StgRhsClosure freevar and argument name duplicates

Csaba Hruska csaba.hruska at gmail.com
Tue Nov 6 15:47:35 UTC 2018


Ok, I'll open a ticket.
To reproduce:

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


On Tue, Nov 6, 2018 at 4:39 PM Simon Peyton Jones <simonpj at microsoft.com>
wrote:

> can you open a Trac ticket, and explain how to reproduce it?  Does it
> require a patch, or does -ddump-stg show it?
>
>
>
> thanks
>
>
>
> Simion
>
>
>
> *From:* Csaba Hruska <csaba.hruska at gmail.com>
> *Sent:* 06 November 2018 15:36
> *To:* Simon Peyton Jones <simonpj at microsoft.com>
> *Cc:* ghc-devs at haskell.org
> *Subject:* Re: StgRhsClosure freevar and argument name duplicates
>
>
>
> You can reproduce the error with the GHC HEAD and with the attached patch
> for StgLinter.
>
> The patch adds scope checking for the linter.
>
> I've also attached the linter's error output against GHC HEAD.
>
> Compile GHC HEAD with the following settings:
>
> GhcStage1HcOpts=
> GhcStage2HcOpts=-O2 -haddock -dstg-lint
> GhcStage3HcOpts=-O2 -haddock -dstg-lint
>
>
>
> Regards,
>
> Csaba
>
>
>
>
>
> On Tue, Nov 6, 2018 at 12:19 PM Csaba Hruska <csaba.hruska at gmail.com>
> wrote:
>
> Correction: I've also noticed that there are two Main.main top-level
> binders in the generated STG with different uniques.
>
>
>
> On Tue, Nov 6, 2018 at 12:19 PM Csaba Hruska <csaba.hruska at gmail.com>
> wrote:
>
> I've also noticed that there are two Main.main top-level binders in the
> generated STG with different uniques?
>
> And GHC produces a working executable.
>
> Is Main.main an exception or does top-level names have some kind of
> "should be exported" property?
>
>
>
> On Tue, Nov 6, 2018 at 12:02 PM Simon Peyton Jones <simonpj at microsoft.com>
> wrote:
>
> I think top level names should be unique in occ-names; because those
> occ-names generate the symbols in the binary.
>
>
>
> Simon
>
>
>
> *From:* Csaba Hruska <csaba.hruska at gmail.com>
> *Sent:* 06 November 2018 11:01
> *To:* Simon Peyton Jones <simonpj at microsoft.com>
> *Cc:* ghc-devs at haskell.org
> *Subject:* Re: StgRhsClosure freevar and argument name duplicates
>
>
>
> My plan is to extend GHC's STG linter to check the following properties:
>
>    - uniqueness of free var and arg list of StgRhsClosure
>    - top level binding name uniqueness
>
> I'll patch my local GHC 8.2.2 and GHC HEAD. I'll also attach the patch to
> the ticket.
>
> I have a question regarding top level names.
>
> Should the top-level names be unique as occ names or just in unique values?
>
> If not, then what is the rule?
>
>
>
> Thanks,
>
> Csaba
>
>
>
> On Tue, Nov 6, 2018 at 11:13 AM Simon Peyton Jones <simonpj at microsoft.com>
> wrote:
>
> Does this happen in HEAD with GHC’s own STG printer?  If so, could you
> file a Trac ticket – it’s clearly wrong.
>
>
>
> But I do wonder if it could perhaps be something to do with your branch?
>
>
>
> Thanks
>
>
>
> Simon
>
>
>
> *From:* Csaba Hruska <csaba.hruska at gmail.com>
> *Sent:* 05 November 2018 16:33
> *To:* Simon Peyton Jones <simonpj at microsoft.com>
> *Cc:* ghc-devs at haskell.org
> *Subject:* Re: StgRhsClosure freevar and argument name duplicates
>
>
>
> Correction!
>
> The problem happens in integer-gmp:
>
> https://github.com/ghc/ghc/blob/master/libraries/integer-gmp/src/GHC/Integer/Type.hs#L761-L770
> <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc%2Fghc%2Fblob%2Fmaster%2Flibraries%2Finteger-gmp%2Fsrc%2FGHC%2FInteger%2FType.hs%23L761-L770&data=02%7C01%7Csimonpj%40microsoft.com%7C8ed5614402be4321be6908d643fda441%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636771154034475485&sdata=tglY4lglir%2FKqm3ApXo9gW4gHCWeRIBjP7UMEytNjxQ%3D&reserved=0>
>
>
>
> On Mon, Nov 5, 2018 at 5:27 PM Csaba Hruska <csaba.hruska at gmail.com>
> wrote:
>
> An example for the duplication please check the divModInteger
> <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc%2Fghc%2Fblob%2Fmaster%2Flibraries%2Finteger-simple%2FGHC%2FInteger%2FType.hs%23L373-L380&data=02%7C01%7Csimonpj%40microsoft.com%7C8ed5614402be4321be6908d643fda441%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636771154034485494&sdata=6u7J6besY3OM9zfcr0x0LRuo7zJRphr6iHOq6xwO7mo%3D&reserved=0>
> function from integer-simple GHC.Integer.Type.
>
> The STG (GHC 8.2.2) generated from *divModInteger* *::** Integer ->
> Integer -> (# Integer, Integer #) *contains duplications in a closure
> binder list.
>
>
>
> Using my custom STG printer it looks like:
>
> module GHC.Integer.Type where
>
>
>
> using GHC.Prim
> using GHC.Tuple
> using GHC.Types
>
>
>
> GHC.Integer.Type.divModInteger {-083-} =
>   closure (F:) (B:
>   n.s84123 {-s84123-}
>   d.s84124 {-s84124-}) {
>   case GHC.Integer.Type.quotRemInteger {-084-}
>          n.s84123 {-s84123-}
>          d.s84124 {-s84124-}
>   of qr.s84125 {-s84125-} {
>     GHC.Prim.(#,#) {-86-} ipv.s84126 {-s84126-} ipv1.s84127 {-s84127-} ->
>       let $j.s84128 {-s84128-} =
>             closure (F:
>             d.s84124 {-s84124-}
> *            ipv.s84126 {-s84126-}*
> *            ipv1.s84127 {-s84127-}*
> *            ipv.s84126 {-s84126-}*
>             *ipv1.s84127 {-s84127-}*) (B:
>             wild.s84129 {-s84129-}) {
>             let $j1.s84130 {-s84130-} =
>                   closure (F:
>                   d.s84124 {-s84124-}
>                   ipv.s84126 {-s84126-}
>                   ipv1.s84127 {-s84127-}
>                   ipv.s84126 {-s84126-}
>                   ipv1.s84127 {-s84127-}
>                   wild.s84129 {-s84129-}) (B:
>                   wild1.s84131 {-s84131-}) {
>                   case _stg_prim_negateInt#
>                          wild.s84129 {-s84129-}
>                   of sat.s84132 {-s84132-} {
>                     DEFAULT ->
>                       case _stg_prim_==#
>                              wild1.s84131 {-s84131-}
>                              sat.s84132 {-s84132-}
>                       of sat.s84133 {-s84133-} {
>                         DEFAULT ->
>                           case _stg_prim_tagToEnum#
>                                  sat.s84133 {-s84133-}
>                           of wild2.s84134 {-s84134-} {
>                             GHC.Types.False {-612-} ->
>                               GHC.Prim.(#,#) {-86-}
>                                 ipv.s84126 {-s84126-}
>                                 ipv1.s84127 {-s84127-}
>                             GHC.Types.True {-645-} ->
>                               case GHC.Integer.Type.plusInteger {-066-}
>                                      ipv1.s84127 {-s84127-}
>                                      d.s84124 {-s84124-}
>                               of r'.s84135 {-s84135-} {
>                                 DEFAULT ->
>                                   case GHC.Integer.Type.plusInteger {-066-}
>                                          ipv.s84126 {-s84126-}
>                                          GHC.Integer.Type.lvl11 {-r50574-}
>                                   of q'.s84136 {-s84136-} {
>                                     DEFAULT ->
>                                       GHC.Prim.(#,#) {-86-}
>                                         q'.s84136 {-s84136-}
>                                         r'.s84135 {-s84135-}
>                                   }
>                               }
>                           }
>                       }
>                   }}
>
>             in case ipv1.s84127 {-s84127-}
>                of wild1.s84137 {-s84137-} {
>                  GHC.Integer.Type.S# {-621-} i#.s84138 {-s84138-} ->
>                    case _stg_prim_<#
>                           i#.s84138 {-s84138-} 0#
>                    of sat.s84140 {-s84140-} {
>                      DEFAULT ->
>                        case _stg_prim_>#
>                               i#.s84138 {-s84138-} 0#
>                        of sat.s84139 {-s84139-} {
>                          DEFAULT ->
>                            case _stg_prim_-#
>                                   sat.s84139 {-s84139-}
>                                   sat.s84140 {-s84140-}
