[GHC] #15747: GHC panics when builds for arm as: ghc-stage1: panic! (the 'impossible' happened): padLiveArgs -- i > regNum ??

[GHC]

#15747: GHC panics when builds for arm as: ghc-stage1: panic! (the 'impossible'
happened): padLiveArgs -- i > regNum ??
-------------------------------------+-------------------------------------
           Reporter:  slyfox         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 ghc-HEAD fails build as:
 {{{
 $ LANG=C make
 ===--- building phase 0
 make --no-print-directory -f ghc.mk phase=0 phase_0_builds
 make[1]: Nothing to be done for 'phase_0_builds'.
 ===--- building phase 1
 make --no-print-directory -f ghc.mk phase=1 phase_1_builds
 make[1]: Nothing to be done for 'phase_1_builds'.
 ===--- building final phase
 make --no-print-directory -f ghc.mk phase=final all
 "inplace/bin/ghc-stage1" -static  -H32m -O -O0   -Wall   -Iincludes
 -Iincludes/dist -Iincludes/dist-derivedconstants/header -Iincludes/dist-
 ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS
 -DFS_NAMESPACE=rts -this-unit-id rts -dcmm-lint      -i -irts
 -irts/dist/build -Irts/dist/build -irts/dist/build/./autogen
 -Irts/dist/build/./autogen            -O2 -Wcpp-undef    -Wnoncanonical-
 monad-instances  -c rts/HeapStackCheck.cmm -o
 rts/dist/build/HeapStackCheck.o
 You are using an unsupported version of LLVM!
 Currently only 6.0 is supported.
 We will try though...
 ghc-stage1: panic! (the 'impossible' happened)
   (GHC version 8.7.20181014 for arm-unknown-linux):
         padLiveArgs -- i > regNum ??(2,1)
 CallStack (from HasCallStack):
   error, called at compiler/llvmGen/LlvmCodeGen/Base.hs:194:27 in
 ghc:LlvmCodeGen.Base

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

 make[1]: *** [rts/ghc.mk:318: rts/dist/build/HeapStackCheck.o] Error 1
 make: *** [Makefile:127: all] Error 2
 }}}

 The suspect is: https://phabricator.haskell.org/D5190

 GHC is built for '''armv7a-unknown-linux-gnueabihf''' target.

 {{{
 inplace/bin/ghc-stage1 --info
  [("Project name","The Glorious Glasgow Haskell Compilation System")
  ,("GCC extra via C opts"," -fwrapv -fno-builtin")
  ,("C compiler command","armv7a-unknown-linux-gnueabihf-gcc")
  ,("C compiler flags"," -marm -fno-stack-protector")
  ,("C compiler link flags","  -Wl,-z,noexecstack")
  ,("C compiler supports -no-pie","YES")
  ,("Haskell CPP command","armv7a-unknown-linux-gnueabihf-gcc")
  ,("Haskell CPP flags","-E -undef -traditional")
  ,("ld command","armv7a-unknown-linux-gnueabihf-ld.gold")
  ,("ld flags"," -z noexecstack")
  ,("ld supports compact unwind","YES")
  ,("ld supports build-id","YES")
  ,("ld supports filelist","NO")
  ,("ld is GNU ld","YES")
  ,("ar command","armv7a-unknown-linux-gnueabihf-ar")
  ,("ar flags","q")
  ,("ar supports at file","YES")
  ,("ranlib command","armv7a-unknown-linux-gnueabihf-ranlib")
  ,("touch command","touch")
  ,("dllwrap command","armv7a-unknown-linux-gnueabihf-dllwrap")
  ,("windres command","armv7a-unknown-linux-gnueabihf-windres")
  ,("libtool command","libtool")
  ,("perl command","/usr/bin/perl")
  ,("cross compiling","YES")
  ,("target os","OSLinux")
  ,("target arch","ArchARM {armISA = ARMv7, armISAExt = [VFPv3,NEON],
 armABI = HARD}")
  ,("target word size","4")
  ,("target has GNU nonexec stack","True")
  ,("target has .ident directive","True")
  ,("target has subsections via symbols","False")
  ,("target has RTS linker","YES")
  ,("Unregisterised","NO")
  ,("LLVM llc command","llc")
  ,("LLVM opt command","opt")
  ,("LLVM clang command","clang")
  ,("Project version","8.7.20181014")
  ,("Project Git commit id","4a79ae580698ec635a6edd2b56958af2682511dd")
  ,("Booter version","8.4.2")
  ,("Stage","1")
  ,("Build platform","x86_64-unknown-linux")
  ,("Host platform","x86_64-unknown-linux")
  ,("Target platform","arm-unknown-linux")
  ,("Have interpreter","YES")
  ,("Object splitting supported","NO")
  ,("Have native code generator","NO")
  ,("Support SMP","YES")
  ,("Tables next to code","YES")
  ,("RTS ways","l debug thr thr_debug thr_l  dyn debug_dyn thr_dyn
 thr_debug_dyn l_dyn thr_l_dyn ")
  ,("RTS expects libdw","NO")
  ,("Support dynamic-too","YES")
  ,("Support parallel --make","YES")
  ,("Support reexported-modules","YES")
  ,("Support thinning and renaming package flags","YES")
  ,("Support Backpack","YES")
  ,("Requires unified installed package IDs","YES")
  ,("Uses package keys","YES")
  ,("Uses unit IDs","YES")
  ,("Dynamic by default","NO")
  ,("GHC Dynamic","NO")
  ,("GHC Profiled","NO")
  ,("Leading underscore","NO")
  ,("Debug on","False")
  ,("LibDir","/tmp/portage/cross-armv7a-unknown-linux-
 gnueabihf/ghc-9999/work/ghc-9999/inplace/lib")
  ,("Global Package DB","/tmp/portage/cross-armv7a-unknown-linux-
 gnueabihf/ghc-9999/work/ghc-9999/inplace/lib/package.conf.d")
  ]
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15747>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler