[LoopLoadElimination] Crash at -O2/3/s: unhandled irreducible control flow

Compiler Explorer: https://godbolt.org/z/1dTz533h1

small.ll

```llvm
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; Function Attrs: optsize
define i32 @d(i32 %e) #0 {
entry:
br label %a

a: ; preds = %for.cond4, %entry
br label %for.cond

for.cond: ; preds = %for.cond1, %a
br label %for.cond1

for.cond1: ; preds = %for.inc, %for.cond
%0 = phi i8 [ 0, %for.cond ], [ %inc, %for.inc ]
%cmp = icmp slt i8 %0, 4
br i1 %cmp, label %for.body, label %for.cond

for.body: ; preds = %for.cond1
%conv3 = sext i8 %0 to i32
%and = and i32 %e, %conv3
%cond = icmp eq i32 %and, 0
br i1 %cond, label %for.cond4, label %sw.default

for.cond4: ; preds = %for.body
%tobool.not = icmp eq i32 %e, 0
br i1 %tobool.not, label %for.inc, label %a

sw.default: ; preds = %for.body
ret i32 0

for.inc: ; preds = %for.cond4
%inc = add i8 %0, 1
br label %for.cond1
}

; Function Attrs: optsize
define void @main(i8 %0, i32 %conv) #0 {
entry:
br label %for.cond

for.cond: ; preds = %for.body, %entry
%tobool.not = icmp eq i8 %0, 0
br i1 %tobool.not, label %for.end, label %for.body

for.body: ; preds = %for.cond
%call = call i32 @d(i32 %conv)
br label %for.cond

for.end: ; preds = %for.cond
ret void
}

attributes #0 = { optsize }

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

!0 = !{i32 1, !"ProfileSummary", !1}
!1 = !{!2, !3, !4, !5, !6, !7, !8, !9, !10, !11}
!2 = !{!"ProfileFormat", !"InstrProf"}
!3 = !{!"TotalCount", i64 1}
!4 = !{!"MaxCount", i64 1}
!5 = !{!"MaxInternalCount", i64 0}
!6 = !{!"MaxFunctionCount", i64 1}
!7 = !{!"NumCounts", i64 10}
!8 = !{!"NumFunctions", i64 2}
!9 = !{!"IsPartialProfile", i64 0}
!10 = !{!"PartialProfileRatio", double 0.000000e+00}
!11 = !{!"DetailedSummary", !12}
!12 = !{!13, !14, !15, !16, !17, !18, !19, !20, !21, !22, !23, !24, !25, !26, !27, !28}
!13 = !{i32 10000, i64 0, i32 0}
!14 = !{i32 100000, i64 0, i32 0}
!15 = !{i32 200000, i64 0, i32 0}
!16 = !{i32 300000, i64 0, i32 0}
!17 = !{i32 400000, i64 0, i32 0}
!18 = !{i32 500000, i64 0, i32 0}
!19 = !{i32 600000, i64 0, i32 0}
!20 = !{i32 700000, i64 0, i32 0}
!21 = !{i32 800000, i64 0, i32 0}
!22 = !{i32 900000, i64 0, i32 0}
!23 = !{i32 950000, i64 0, i32 0}
!24 = !{i32 990000, i64 0, i32 0}
!25 = !{i32 999000, i64 0, i32 0}
!26 = !{i32 999900, i64 0, i32 0}
!27 = !{i32 999990, i64 0, i32 0}
!28 = !{i32 999999, i64 0, i32 0}
```

Reproduce:
```
$ opt -O3 small.ll -o /dev/null
unhandled irreducible control flow
UNREACHABLE executed at /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/Analysis/BlockFrequencyInfoImpl.h:1196!
