Two days old build breakage on i386.

[Karel Gardas]

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