[Power8] Invalid CTR loop in sorting.jl test

[vchuravy]

Reduced with bugpoint to:

[vchuravy@service0001 ctr]$ cat bugpoint-reduced-simplified.ll
; ModuleID = 'bugpoint-reduced-simplified.bc'
source_filename = "_typed_vcat"
target datalayout = "e-m:e-i64:64-n32:64"
target triple = "powerpc64le-unknown-linux-gnu"

define void @julia__typed_vcat_20() {
top:
  %.sroa.6.0.copyload = load i64, i64 addrspace(11)* null, align 8
  %0 = call { i64, i1 } @llvm.ssub.with.overflow.i64(i64 %.sroa.6.0.copyload, i64 0)
  %1 = extractvalue { i64, i1 } %0, 0
  br label %L139

L139:                                             ; preds = %L139, %top
  %value_phi21 = phi i64 [ %5, %L139 ], [ 1, %top ]
  %value_phi23 = phi i64 [ 0, %L139 ], [ 1, %top ]
  %2 = add nsw i64 %value_phi23, -1
  %3 = add i64 %2, 0
  %4 = sitofp i64 %3 to half
  store half %4, half addrspace(13)* undef, align 2
  %.not101.not = icmp eq i64 %value_phi21, 0
  %5 = add i64 %value_phi21, 1
  br i1 %.not101.not, label %pass.1, label %L139

pass.1:                                           ; preds = %L139
  unreachable
}

; Function Attrs: nounwind readnone speculatable willreturn
declare { i64, i1 } @llvm.ssub.with.overflow.i64(i64, i64) #0

attributes #0 = { nounwind readnone speculatable willreturn }

!llvm.module.flags = !{!0}

!0 = !{i32 1, !"Debug Info Version", i32 3}

[vchuravy@service0001 ctr]$ ../usr/tools/llc -mcpu pwr9 bugpoint-reduced-simplified.ll   
[vchuravy@service0001 ctr]$ ../usr/tools/llc -mcpu pwr8 bugpoint-reduced-simplified.ll                                                                                                                                                        
Invalid PPC CTR loop!
UNREACHABLE executed at /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Target/PowerPC/PPCCTRLoops.cpp:214!
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0.      Program arguments: ../usr/tools/llc -mcpu pwr8 bugpoint-reduced-simplified.ll 
1.      Running pass 'Function Pass Manager' on module 'bugpoint-reduced-simplified.ll'.
2.      Running pass 'PowerPC CTR Loops Verify' on function '@julia__typed_vcat_20'
 #0 0x00007fff92ca622c llvm::sys::PrintStackTrace(llvm::raw_ostream&) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Support/Unix/Signals.inc:564:22
 #1 0x00007fff92ca6360 PrintStackTraceSignalHandler(void*) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Support/Unix/Signals.inc:624:23
 #2 0x00007fff92ca3b44 llvm::sys::RunSignalHandlers() /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Support/Signals.cpp:67:22
 #3 0x00007fff92ca47f4 SignalHandler(int) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Support/Unix/Signals.inc:396:31
 #4 0x00007fff973504d8  0x4d8 abort
 #5 0x00007fff973504d8 
 #6 0x00007fff973504d8 llvm::llvm_unreachable_internal(char const*, char const*, unsigned int) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Support/ErrorHandling.cpp:210:8
 #7 0x00007fff91ae2094 (anonymous namespace)::PPCCTRLoopsVerify::runOnMachineFunction(llvm::MachineFunction&) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/Target/PowerPC/PPCCTRLoops.cpp:214:11
 #8 0x00007fff92babb54 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.48) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/CodeGen/MachineFunctionPass.cpp:73:33
 #9 0x00007fff9522eea4 llvm::FPPassManager::runOnFunction(llvm::Function&) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/IR/LegacyPassManager.cpp:1516:40
#10 0x00007fff9313101c llvm::FPPassManager::runOnModule(llvm::Module&) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/IR/LegacyPassManager.cpp:1552:29
#11 0x00007fff92e4e470 runOnModule /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/IR/LegacyPassManager.cpp:1617:38
#12 0x00007fff92e4e470 llvm::legacy::PassManagerImpl::run(llvm::Module&) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/IR/LegacyPassManager.cpp:614:55
#13 0x00007fff92e4f028 llvm::legacy::PassManager::run(llvm::Module&) /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/lib/IR/LegacyPassManager.cpp:1737:17
#14 0x00007fff92e4dc90 compileModule /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/tools/llc/llc.cpp:650:11
#15 0x00007fff92e4dc90 main /nobackup/users/vchuravy/dev/julia/deps/srccache/llvm-11.0.0/tools/llc/llc.cpp:360:35
#16 0x00007fff92e4e0ac generic_start_main.isra.0 (/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so+0xdfe0ac)
#17 0x000000001000abf4 __libc_start_main (../usr/tools/llc+0x1000abf4)
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm3sys15PrintStackTraceERNS_11raw_ostreamE+0x3c)[0x7fff92ca622c]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(+0xc56360)[0x7fff92ca6360]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm3sys17RunSignalHandlersEv+0x84)[0x7fff92ca3b44]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(+0xc547f4)[0x7fff92ca47f4]
[0x7fff973504d8]
/lib64/libc.so.6(abort+0x2b4)[0x7fff91ae2094]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm25llvm_unreachable_internalEPKcS1_j+0xc4)[0x7fff92babb54]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(+0x31deea4)[0x7fff9522eea4]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(+0x10e101c)[0x7fff9313101c]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE+0x390)[0x7fff92e4e470]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm13FPPassManager11runOnModuleERNS_6ModuleE+0x48)[0x7fff92e4f028]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm6legacy15PassManagerImpl3runERNS_6ModuleE+0x420)[0x7fff92e4dc90]
/nobackup/users/vchuravy/dev/julia/jl-pwr8/usr/tools/../lib/libLLVM-11jl.so(_ZN4llvm6legacy11PassManager3runERNS_6ModuleE+0x1c)[0x7fff92e4e0ac]
../usr/tools/llc(main+0x1b94)[0x1000abf4]
/lib64/libc.so.6(+0x25200)[0x7fff91ac5200]
/lib64/libc.so.6(__libc_start_main+0xc4)[0x7fff91ac53f4]
Aborted

Reported upstream as https://bugs.llvm.org/show_bug.cgi?id=48519