraries/base/./GHC/Natural.hs -o libraries/base/dist- install/build/GHC/Natural.o -dyno libraries/base/dist- install/build/GHC/Natural.dyn_o <interactive>:1:1: error: Bad interface file: libraries/base/dist-install/build/GHC/Natural.hi libraries/base/dist-install/build/GHC/Natural.hi: openBinaryFile: does not exist (No such file or directory) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Have you tried cleaning your tree? It looks like the build system neglected to build that interface file (which is a bit perplexing, but stranger things have happened with the `make` build system). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by Bodigrim): * owner: (none) => Bodigrim Comment: I'll continue with my patch this weekend, sorry for long delay. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mpickering): Could we not fix this by reverting 1fcede43d2b30f33b7505e25eb6b1f321be0407f ? Is there enough motivation to replace the evidence type? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * cc: phadej (added) Comment: We certainly wouldn't want to revert that commit in its entirety (if that is the route we decide to embark on)—besides changing the evidence type, that commit also reworked `base` a bit to export a different API in the form of the `GHC.TypeNats` module. We could conceivably change the evidence type and keep the new API, but it would take some care. To be honest, I'm inclined to just wait for Bodigrim's patch. After all, these changes are already in a released version of GHC—I'd rather wait slightly longer to get things right. (cc'ing phadej, who authored 1fcede43d2b30f33b7505e25eb6b1f321be0407f) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by phadej): Yes, IMO there is enough motivation to have evidence as `Natural`. We are talking about type level Nats, not Ints. The fact that term value `Natural`s are second-grade citizens in GHC atm is unfortunate. If we are able to constant fold other numeric types, we should be able to do that for `Natural` too. See https://phabricator.haskell.org/D3024 discussion. I'm in great favour of adding `Natural` literal into core. It was untrivial and I didn't pursue that back then, but again IMO it's the right thing to do. Pushing even further, I'd propose to introduce `{-# LANGUAGE NaturalLiterals #-}`, so `2` is desugared to `2 :: FromNatural a => a` where `class fromNatural :: FromNatural a where Natural -> a` (use `Num` or better `FromInteger` if `NegativeLiterals` is enabled and literal is in fact negative). Putting that behind the language extension doesn't break old code (which needs `Num a => a`). Side-question: how constant folding works when cross-compiling, when `Int` is of different bit-widths on host and target? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: new Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
I'm in great favour of adding Natural literal into core. It was untrivial and I didn't pursue that back then,
As comment:2 says, it's not trivial in the sense of "only 3 lines of code", but it is trivial (or at least easy) in the sense of "just follow the pattern of `Integer`". I often find myself liking things that are simple and explicable even if they do a bit more duplication than we'd ideally like. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: patch Priority: high | Milestone: 8.2.3 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Changes (by hsyl20): * status: new => patch * differential: => Phab:D4212 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: patch Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Changes (by hsyl20): * milestone: 8.2.3 => 8.6.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: patch Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Comment (by darchon): I would really like this patch to land in 8.6.1 as our Clash Haskell-to- Hardware compiler has to work a lot harder with these unsimplified naturals. I just saw that a 8.6 branch was created on git, hence why I'm posting now. Patch D4212 seems to have gotten the OKs, what still needs to happen to it before it lands in HEAD and can end up in the 8.6 branch? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: patch Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Bodigrim): +1 to have it merged into 8.6.1. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: patch Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Comment (by hsyl20): I've just rebased D4212 on master. It should be ready to land. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: patch Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Alright, given how long this patch has been in limbo I'm willing to merge it. Thanks for the rebase, hsyl20. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:18 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14170: 8.2.1 regression: GHC fails to simplify `natVal`
-------------------------------------+-------------------------------------
Reporter: vagarenko | Owner: Bodigrim
Type: bug | Status: patch
Priority: high | Milestone: 8.6.1
Component: Compiler | Version: 8.2.1
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s): Phab:D4212
Wiki Page: |
-------------------------------------+-------------------------------------
Comment (by Ben Gamari
#14170: 8.2.1 regression: GHC fails to simplify `natVal` -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: Bodigrim Type: bug | Status: closed Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4212 Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: patch => closed * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14170#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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