Two days old build breakage on i386.

[Mateusz Kowalczyk]

On 06/26/2014 12:37 PM, Johan Tibell wrote:
> I think it's reasonable to say my change triggers the issue, but I don't
> know why and I need someone who understand the register allocator better
> (e.g. Simon M) to at least give me some pointers on how to debug this. If
> this is causing more trouble than build bot breakages (which is bad
> enough), let me know and I'll either revert temporarily and or try to work
> around the issue.
> 
> Also, how do I repro this if I don't have a x86 machine lying around? Have
> people been successful working on these kind of issues in a VM?
> 

I can give you shell access to the machine in the OP but it's not the
fastest thing in the world (3GHz Core 2 Duo). Let me know if you want it.

> 
> On Thu, Jun 26, 2014 at 10:55 AM, Karel Gardas <karel.gardas at centrum.cz>
> wrote:
> 
>>
>> Hello,
>>
>> builders running on i386 building for this platform caught issue which
>> shows as a build breakage:
>>
>> ghc-stage1: panic! (the 'impossible' happened)
>> (GHC version 7.9.20140624 for i386-unknown-linux):
>> RegAllocLinear.allocRegsAndSpill: no spill candidates
>> allocating vreg: VirtualRegI n1Q6
>> assignment: [(c1PV,InMem 2),(n1Q5,InBoth (RealRegSingle 3) 0),(n1Q6,InMem
>> 1),(n1Q7,InMem 3),(n1Q9,InReg (RealRegSingle 2))]
>> freeRegs: FreeRegs 4282318848
>> initFreeRegs: FreeRegs 4282318861
>> Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
>> make[1]: *** [libraries/ghc-prim/dist-install/build/GHC/PrimopWrappers.o]
>> Error 1
>> libraries/ghc-prim/ghc.mk:4: recipe for target 'libraries/ghc-prim/dist-
>> install/build/GHC/PrimopWrappers.o' failed
>>
>> Have a look for example on linux-i386 buildot log here:
>> http://haskell.inf.elte.hu/builders/validator1-linux-x86-head/18/7.html
>>
>> Anyway, this happens on Linux, FreeBSD and Solaris buildbots on i386 so
>> it's OS independent and probably 32bit/i386 platform specific and it's two
>> days old breakage now. The last two night builds fail on all mentioned
>> buildbots. I'm not sure but perhaps:
>>
>> commit d8abf85f8ca176854e9d5d0b12371c4bc402aac3
>> Author: Johan Tibell <johan.tibell at gmail.com>
>> Date:   Mon Jun 9 11:43:21 2014 +0200
>>
>> triggers that issue? I'm not claiming that the commit is actual culprit,
>> this may be just recently un-hidden issue in linear regs allocator on i386!
>>
>> Thanks!
>> Karel
>>
> 
> 
> 
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-- 
Mateusz K.