>                            of sat.s84141 {-s84141-} {
>                              DEFAULT ->
>                                $j1.s84130 {-s84130-}
>                                  sat.s84141 {-s84141-}
>                            }
>                        }
>                    }
>                  GHC.Integer.Type.Jp#
> <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2FGHC.Integer.Type.Jp%23&data=02%7C01%7Csimonpj%40microsoft.com%7C8ed5614402be4321be6908d643fda441%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636771154034495502&sdata=2WLaJGm7NgH0FvibSDarfwBraI9nn0uAZVUH6CwaMno%3D&reserved=0>
> {-r5813-} dt.s84142 {-s84142-} ->
>                    $j1.s84130 {-s84130-} 1#
>                  GHC.Integer.Type.Jn# {-r5814-} dt.s84143 {-s84143-} ->
>                    $j1.s84130 {-s84130-} -1#
>                }}
>
>       in case d.s84124 {-s84124-}
>          of wild.s84144 {-s84144-} {
>            GHC.Integer.Type.S# {-621-} i#.s84145 {-s84145-} ->
>              case _stg_prim_<#
>                     i#.s84145 {-s84145-} 0#
>              of sat.s84147 {-s84147-} {
>                DEFAULT ->
>                  case _stg_prim_>#
>                         i#.s84145 {-s84145-} 0#
>                  of sat.s84146 {-s84146-} {
>                    DEFAULT ->
>                      case _stg_prim_-#
>                             sat.s84146 {-s84146-}
>                             sat.s84147 {-s84147-}
>                      of sat.s84148 {-s84148-} {
>                        DEFAULT ->
>                          $j.s84128 {-s84128-}
>                            sat.s84148 {-s84148-}
>                      }
>                  }
>              }
>            GHC.Integer.Type.Jp#
> <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2FGHC.Integer.Type.Jp%23&data=02%7C01%7Csimonpj%40microsoft.com%7C8ed5614402be4321be6908d643fda441%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636771154034495502&sdata=2WLaJGm7NgH0FvibSDarfwBraI9nn0uAZVUH6CwaMno%3D&reserved=0>
> {-r5813-} dt.s84149 {-s84149-} ->
>              $j.s84128 {-s84128-} 1#
>            GHC.Integer.Type.Jn# {-r5814-} dt.s84150 {-s84150-} ->
>              $j.s84128 {-s84128-} -1#
>          }
>   }}
>
>
>
> On Mon, Nov 5, 2018 at 2:08 PM Simon Peyton Jones <simonpj at microsoft.com>
> wrote:
>
> I don’t think there should be duplicates in either. Do you have a test
> case that shows duplicates?
>
>
>
> Simon
>
>
>
> *From:* ghc-devs <ghc-devs-bounces at haskell.org> *On Behalf Of *Csaba
> Hruska
> *Sent:* 04 November 2018 11:22
> *To:* ghc-devs at haskell.org
> *Subject:* Re: StgRhsClosure freevar and argument name duplicates
>
>
>
> Is it possible that GHC generates STG with invalid binding semantics for
> certain cases that the Cmm codegen fix or ignore?
>
> This could explain my observations.
>
> I've checked the Stg linter source (StgLint.hs ; GHC 8.2.2 and github
> master) and it does not check StgRhsClosure free var and binder list at all.
>
> And the scope checker function (addInScopeVars) does not check for
> duplicates.
>
>
>
> Any thoughts?
>
>
>
> Cheers,
>
> Csaba
>
>
>
> On Sat, Nov 3, 2018 at 9:53 AM Csaba Hruska <csaba.hruska at gmail.com>
> wrote:
>
> Hi,
>
>
>
> Can StgRhsClosure's freevar list ([occ]) or argument list ([bndr]) contain
> duplicates?
>
>
>
> Cheers,
>
> Csaba
>
>
>
> data GenStgRhs bndr occ
>   = StgRhsClosure
>         CostCentreStack         -- CCS to be attached (default is
> CurrentCCS)
>         StgBinderInfo           -- Info about how this binder is used (see
> below)
>         *[occ]*                   -- non-global free vars; a list, rather
> than
>                                 -- a set, because order is important
>         !UpdateFlag             -- ReEntrant | Updatable | SingleEntry
>         *[bndr]*                  -- arguments; if empty, then not a
> function;
>                                 -- as above, order is important.
>         (GenStgExpr bndr occ)   -- body
>
>
>
>
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