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
Stack dump:
0. Program arguments: opt -O3 small.ll -o /dev/null
1. Running pass "function(drop-unnecessary-assumes,float2int,lower-constant-intrinsics,chr,loop(loop-rotate,loop-deletion),loop-distribute,inject-tli-mappings,loop-vectorize,drop-unnecessary-assumes,infer-alignment,loop-load-elim,instcombine,simplifycfg,slp-vectorizer,vector-combine,instcombine,loop-unroll,transform-warning,sroa,infer-alignment,instcombine,loop-mssa(licm),alignment-from-assumptions,loop-sink,instsimplify,div-rem-pairs,mergeicmps,expand-memcmp,tailcallelim,simplifycfg)" on module "small.ll"
2. Running pass "loop-load-elim" on function "main"
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0 opt 0x0000560ee645d617 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 39
1 opt 0x0000560ee645b2ba llvm::sys::RunSignalHandlers() + 154
2 opt 0x0000560ee645e4b5
3 libc.so.6 0x00007f7878e11520
4 libc.so.6 0x00007f7878e659fc pthread_kill + 300
5 libc.so.6 0x00007f7878e11476 raise + 22
6 libc.so.6 0x00007f7878df77f3 abort + 211
7 opt 0x0000560ee63bc001
8 opt 0x0000560ee59e36d0 llvm::BlockFrequencyInfoImpl::calculate(llvm::Function const&, llvm::BranchProbabilityInfo const&, llvm::LoopInfo const&) + 656
9 opt 0x0000560ee59e302e llvm::BlockFrequencyInfo::calculate(llvm::Function const&, llvm::BranchProbabilityInfo const&, llvm::LoopInfo const&) + 190
10 opt 0x0000560ee59e51df llvm::BlockFrequencyAnalysis::run(llvm::Function&, llvm::AnalysisManager&) + 207
11 opt 0x0000560ee422043f
12 opt 0x0000560ee6242808 llvm::AnalysisManager::getResultImpl(llvm::AnalysisKey*, llvm::Function&) + 520
13 opt 0x0000560ee54fe49f llvm::LoopLoadEliminationPass::run(llvm::Function&, llvm::AnalysisManager&) + 639
14 opt 0x0000560ee424472d
15 opt 0x0000560ee6240197 llvm::PassManager>::run(llvm::Function&, llvm::AnalysisManager&) + 407
16 opt 0x0000560ee29eb2fd
17 opt 0x0000560ee6243cde llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager&) + 478
18 opt 0x0000560ee25199ed
19 opt 0x0000560ee623f277 llvm::PassManager>::run(llvm::Module&, llvm::AnalysisManager&) + 407
20 opt 0x0000560ee25115af llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef, llvm::ArrayRef>, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool, bool, bool, bool) + 11455
21 opt 0x0000560ee2507478 optMain + 9832
22 libc.so.6 0x00007f7878df8d90
23 libc.so.6 0x00007f7878df8e40 __libc_start_main + 128
24 opt 0x0000560ee2504735 _start + 37
[1] 3734788 IOT instruction (core dumped) opt -O3 small.ll -o /dev/null
```

C reproducer:

small.c
```c
char c;
unsigned b;
unsigned d(unsigned e) {
a:
for (;;) {
c = 0;
for (; c <= 3; c++)
switch (c & e) {
case 0:
for (; b;)
goto a;
break;
default:
return e;
}
}
}
void main() {
for (; c;)
d(c);
}
```

Reproduce at -Os:
```
$ clang-trunk -O3 -fprofile-instr-generate small.c
$ LLVM_PROFILE_FILE="test.profraw" ./a.out
$ llvm-profdata merge -o test.profdata test.profraw
$ clang-trunk -Os -fprofile-instr-use=test.profdata small.c
```
Crash:
```
unhandled irreducible control flow
UNREACHABLE executed at /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/Analysis/BlockFrequencyInfoImpl.h:1196!
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0. Program arguments: /data/x27zhou/compiler-nightly/install/llvm/bin/clang-23 -cc1 -triple x86_64-unknown-linux-gnu -Os -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name small.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/home/x27zhou/fuzz-pgo/PGOFuzz/pgofuzz2-output-2026-04-10-04-06-53/crash-clang-trunk-78805/perses_result -fprofile-instrument-use=clang -fprofile-instrument-use-path=test.profdata -fcoverage-compilation-dir=/home/x27zhou/fuzz-pgo/PGOFuzz/pgofuzz2-output-2026-04-10-04-06-53/crash-clang-trunk-78805/perses_result -resource-dir /data/x27zhou/compiler-nightly/install/llvm/lib/clang/23 -internal-isystem /data/x27zhou/compiler-nightly/install/llvm/lib/clang/23/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/12/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -ferror-limit 19 -fmessage-length=180 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcolor-diagnostics -vectorize-loops -vectorize-slp -faddrsig -fdwarf2-cfi-asm -o /tmp/small-a1412c.o -x c small.c
1. parser at end of file
2. Optimizer
3. Running pass "function(drop-unnecessary-assumes,float2int,lower-constant-intrinsics,loop(loop-rotate,loop-deletion),loop-distribute,inject-tli-mappings,loop-vectorize,drop-unnecessary-assumes,infer-alignment,loop-load-elim,instcombine,simplifycfg,slp-vectorizer,vector-combine,instcombine,loop-unroll,transform-warning,sroa,infer-alignment,instcombine,loop-mssa(licm),alignment-from-assumptions,loop-sink,instsimplify,div-rem-pairs,mergeicmps,expand-memcmp,tailcallelim,simplifycfg)" on module "small.c"
4. Running pass "loop-load-elim" on function "main"
#0 0x00005601c2f15277 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Support/Unix/Signals.inc:880:13
#1 0x00005601c2f12f1a llvm::sys::RunSignalHandlers() /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Support/Signals.cpp:109:18
#2 0x00005601c2f16115 SignalHandler(int, siginfo_t*, void*) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Support/Unix/Signals.inc:448:38
#3 0x00005601c2f15f78 int const* std::__find_if>(int const*, int const*, __gnu_cxx::__ops::_Iter_equals_val, std::random_access_iterator_tag) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_algobase.h:2067:8
#4 0x00005601c2f15f78 int const* std::__find_if>(int const*, int const*, __gnu_cxx::__ops::_Iter_equals_val) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_algobase.h:2112:14
#5 0x00005601c2f15f78 int const* std::find(int const*, int const*, int const&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_algo.h:3851:14
#6 0x00005601c2f15f78 bool llvm::is_contained(int const (&) [10], int const&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/ADT/STLExtras.h:1953:12
#7 0x00005601c2f15f78 SignalHandlerTerminate(int, siginfo_t*, void*) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Support/Unix/Signals.inc:464:7
#8 0x00007f824a363520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#9 0x00007f824a3b79fc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#10 0x00007f824a3b79fc __pthread_kill_internal ./nptl/pthread_kill.c:78:10
#11 0x00007f824a3b79fc pthread_kill ./nptl/pthread_kill.c:89:10
#12 0x00007f824a363476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
#13 0x00007f824a3497f3 abort ./stdlib/abort.c:81:7
#14 0x00005601c2e84701 (/data/x27zhou/compiler-nightly/install/llvm/bin/clang-23+0x3a0f701)
#15 0x00005601c1fe9a70 llvm::BlockFrequencyInfoImpl::computeMassInFunction() /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/Analysis/BlockFrequencyInfoImpl.h:1294:7
#16 0x00005601c1fe9a70 llvm::BlockFrequencyInfoImpl::calculate(llvm::Function const&, llvm::BranchProbabilityInfo const&, llvm::LoopInfo const&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/Analysis/BlockFrequencyInfoImpl.h:1070:3
#17 0x00005601c1fe93ce llvm::BlockFrequencyInfo::calculate(llvm::Function const&, llvm::BranchProbabilityInfo const&, llvm::LoopInfo const&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Analysis/BlockFrequencyInfo.cpp:190:35
#18 0x00005601c1feb57f llvm::BlockFrequencyAnalysis::run(llvm::Function&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Analysis/BlockFrequencyInfo.cpp:338:1
#19 0x00005601c3e79dcf std::__detail::_MakeUniq::Invalidator, true>>::__single_object std::make_unique::Invalidator, true>, llvm::BlockFrequencyInfo>(llvm::BlockFrequencyInfo&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/unique_ptr.h:1065:30
#20 0x00005601c3e79dcf llvm::detail::AnalysisPassModel::Invalidator>::run(llvm::Function&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerInternal.h:315:12
#21 0x00005601c2966768 std::__cxx11::list::Invalidator>, std::default_delete::Invalidator>>>>, std::allocator::Invalidator>, std::default_delete::Invalidator>>>>>>::end() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_list.h:1043:25
#22 0x00005601c2966768 std::pair::Invalidator>, std::default_delete::Invalidator>>>>& std::__cxx11::list::Invalidator>, std::default_delete::Invalidator>>>>, std::allocator::Invalidator>, std::default_delete::Invalidator>>>>>>::emplace_back::Invalidator>, std::default_delete::Invalidator>>>>(llvm::AnalysisKey*&, std::unique_ptr::Invalidator>, std::default_delete::Invalidator>>>&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_list.h:1321:20
#23 0x00005601c2966768 llvm::AnalysisManager::getResultImpl(llvm::AnalysisKey*, llvm::Function&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerImpl.h:148:16
#24 0x00005601c64d583f llvm::BlockFrequencyAnalysis::Result& llvm::AnalysisManager::getResult(llvm::Function&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManager.h:421:55
#25 0x00005601c64d583f llvm::LoopLoadEliminationPass::run(llvm::Function&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp:695:11
#26 0x00005601c3e968bd llvm::detail::PassModel>::run(llvm::Function&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerInternal.h:91:5
#27 0x00005601c2963fd7 llvm::PassManager>::run(llvm::Function&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerImpl.h:80:8
#28 0x00005601c07fac2d llvm::detail::PassModel>, llvm::AnalysisManager>::run(llvm::Function&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerInternal.h:91:5
#29 0x00005601c2967c3e llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/lib/IR/PassManager.cpp:132:23
#30 0x00005601c07fb8cd llvm::detail::PassModel>::run(llvm::Module&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerInternal.h:91:5
#31 0x00005601c29630b7 llvm::PassManager>::run(llvm::Module&, llvm::AnalysisManager&) /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/PassManagerImpl.h:80:8
#32 0x00005601c327000e llvm::SmallPtrSetImplBase::isSmall() const /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/ADT/SmallPtrSet.h:248:33
#33 0x00005601c327000e llvm::SmallPtrSetImplBase::~SmallPtrSetImplBase() /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/ADT/SmallPtrSet.h:89:10
#34 0x00005601c327000e llvm::PreservedAnalyses::~PreservedAnalyses() /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/IR/Analysis.h:112:7
#35 0x00005601c327000e (anonymous namespace)::EmitAssemblyHelper::RunOptimizationPipeline(clang::BackendAction, std::unique_ptr>&, std::unique_ptr>&, clang::BackendConsumer*) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1209:5
#36 0x00005601c3267ae6 (anonymous namespace)::EmitAssemblyHelper::RunCodegenPipeline(clang::BackendAction, std::unique_ptr>&, std::unique_ptr>&) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1218:7
#37 0x00005601c3267ae6 (anonymous namespace)::EmitAssemblyHelper::emitAssembly(clang::BackendAction, std::unique_ptr>, clang::BackendConsumer*) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1301:3
#38 0x00005601c3267ae6 clang::emitBackendOutput(clang::CompilerInstance&, clang::CodeGenOptions&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr, std::unique_ptr>, clang::BackendConsumer*) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1477:13
#39 0x00005601c37dbd03 std::unique_ptr>::~unique_ptr() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/unique_ptr.h:395:6
#40 0x00005601c37dbd03 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/CodeGen/CodeGenAction.cpp:312:3
#41 0x00005601c4d49b87 __gnu_cxx::__normal_iterator>*, std::vector>, std::allocator>>>>::__normal_iterator(std::unique_ptr>* const&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_iterator.h:1073:20
#42 0x00005601c4d49b87 std::vector>, std::allocator>>>::begin() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/stl_vector.h:869:16
#43 0x00005601c4d49b87 void clang::finalize>, std::allocator>>>>(std::vector>, std::allocator>>>&, clang::Sema const&) /data/x27zhou/compiler-nightly/src/llvm-project/clang/include/clang/Sema/TemplateInstCallback.h:54:16
#44 0x00005601c4d49b87 clang::ParseAST(clang::Sema&, bool, bool) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/Parse/ParseAST.cpp:190:3
#45 0x00005601c3a68856 clang::FrontendAction::Execute() /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1346:10
#46 0x00005601c39d690f llvm::Error::getPtr() const /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/Support/Error.h:278:42
#47 0x00005601c39d690f llvm::Error::operator bool() /data/x27zhou/compiler-nightly/src/llvm-project/llvm/include/llvm/Support/Error.h:241:16
#48 0x00005601c39d690f clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/Frontend/CompilerInstance.cpp:990:23
#49 0x00005601c3b5fb05 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) /data/x27zhou/compiler-nightly/src/llvm-project/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:318:25
#50 0x00005601c03eb018 cc1_main(llvm::ArrayRef, char const*, void*) /data/x27zhou/compiler-nightly/src/llvm-project/clang/tools/driver/cc1_main.cpp:302:15
#51 0x00005601c03e7500 ExecuteCC1Tool(llvm::SmallVectorImpl&, llvm::ToolContext const&, llvm::IntrusiveRefCntPtr) /data/x27zhou/compiler-nightly/src/llvm-project/clang/tools/driver/driver.cpp:229:12
#52 0x00005601c03e65fc clang_main(int, char**, llvm::ToolContext const&) /data/x27zhou/compiler-nightly/src/llvm-project/clang/tools/driver/driver.cpp:277:12
#53 0x00005601c03f64dd main /data/x27zhou/compiler-nightly/build/llvm/tools/clang/tools/driver/clang-driver.cpp:17:10
#54 0x00007f824a34ad90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#55 0x00007f824a34ae40 call_init ./csu/../csu/libc-start.c:128:20
#56 0x00007f824a34ae40 __libc_start_main ./csu/../csu/libc-start.c:379:5
#57 0x00005601c03e4dc5 _start (/data/x27zhou/compiler-nightly/install/llvm/bin/clang-23+0xf6fdc5)
clang-trunk: error: unable to execute command: Aborted (core dumped)
clang-trunk: error: clang frontend command failed with exit code -2 (use -v to see invocation)
clang version 23.0.0git (https://github.com/llvm/llvm-project.git 9116344c02bf0b9ec037451d12935d7539c48679)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /data/x27zhou/compiler-nightly/install/llvm/bin
Build config: +assertions
clang-trunk: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-trunk: note: diagnostic msg: /tmp/small-346d77.c
clang-trunk: note: diagnostic msg: /tmp/small-346d77.sh
clang-trunk: note: diagnostic msg:

********************
[1] 3847809 IOT instruction (core dumped) clang-trunk -Os -fprofile-instr-use=test.profdata small.c
```
Label: generated by fuzzer

Start by running `opt -O3 small.ll -o /dev/null` and inspect `llvm/include/llvm/Analysis/BlockFrequencyInfoImpl.h` around line 1196. Trace `LoopLoadEliminationPass` on function `main`, then reproduce with `small.c` and the shown profile-guided commands if needed. Done means the irreducible-control-flow crash no longer occurs at the reported optimization levels, with coverage for the reproducer.

Written by the indexing model from the issue text.