PUBLIC PUBLIC Thanks for looking into this! `Paths_ghc_lib` is referenced just because I am using GHC via ghc-lib. You can of course instead use a local full build of GHC for the libDir. Please find an updated version attached that does that – you’ll just have to adapt the definition of `libDir` to your environment. As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊 From: Simon Peyton Jones Sent: Saturday, October 16, 2021 12:52 AM To: Erdi, Gergo ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) I could not compile Main.hs: ~/code/HEAD-1/inplace/bin/ghc-stage1 -c Gergo.hs -package ghc Gergo.hs:4:1: error: Could not find module ‘Paths_ghc_lib’ Use -v (or `:set -v` in ghci) to see a list of the files searched for. | 4 | import qualified Paths_ghc_lib as GHC | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ simonpj@MSRC-3645512:~/tmp$ Would you like to open a ticket rather than do this by email? Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.commailto:simonpj@microsoft.com.) From: Erdi, Gergo mailto:Gergo.Erdi@sc.com> Sent: 15 October 2021 05:35 To: Simon Peyton Jones mailto:simonpj@microsoft.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) PUBLIC PUBLIC OK I now have a standalone demonstrator that shows, at least, that the default method implementation is not specialized. With the attached input programs, the resulting Core (using GHC e46edfcf47d674731935b2ea1443cc7927e071fb) is as follows (only showing the relevant parts): seq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b seq = \ (@(m :: * -> *)) (v_srS [Occ=Once1!] :: Monad m) -> case v_srS of { C:Monad _ [Occ=Dead] v_srV [Occ=Once1] -> v_srV } $dmseq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b $dmseq = \ (@(m :: * -> *)) ($dMonad [Occ=Once1] :: Monad m) (@a) (@b) (ma [Occ=Once1] :: m a) (mb [Occ=OnceL1] :: m b) -> let { sat_ss0 [Occ=Once1] :: a -> m b [LclId] sat_ss0 = \ _ [Occ=Dead] -> mb } in bind @m $dMonad @a @b ma sat_ss0 $fMonadIO :: Monad IO $fMonadIO = C:Monad @IO bindIO $fMonadIO_$cseq; $fMonadIO_$cseq :: forall a b. IO a -> IO b -> IO b $fMonadIO_$cseq = \ (@a) (@b) -> $dmseq @IO $fMonadIO @a @b; foo :: IO () foo = seq @IO $fMonadIO @() @() ioA ioA If I turn on Opt_D_dump_spec, I can see that specializer *is* running, it just doesn’t *do* anything. This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. 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PUBLIC PUBLIC Do you have a full GHC build there? Are you using Hadrian? Did you set `libDir`’s definition in the source file to where you have GHC built? I just tried, and if I remove the files from my GHC build, I am able to rebuild them: mi@localhost[ghc] $ for i in settings llvm-passes llvm-targets; do rm ~/prog/ghc/_build/stage1/lib/$i; done mi@localhost[ghc] $ for i in settings llvm-passes llvm-targets; do ./hadrian/build-stack _build/stage1/lib/$i; done | Successfully generated _build/stage1/lib/settings. Build completed in 0.41s | Copy file: llvm-passes => _build/stage1/lib/llvm-passes Build completed in 0.40s | Copy file: llvm-targets => _build/stage1/lib/llvm-targets Build completed in 0.52s From: Simon Peyton Jones Sent: Tuesday, October 19, 2021 3:54 PM To: Erdi, Gergo ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊 Plenty of tickets turn out to be non-bugs. But they are still searchable, and form a permanent record that may help others, perhaps in unexpected ways. So I encourage you to do so. I successfully compiled the attached Main.hs with HEAD, passing ‘-package ghc’ as a command line argument. When I run it I get simonpj@MSRC-3645512:~/tmp$ ./gergo Missing file: /home/simonpj/code/HEAD-1/compiler/stage1/build/settings So now I’m stuck again. Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.commailto:simonpj@microsoft.com.) From: Erdi, Gergo mailto:Gergo.Erdi@sc.com> Sent: 19 October 2021 02:57 To: Simon Peyton Jones mailto:simonpj@microsoft.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) PUBLIC PUBLIC Thanks for looking into this! `Paths_ghc_lib` is referenced just because I am using GHC via ghc-lib. You can of course instead use a local full build of GHC for the libDir. Please find an updated version attached that does that – you’ll just have to adapt the definition of `libDir` to your environment. As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊 From: Simon Peyton Jones mailto:simonpj@microsoft.com> Sent: Saturday, October 16, 2021 12:52 AM To: Erdi, Gergo mailto:Gergo.Erdi@sc.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) I could not compile Main.hs: ~/code/HEAD-1/inplace/bin/ghc-stage1 -c Gergo.hs -package ghc Gergo.hs:4:1: error: Could not find module ‘Paths_ghc_lib’ Use -v (or `:set -v` in ghci) to see a list of the files searched for. | 4 | import qualified Paths_ghc_lib as GHC | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ simonpj@MSRC-3645512:~/tmp$ Would you like to open a ticket rather than do this by email? Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.commailto:simonpj@microsoft.com.) From: Erdi, Gergo mailto:Gergo.Erdi@sc.com> Sent: 15 October 2021 05:35 To: Simon Peyton Jones mailto:simonpj@microsoft.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) PUBLIC PUBLIC OK I now have a standalone demonstrator that shows, at least, that the default method implementation is not specialized. With the attached input programs, the resulting Core (using GHC e46edfcf47d674731935b2ea1443cc7927e071fb) is as follows (only showing the relevant parts): seq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b seq = \ (@(m :: * -> *)) (v_srS [Occ=Once1!] :: Monad m) -> case v_srS of { C:Monad _ [Occ=Dead] v_srV [Occ=Once1] -> v_srV } $dmseq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b $dmseq = \ (@(m :: * -> *)) ($dMonad [Occ=Once1] :: Monad m) (@a) (@b) (ma [Occ=Once1] :: m a) (mb [Occ=OnceL1] :: m b) -> let { sat_ss0 [Occ=Once1] :: a -> m b [LclId] sat_ss0 = \ _ [Occ=Dead] -> mb } in bind @m $dMonad @a @b ma sat_ss0 $fMonadIO :: Monad IO $fMonadIO = C:Monad @IO bindIO $fMonadIO_$cseq; $fMonadIO_$cseq :: forall a b. IO a -> IO b -> IO b $fMonadIO_$cseq = \ (@a) (@b) -> $dmseq @IO $fMonadIO @a @b; foo :: IO () foo = seq @IO $fMonadIO @() @() ioA ioA If I turn on Opt_D_dump_spec, I can see that specializer *is* running, it just doesn’t *do* anything. This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at https: //www.sc.com/en/our-locations Where you have a Financial Markets relationship with Standard Chartered PLC, Standard Chartered Bank and their subsidiaries (the "Group"), information on the regulatory standards we adhere to and how it may affect you can be found in our Regulatory Compliance Statement at https: //www.sc.com/rcs/ and Regulatory Compliance Disclosures at http: //www.sc.com/rcs/fm Insofar as this communication is not sent by the Global Research team and contains any market commentary, the market commentary has been prepared by the sales and/or trading desk of Standard Chartered Bank or its affiliate. It is not and does not constitute research material, independent research, recommendation or financial advice. Any market commentary is for information purpose only and shall not be relied on for any other purpose and is subject to the relevant disclaimers available at https: //www.sc.com/en/regulatory-disclosures/#market-disclaimer. Insofar as this communication is sent by the Global Research team and contains any research materials prepared by members of the team, the research material is for information purpose only and shall not be relied on for any other purpose, and is subject to the relevant disclaimers available at https: //research.sc.com/research/api/application/static/terms-and-conditions. Insofar as this e-mail contains the term sheet for a proposed transaction, by responding affirmatively to this e-mail, you agree that you have understood the terms and conditions in the attached term sheet and evaluated the merits and risks of the transaction. We may at times also request you to sign the term sheet to acknowledge the same. Please visit https: //www.sc.com/en/regulatory-disclosures/dodd-frank/ for important information with respect to derivative products. This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at https: //www.sc.com/en/our-locations Where you have a Financial Markets relationship with Standard Chartered PLC, Standard Chartered Bank and their subsidiaries (the "Group"), information on the regulatory standards we adhere to and how it may affect you can be found in our Regulatory Compliance Statement at https: //www.sc.com/rcs/ and Regulatory Compliance Disclosures at http: //www.sc.com/rcs/fm Insofar as this communication is not sent by the Global Research team and contains any market commentary, the market commentary has been prepared by the sales and/or trading desk of Standard Chartered Bank or its affiliate. It is not and does not constitute research material, independent research, recommendation or financial advice. Any market commentary is for information purpose only and shall not be relied on for any other purpose and is subject to the relevant disclaimers available at https: //www.sc.com/en/regulatory-disclosures/#market-disclaimer. Insofar as this communication is sent by the Global Research team and contains any research materials prepared by members of the team, the research material is for information purpose only and shall not be relied on for any other purpose, and is subject to the relevant disclaimers available at https: //research.sc.com/research/api/application/static/terms-and-conditions. Insofar as this e-mail contains the term sheet for a proposed transaction, by responding affirmatively to this e-mail, you agree that you have understood the terms and conditions in the attached term sheet and evaluated the merits and risks of the transaction. We may at times also request you to sign the term sheet to acknowledge the same. Please visit https: //www.sc.com/en/regulatory-disclosures/dodd-frank/ for important information with respect to derivative products.

