Re: StgRhsClosure freevar and argument name duplicates

6 Nov 2018

      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 
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 
*Sent:* 05 November 2018 16:33
*To:* Simon Peyton Jones 
*Cc:* ghc-devs@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...
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%7C0a8467d53f9145e88f9208d6433c6e0e%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636770324161848413&sdata=SQrzwfSloPvCTaEAUd4M3PVHanfjX37xjdRE6BXn2Pc%3D&reserved=0
On Mon, Nov 5, 2018 at 5:27 PM Csaba Hruska 
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%7C0a8467d53f9145e88f9208d6433c6e0e%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636770324161858421&sdata=Tqq7MeFA91LqKwitneuRxoDVwO8EAhWBY%2FN5RmdA4Bg%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#
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{-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#
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{-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 
wrote:
I don’t think there should be duplicates in either. Do you have a test
case that shows duplicates?
Simon
*From:* ghc-devs  *On Behalf Of *Csaba
Hruska
*Sent:* 04 November 2018 11:22
*To:* ghc-devs@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 
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