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@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