PUBLIC PUBLIC “settings”? Honestly, I have no idea. GHC looks at these files in the directory passed to runGhc, and in my local setup I have some convoluted ghc-lib-based system to persist these files and also the base package.db into a Stack/cabal-installable package, but these are only needed for environments where there’s no bona-fide GHC build directory. I am sure even without Hadrian, you should have these files somewhere under your build directory, since otherwise the same same runGhc function (used inside the GHC executable as well…) wouldn’t work. Maybe someone else with non-Hadrian knowledge can tell you where these files are put in the non-Hadrian build. From: Simon Peyton Jones Sent: Tuesday, October 19, 2021 4:08 PM To: Erdi, Gergo ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) Yes I have a full build. No it was not built with Hadrian. I did not realise that your system relied not only on GHC as a library, but also on the build system that you use to build GHC. I guess I can try that, but probably not today. But what is “settings”? Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.commailto:simonpj@microsoft.com.) From: Erdi, Gergo mailto:Gergo.Erdi@sc.com> Sent: 19 October 2021 09:03 To: Simon Peyton Jones mailto:simonpj@microsoft.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) PUBLIC PUBLIC Do you have a full GHC build there? Are you using Hadrian? Did you set `libDir`’s definition in the source file to where you have GHC built? I just tried, and if I remove the files from my GHC build, I am able to rebuild them: mi@localhost[ghc] $ for i in settings llvm-passes llvm-targets; do rm ~/prog/ghc/_build/stage1/lib/$i; done mi@localhost[ghc] $ for i in settings llvm-passes llvm-targets; do ./hadrian/build-stack _build/stage1/lib/$i; done | Successfully generated _build/stage1/lib/settings. Build completed in 0.41s | Copy file: llvm-passes => _build/stage1/lib/llvm-passes Build completed in 0.40s | Copy file: llvm-targets => _build/stage1/lib/llvm-targets Build completed in 0.52s From: Simon Peyton Jones mailto:simonpj@microsoft.com> Sent: Tuesday, October 19, 2021 3:54 PM To: Erdi, Gergo mailto:Gergo.Erdi@sc.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊 Plenty of tickets turn out to be non-bugs. But they are still searchable, and form a permanent record that may help others, perhaps in unexpected ways. So I encourage you to do so. I successfully compiled the attached Main.hs with HEAD, passing ‘-package ghc’ as a command line argument. When I run it I get simonpj@MSRC-3645512:~/tmp$ ./gergo Missing file: /home/simonpj/code/HEAD-1/compiler/stage1/build/settings So now I’m stuck again. Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.commailto:simonpj@microsoft.com.) From: Erdi, Gergo mailto:Gergo.Erdi@sc.com> Sent: 19 October 2021 02:57 To: Simon Peyton Jones mailto:simonpj@microsoft.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) PUBLIC PUBLIC Thanks for looking into this! `Paths_ghc_lib` is referenced just because I am using GHC via ghc-lib. You can of course instead use a local full build of GHC for the libDir. Please find an updated version attached that does that – you’ll just have to adapt the definition of `libDir` to your environment. As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊 From: Simon Peyton Jones mailto:simonpj@microsoft.com> Sent: Saturday, October 16, 2021 12:52 AM To: Erdi, Gergo mailto:Gergo.Erdi@sc.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) I could not compile Main.hs: ~/code/HEAD-1/inplace/bin/ghc-stage1 -c Gergo.hs -package ghc Gergo.hs:4:1: error: Could not find module ‘Paths_ghc_lib’ Use -v (or `:set -v` in ghci) to see a list of the files searched for. | 4 | import qualified Paths_ghc_lib as GHC | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ simonpj@MSRC-3645512:~/tmp$ Would you like to open a ticket rather than do this by email? Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.commailto:simonpj@microsoft.com.) From: Erdi, Gergo mailto:Gergo.Erdi@sc.com> Sent: 15 October 2021 05:35 To: Simon Peyton Jones mailto:simonpj@microsoft.com>; 'Matthew Pickering' mailto:matthewtpickering@gmail.com> Cc: Montelatici, Raphael Laurent mailto:Raphael.Montelatici@sc.com>; 'GHC' mailto:ghc-devs@haskell.org> Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*) PUBLIC PUBLIC OK I now have a standalone demonstrator that shows, at least, that the default method implementation is not specialized. With the attached input programs, the resulting Core (using GHC e46edfcf47d674731935b2ea1443cc7927e071fb) is as follows (only showing the relevant parts): seq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b seq = \ (@(m :: * -> *)) (v_srS [Occ=Once1!] :: Monad m) -> case v_srS of { C:Monad _ [Occ=Dead] v_srV [Occ=Once1] -> v_srV } $dmseq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b $dmseq = \ (@(m :: * -> *)) ($dMonad [Occ=Once1] :: Monad m) (@a) (@b) (ma [Occ=Once1] :: m a) (mb [Occ=OnceL1] :: m b) -> let { sat_ss0 [Occ=Once1] :: a -> m b [LclId] sat_ss0 = \ _ [Occ=Dead] -> mb } in bind @m $dMonad @a @b ma sat_ss0 $fMonadIO :: Monad IO $fMonadIO = C:Monad @IO bindIO $fMonadIO_$cseq; $fMonadIO_$cseq :: forall a b. IO a -> IO b -> IO b $fMonadIO_$cseq = \ (@a) (@b) -> $dmseq @IO $fMonadIO @a @b; foo :: IO () foo = seq @IO $fMonadIO @() @() ioA ioA If I turn on Opt_D_dump_spec, I can see that specializer *is* running, it just doesn’t *do* anything. This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at https: //www.sc.com/en/our-locations Where you have a Financial Markets relationship with Standard Chartered PLC, Standard Chartered Bank and their subsidiaries (the "Group"), information on the regulatory standards we adhere to and how it may affect you can be found in our Regulatory Compliance Statement at https: //www.sc.com/rcs/ and Regulatory Compliance Disclosures at http: //www.sc.com/rcs/fm Insofar as this communication is not sent by the Global Research team and contains any market commentary, the market commentary has been prepared by the sales and/or trading desk of Standard Chartered Bank or its affiliate. It is not and does not constitute research material, independent research, recommendation or financial advice. Any market commentary is for information purpose only and shall not be relied on for any other purpose and is subject to the relevant disclaimers available at https: //www.sc.com/en/regulatory-disclosures/#market-disclaimer. Insofar as this communication is sent by the Global Research team and contains any research materials prepared by members of the team, the research material is for information purpose only and shall not be relied on for any other purpose, and is subject to the relevant disclaimers available at https: //research.sc.com/research/api/application/static/terms-and-conditions. Insofar as this e-mail contains the term sheet for a proposed transaction, by responding affirmatively to this e-mail, you agree that you have understood the terms and conditions in the attached term sheet and evaluated the merits and risks of the transaction. We may at times also request you to sign the term sheet to acknowledge the same. Please visit https: //www.sc.com/en/regulatory-disclosures/dodd-frank/ for important information with respect to derivative products. This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at https: //www.sc.com/en/our-locations Where you have a Financial Markets relationship with Standard Chartered PLC, Standard Chartered Bank and their subsidiaries (the "Group"), information on the regulatory standards we adhere to and how it may affect you can be found in our Regulatory Compliance Statement at https: //www.sc.com/rcs/ and Regulatory Compliance Disclosures at http: //www.sc.com/rcs/fm Insofar as this communication is not sent by the Global Research team and contains any market commentary, the market commentary has been prepared by the sales and/or trading desk of Standard Chartered Bank or its affiliate. It is not and does not constitute research material, independent research, recommendation or financial advice. Any market commentary is for information purpose only and shall not be relied on for any other purpose and is subject to the relevant disclaimers available at https: //www.sc.com/en/regulatory-disclosures/#market-disclaimer. Insofar as this communication is sent by the Global Research team and contains any research materials prepared by members of the team, the research material is for information purpose only and shall not be relied on for any other purpose, and is subject to the relevant disclaimers available at https: //research.sc.com/research/api/application/static/terms-and-conditions. Insofar as this e-mail contains the term sheet for a proposed transaction, by responding affirmatively to this e-mail, you agree that you have understood the terms and conditions in the attached term sheet and evaluated the merits and risks of the transaction. We may at times also request you to sign the term sheet to acknowledge the same. Please visit https: //www.sc.com/en/regulatory-disclosures/dodd-frank/ for important information with respect to derivative products. This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at https: //www.sc.com/en/our-locations Where you have a Financial Markets relationship with Standard Chartered PLC, Standard Chartered Bank and their subsidiaries (the "Group"), information on the regulatory standards we adhere to and how it may affect you can be found in our Regulatory Compliance Statement at https: //www.sc.com/rcs/ and Regulatory Compliance Disclosures at http: //www.sc.com/rcs/fm Insofar as this communication is not sent by the Global Research team and contains any market commentary, the market commentary has been prepared by the sales and/or trading desk of Standard Chartered Bank or its affiliate. It is not and does not constitute research material, independent research, recommendation or financial advice. Any market commentary is for information purpose only and shall not be relied on for any other purpose and is subject to the relevant disclaimers available at https: //www.sc.com/en/regulatory-disclosures/#market-disclaimer. Insofar as this communication is sent by the Global Research team and contains any research materials prepared by members of the team, the research material is for information purpose only and shall not be relied on for any other purpose, and is subject to the relevant disclaimers available at https: //research.sc.com/research/api/application/static/terms-and-conditions. Insofar as this e-mail contains the term sheet for a proposed transaction, by responding affirmatively to this e-mail, you agree that you have understood the terms and conditions in the attached term sheet and evaluated the merits and risks of the transaction. We may at times also request you to sign the term sheet to acknowledge the same. 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Hi, If there is a ticket then I can look into it next week. Cheers, Matt On Fri, Oct 22, 2021 at 12:11 PM Simon Peyton Jones wrote:

I’m out of cycles. Do please open a ticket. You are more likely to get attention that way.

Matthew: maybe you can help with reproducing this?

SImon

PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.com.)

From: Erdi, Gergo Sent: 19 October 2021 09:36 To: Simon Peyton Jones ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

PUBLIC

PUBLIC

“settings”? Honestly, I have no idea. GHC looks at these files in the directory passed to runGhc, and in my local setup I have some convoluted ghc-lib-based system to persist these files and also the base package.db into a Stack/cabal-installable package, but these are only needed for environments where there’s no bona-fide GHC build directory.

I am sure even without Hadrian, you should have these files somewhere under your build directory, since otherwise the same same runGhc function (used inside the GHC executable as well…) wouldn’t work. Maybe someone else with non-Hadrian knowledge can tell you where these files are put in the non-Hadrian build.

From: Simon Peyton Jones Sent: Tuesday, October 19, 2021 4:08 PM To: Erdi, Gergo ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

Yes I have a full build. No it was not built with Hadrian. I did not realise that your system relied not only on GHC as a library, but also on the build system that you use to build GHC.

I guess I can try that, but probably not today. But what is “settings”?

Simon

PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.com.)

From: Erdi, Gergo Sent: 19 October 2021 09:03 To: Simon Peyton Jones ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

PUBLIC

PUBLIC

Do you have a full GHC build there? Are you using Hadrian? Did you set `libDir`’s definition in the source file to where you have GHC built? I just tried, and if I remove the files from my GHC build, I am able to rebuild them:

mi@localhost[ghc] $ for i in settings llvm-passes llvm-targets; do rm ~/prog/ghc/_build/stage1/lib/$i; done

mi@localhost[ghc] $ for i in settings llvm-passes llvm-targets; do ./hadrian/build-stack _build/stage1/lib/$i; done

| Successfully generated _build/stage1/lib/settings.

