On the ghc-7.10 branch, PPC.Regs has duplicate exports (see below). The offending lines are

        fReg,

        sp, r3, r4, r27, r28, r30,

        r0, sp, r3, r4, r27, r28, r30,

        tmpReg,

and indeed there are duplicates.  Why?

git branch -v

* ghc-7.10     e22d7dc nativeGen PPC: fix > 16 bit offsets in stack handling

  master       f17992a [behind 1397] Updaete perf numbers for 32-bit machines

  wip/T10527   eb66575 Use lazy substitution in simplCast

  wip/T10527-2 9e4908b Add an ambient Id substitution to Subst

Simon

compiler/nativeGen/PPC/Regs.hs:41:13: Warning:

    ‘sp’ is exported by ‘sp’ and ‘sp’

compiler/nativeGen/PPC/Regs.hs:41:17: Warning:

    ‘r3’ is exported by ‘r3’ and ‘r3’

compiler/nativeGen/PPC/Regs.hs:41:21: Warning:

    ‘r4’ is exported by ‘r4’ and ‘r4’