Cannot build ghc HEAD with LLVM ARM due to globalRegMaybe

[Moritz Angermann]

Hi Janek,

yea :) I think it went by unnoticed.  Patch is already in Phab,

https://phabricator.haskell.org/D208

Not sure how to speed up the review process, though ;-)

Cheers,
  Moritz

On Sep 15, 2014, at 11:13 AM, Jan Stolarek <jan.stolarek at p.lodz.pl> wrote:

> I think it is best to fill in a bug report and attach a patch - I'm afraid this mail may have gone 
> unnoticed :-)
> 
> Janek
> 
> Dnia piątek, 12 września 2014, Moritz Angermann napisał:
>> Hi,
>> 
>> when trying to compile a ghc HEAD on LLVM ARM, I end up getting an
>> exception:
>> 
>>    ghc-stage1: panic! (the 'impossible' happened)
>>      (GHC version 7.9.20140911 for arm-apple-ios):
>>        globalRegMaybe
>> 
>> After some digging I found that a new call to globalRegMaybe was introduced
>> here:
>> http://git.haskell.org/ghc.git/blob/HEAD:/compiler/cmm/CmmSink.hs#l231 on
>> 2014-04-29 in commit:
>> http://git.haskell.org/ghc.git/commitdiff/83a003fcaec93dbfd5b46837f2bf33534
>> 12b9877
>> 
>> In a similar timeframe (since 2014-05-02) /include/CodeGen.Platform.hs was
>> changed:
>> http://git.haskell.org/ghc.git/blobdiff/b0534f78a73f972e279eed4447a5687bd6a
>> 8308e..HEAD:/includes/CodeGen.Platform.hs
>> 
>> introducing a set of new ifdef/elif/endif pairs. Especially for
>> MACHREGS_NO_REGS, namely:
>> 
>>    -#endif
>>     globalRegMaybe _                        = Nothing
>>    +#elif MACHREGS_NO_REGS
>>    +globalRegMaybe _ = Nothing
>>    +#else
>>    +globalRegMaybe = panic "globalRegMaybe not defined for this platform"
>>    +#endif
>> 
>> ARM.hs
>> (http://git.haskell.org/ghc.git/blob/23892440032fcab8a6a753916d506857674169
>> ec:/compiler/codeGen/CodeGen/Platform/ARM.hs) however, has:
>> 
>>    #define MACHREGS_NO_REGS 0
>>    #define MACHREGS_arm 1
>> 
>> where MACHREGS_arm 1 has no effect on the subsequently imported
>> CodeGen.Platform.hs.
>> 
>> Therefore I propose that a change to ARM.hs is made to set
>> MACHREGS_NO_REGS to 1.
>> 
>> Cheers,
>> Moritz
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> 
>