Build completed in 0.41s

| Copy file: llvm-passes => _build/stage1/lib/llvm-passes

Build completed in 0.40s

| Copy file: llvm-targets => _build/stage1/lib/llvm-targets

Build completed in 0.52s

From: Simon Peyton Jones Sent: Tuesday, October 19, 2021 3:54 PM To: Erdi, Gergo ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊

Plenty of tickets turn out to be non-bugs. But they are still searchable, and form a permanent record that may help others, perhaps in unexpected ways. So I encourage you to do so.

I successfully compiled the attached Main.hs with HEAD, passing ‘-package ghc’ as a command line argument.

When I run it I get

simonpj@MSRC-3645512:~/tmp$ ./gergo

Missing file: /home/simonpj/code/HEAD-1/compiler/stage1/build/settings

So now I’m stuck again.

Simon

PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.com.)

From: Erdi, Gergo Sent: 19 October 2021 02:57 To: Simon Peyton Jones ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

PUBLIC

PUBLIC

Thanks for looking into this!

`Paths_ghc_lib` is referenced just because I am using GHC via ghc-lib. You can of course instead use a local full build of GHC for the libDir. Please find an updated version attached that does that – you’ll just have to adapt the definition of `libDir` to your environment.

As for opening a ticket – a big part of the problem is that I don’t even know yet if I’m doing something wrong, or GHC is! So it’s not clear what the ticket would even be for – “I’m using the GHC API wrongly” is not a strong bug report 😊

From: Simon Peyton Jones Sent: Saturday, October 16, 2021 12:52 AM To: Erdi, Gergo ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: [External] RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

I could not compile Main.hs:

~/code/HEAD-1/inplace/bin/ghc-stage1 -c Gergo.hs -package ghc

Gergo.hs:4:1: error:

Could not find module ‘Paths_ghc_lib’

Use -v (or `:set -v` in ghci) to see a list of the files searched for.

|

4 | import qualified Paths_ghc_lib as GHC

| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

simonpj@MSRC-3645512:~/tmp$

Would you like to open a ticket rather than do this by email?

Simon

PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.com.)

From: Erdi, Gergo Sent: 15 October 2021 05:35 To: Simon Peyton Jones ; 'Matthew Pickering' Cc: Montelatici, Raphael Laurent ; 'GHC' Subject: RE: Specialisation doesn't kick in -- NOW WITH MINIMAL WORKING EXAMPLE (RE: Instantiation of overloaded definition *in Core*)

PUBLIC

PUBLIC

OK I now have a standalone demonstrator that shows, at least, that the default method implementation is not specialized. With the attached input programs, the resulting Core (using GHC e46edfcf47d674731935b2ea1443cc7927e071fb) is as follows (only showing the relevant parts):

seq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b

seq

= \ (@(m :: * -> *)) (v_srS [Occ=Once1!] :: Monad m) ->

case v_srS of { C:Monad _ [Occ=Dead] v_srV [Occ=Once1] -> v_srV }

$dmseq :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b

$dmseq

= \ (@(m :: * -> *))

($dMonad [Occ=Once1] :: Monad m)

(@a)

(@b)

(ma [Occ=Once1] :: m a)

(mb [Occ=OnceL1] :: m b) ->

let {

sat_ss0 [Occ=Once1] :: a -> m b

[LclId]

sat_ss0 = \ _ [Occ=Dead] -> mb } in

bind @m $dMonad @a @b ma sat_ss0

$fMonadIO :: Monad IO

$fMonadIO = C:Monad @IO bindIO $fMonadIO_$cseq;

$fMonadIO_$cseq :: forall a b. IO a -> IO b -> IO b

$fMonadIO_$cseq = \ (@a) (@b) -> $dmseq @IO $fMonadIO @a @b;

foo :: IO ()

foo = seq @IO $fMonadIO @() @() ioA ioA

If I turn on Opt_D_dump_spec, I can see that specializer *is* running, it just doesn’t *do* anything.

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