bundle panic

[Simon Marlow]

On 16/11/13 00:16, Simon Peyton-Jones wrote:
> I’ve looked into this myself.  I don’t think it’s actually anything
> wrong in gmp-wrappers.  It’s because CmmBuildInfoTables expects all the
> info tables in the (CmmProc info_tbls lbl g) to be defined in the graph g.
>
> But Jan’s new optimisation to the stack overflow check (Note [Always
> false stack check] in CmmLayoutStack) ends up dropping a conditional
> branch, so a call to gc is eliminated, and hence a proc point is
> eliminated, and we end up with an unused thing in info_tbls, which
> confuses CmmBuildInfoTables

> Sigh. I don’t know why this only happens on Windows.  I’m looking into a fix

Perhaps this is a problem that only shows up with proc points, which is 
why you wouldn't see it on x86_64/Linux.  Let me know if you get stuck 
and I'll try to look into it.

FYI eliminating always-false stack checks is not new, it was temporarily 
broken by:

commit 94125c97e49987e91fa54da6c86bc6d17417f5cf
Author: Jan Stolarek <jan.stolarek at p.lodz.pl>
Date:   Wed Oct 16 09:45:56 2013 +0200

     Generate (old + 0) instead of Sp in stack checks

and then fixed up by:

commit 1cf0c8ad321d1d358cbec46d35be02566faf2d00
Author: Jan Stolarek <jan.stolarek at p.lodz.pl>
Date:   Thu Oct 17 23:17:06 2013 +0200

     Optimise stack checks that are always false

Cheers,
Simon


>
>
> Simon
>
> *From:*Simon Peyton-Jones
> *Sent:* 15 November 2013 22:18
> *To:* ghc-devs at haskell.org
> *Subject:* bundle panic
>
> Windows build is failing again in a new way.  It was fine a couple of
> days ago. Does this ring any bells?
>
> ghc-stage1.exe: panic! (the 'impossible' happened)
>
>    (GHC version 7.7.20131107 for i386-unknown-mingw32):
>
>       bundle
>
> Simon
>
> "inplace/bin/ghc-stage1.exe" -static  -H32m -O -Werror -Wall -H64m
> -O0    -package-name integer-gmp-0.5.1.0 -hide-all-packages -i
> -ilibraries/integer-gmp/. -ilibraries/integer-gmp/dist-install/build
> -ilibraries/integer-gmp/dist-install/build/autogen
> -Ilibraries/integer-gmp/dist-install/build
> -Ilibraries/integer-gmp/dist-install/build/autogen
> -Ilibraries/integer-gmp/.    -optP-include
> -optPlibraries/integer-gmp/dist-install/build/autogen/cabal_macros.h
> -package ghc-prim-0.3.1.0 -Wall -package-name integer-gmp -XHaskell2010
> -dcore-lint  -no-user-package-db -rtsopts
> -Ilibraries/integer-gmp/mkGmpDerivedConstants/dist     -c
> libraries/integer-gmp/cbits/gmp-wrappers.cmm -o
> libraries/integer-gmp/dist-install/build/cbits/gmp-wrappers.o
>
> ghc-stage1.exe: panic! (the 'impossible' happened)
>
>    (GHC version 7.7.20131107 for i386-unknown-mingw32):
>
>       bundle
>
>      c8 integer_cmm_importIntegerFromByteArrayzh [(c8,
>
>                                                    label: block{v c8}_info
>
>                                                    rep:StackRep [False,
> True, True, True]),
>
>                                                   (cg,
>
>                                                    label: block{v cg}_info
>
>                                                    rep:StackRep [False,
> True, True, True])]
>
> Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
>
> HEAD (master)$
>
>
>
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