#7814: panic in PPC NCG --------------------------+------------------------------------------------- Reporter: heisenbug | Owner: heisenbug Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Os: Unknown/Multiple Architecture: powerpc | Failure: Building GHC failed Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | --------------------------+------------------------------------------------- Changes (by igloo): * difficulty: => Unknown Old description:
I get panics in the NCG PPC register allocator while compiling these files:
rts_dist_HC rts/dist/build/StgStdThunks.dyn_o rts_dist_HC rts/dist/build/StgStdThunks.thr_dyn_o rts_dist_HC rts/dist/build/StgStdThunks.l_dyn_o rts_dist_HC rts/dist/build/StgStdThunks.thr_l_dyn_o HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/Classes.o HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/CString.o HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/Debug.o
The panic message is like this: {{{ ghc-stage1: panic! (the 'impossible' happened) (GHC version 7.7.20130405 for powerpc-montavista-linux): allocateRegsAndSpill: Cannot read from uninitialized register %vI_nff
}}}
This makes the bootstapping of PPC cross compiler, ehm, delicate.
There is a comment in compiler/nativeGen/RegAlloc/Linear/Main.hs:756
Nothing | reading -> pprPanic "allocateRegsAndSpill: Cannot read from uninitialized register" (ppr r) -- NOTE: if the input to the NCG contains some -- unreachable blocks with junk code, this panic -- might be triggered. Make sure you only feed -- sensible code into the NCG. In CmmPipeline we -- call removeUnreachableBlocks at the end for this -- reason.
So we have a 'junk code' issue here.
Any hints how I can debug this?
New description: I get panics in the NCG PPC register allocator while compiling these files: {{{ rts_dist_HC rts/dist/build/StgStdThunks.dyn_o rts_dist_HC rts/dist/build/StgStdThunks.thr_dyn_o rts_dist_HC rts/dist/build/StgStdThunks.l_dyn_o rts_dist_HC rts/dist/build/StgStdThunks.thr_l_dyn_o HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/Classes.o HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/CString.o HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/Debug.o }}} The panic message is like this: {{{ ghc-stage1: panic! (the 'impossible' happened) (GHC version 7.7.20130405 for powerpc-montavista-linux): allocateRegsAndSpill: Cannot read from uninitialized register %vI_nff }}} This makes the bootstapping of PPC cross compiler, ehm, delicate. There is a comment in compiler/nativeGen/RegAlloc/Linear/Main.hs:756 {{{ Nothing | reading -> pprPanic "allocateRegsAndSpill: Cannot read from uninitialized register" (ppr r) -- NOTE: if the input to the NCG contains some -- unreachable blocks with junk code, this panic -- might be triggered. Make sure you only feed -- sensible code into the NCG. In CmmPipeline we -- call removeUnreachableBlocks at the end for this -- reason. }}} So we have a 'junk code' issue here. Any hints how I can debug this? -- -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7814#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler