Re: StgRhsClosure freevar and argument name duplicates

https://ghc.haskell.org/trac/ghc/ticket/15867 On Tue, Nov 6, 2018 at 4:47 PM Csaba Hruska wrote:

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 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 *Sent:* 06 November 2018 15:36 *To:* Simon Peyton Jones *Cc:* ghc-devs@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 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 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 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 *Sent:* 06 November 2018 11:01 *To:* Simon Peyton Jones *Cc:* ghc-devs@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 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%7C8ed5614402be4321be6908d643fda441%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636771154034475485&sdata=tglY4lglir%2FKqm3ApXo9gW4gHCWeRIBjP7UMEytNjxQ%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%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 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