Two days old build breakage on i386.

Simon Peyton Jones simonpj at
Thu Jun 26 12:13:24 UTC 2014

Aaaargh!  Once again the Windows build is broken.  I am utterly stalled.

Moreover -fregs-graph and -fregs-iterative now *silently* do nothing.  At least they should elicit warnings saying that they are disabled pending the fix to X and Y.

Please can someone bisect to find out which patch is the culprit?  

I wish we had a more systematic way to find this out. I hate being the main person who gets stuck because some unrelated change has broken the Windows build.  (Thanks for Karel, who got to it a day before me.)



| -----Original Message-----
| From: ghc-devs [mailto:ghc-devs-bounces at] On Behalf Of Karel
| Gardas
| Sent: 26 June 2014 09:56
| To: ghc-devs; Johan Tibell
| Subject: Two days old build breakage on i386.
| 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:
| make[1]: ***
| [libraries/ghc-prim/dist-install/build/GHC/PrimopWrappers.o] Error 1
| libraries/ghc-prim/ recipe for target
| 'libraries/ghc-prim/dist-install/build/GHC/PrimopWrappers.o' failed
| Have a look for example on linux-i386 buildot log here:
| 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>
| 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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