StgRhsClosure freevar and argument name duplicates
Csaba Hruska
csaba.hruska at gmail.com
Tue Nov 6 15:36:22 UTC 2018
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%7Cd47aada6162e4c2da86608d643d720dd%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636770988594092291&sdata=re0I7r77Hli0UuEv07vBNRRrWttdDLGE8BaYYQZNr8o%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%7Cd47aada6162e4c2da86608d643d720dd%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636770988594102189&sdata=sEVZfZHmc9%2BQxzp8bQijgiRBPvGv5U0lsQi9lElUoj8%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%7Cd47aada6162e4c2da86608d643d720dd%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636770988594102189&sdata=KaYvZjgoFE%2BNT%2FbQ4mZlKqB8Q%2FT50CUstmJS3RGtur0%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%7Cd47aada6162e4c2da86608d643d720dd%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636770988594112198&sdata=baugV3HdRfINk51GmbD51LtoW1A3S7p4yKXvIXseEgA%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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