#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 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 csabahruska): * Attachment "StgScopeCheck.patch" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 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: | -------------------------------------+------------------------------------- Description changed by csabahruska: Old description:

StgRhsClosure can contain duplicated names in its free variable and argument list.

Example bug: libraries/integer-gmp/src/GHC/Integer/Type.hs

GHC HEAD and 8.2.2 has this issue.

I have not checked with other versions.

I've extended the STG linter to do scope checking. See the patch attached.

To reproduce: * patch GHC head: `git apply StgScopeCheck.patch` * make sure every compiled stg is linted: add `-dstg-lint` to GhcStage2HcOpts GhcLibHcOpts GhcRtsHcOpts config vars * compile GHC HEAD

Background info: I've found this issue because I'm using GHC as a Haskell fronted for my whole program compiler project. I work on The GRIN Compiler (https://github.com/grin-tech) where GHC/GRIN compiles STG to GRIN.

New description: StgRhsClosure can contain duplicated names in its free variable and argument list. Example bug: libraries/integer-gmp/src/GHC/Integer/Type.hs GHC HEAD and 8.2.2 has this issue. I have not checked with other versions. I've extended the STG linter to do scope checking. See the patch attached. To reproduce: * patch GHC head: `git apply StgScopeCheck.patch` * make sure every compiled stg is linted: add the following to `mk/build.mk`\\ {{{ GhcStage2HcOpts += -dstg-lint GhcLibHcOpts += -dstg-lint GhcRtsHcOpts += -dstg-lint }}} * compile GHC HEAD Background info: I've found this issue because I'm using GHC as a Haskell fronted for my whole program compiler project. I work on The GRIN Compiler (https://github.com/grin-tech) where GHC/GRIN compiles STG to GRIN. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 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 csabahruska): Maybe my proposed STG scope checker is too strict. It does not allow name shadowing, but I can refine it further.\\ But the code above is definitely a bug as it contains duplicates in the closure binder list. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: | Keywords: CodeGen 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 simonpj): * keywords: => CodeGen -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: sgraf Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: | Keywords: CodeGen 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 sgraf): The `Void# is redefined` errors are related to shadowing. As you pointed out, that's a little too strict. The other errors, due to duplicated occs, are more concerning. This happens after unarisation. This is the offending STG before unarise: {{{ case GHC.Integer.Type.quotRemInteger n_sf5G d_sf5H of qr_sf5I [Occ=Once] { (#,#) ipv_sf5J [Occ=Once] ipv1_sf5K -> let-no-escape { $j3_sf5L [Occ=Once*!T[1], Dmd=] :: GHC.Prim.Int# -> (# GHC.Integer.Type.Integer, GHC.Integer.Type.Integer #) [LclId[JoinId(1)], Arity=1, Str=, Unf=OtherCon []] = sat-only [d_sf5H qr_sf5I ipv_sf5J ipv1_sf5K] \r [wild_sf5M] -> ... }}} Unarise splits the occurrence of `qr_sf5I` into its constituents `ipv_sf5J` and `ipv1_sf5K` without looking for duplicates: {{{ case quotRemInteger n_sf5G d_sf5H of qr_sf5I [Occ=Once] { (#,#) ipv_sf5J [Occ=Once] ipv1_sf5K -> let-no-escape { $j3_sf5L [Occ=Once*!T[1], Dmd=] :: Int# -> (# Integer, Integer #) [LclId[JoinId(1)], Arity=1, Str=, Unf=OtherCon []] = sat-only [d_sf5H ipv_sf5J ipv1_sf5K ipv_sf5J ipv1_sf5K] \r [wild_sf5M] ... }}} Let's see where... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: sgraf Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5310 Wiki Page: | -------------------------------------+------------------------------------- Changes (by csabahruska): * Attachment "StgScopeCheck2.patch" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: sgraf Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5310 Wiki Page: | -------------------------------------+------------------------------------- Comment (by csabahruska): Or do we want to accept this as some kind of name shadowing? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: sgraf Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5310 Wiki Page: | -------------------------------------+------------------------------------- Comment (by sgraf): Hmm. I'm inclined to accept the shadowing, it's like nested lambdas, after all. Also, since free var occurrences never were a problem before (presumably because `StgToCmm` nubs them anyway) and since there are plans in #15754 to get rid of that field altogether, I'm not sure if this really is a sensible thing to lint for. No doubt, the STG is extremely fishy, but if we are going to remove FV occs from `StgRhsClosure` anyway, I don't see great value in fixing these non-severe bugs. Simon is free to overrule me here, in which case I'd be happy to fix this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: sgraf Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: wontfix | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5310 Wiki Page: | -------------------------------------+------------------------------------- Changes (by sgraf): * status: patch => closed * resolution: => wontfix Comment: Great! Have fun and re-open if this doesn't work for you. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15867: STG scope error -------------------------------------+------------------------------------- Reporter: csabahruska | Owner: sgraf Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: wontfix | Keywords: CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5310 Wiki Page: | -------------------------------------+------------------------------------- Changes (by csabahruska): * Attachment "StgScopeCheck3.patch" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15867 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler