Extended Description

OS and Platform:
CentOS Linux release 7.8.2003 (Core), x86_64 GNU/Linux

Program:
$ cat a.c
short a=0;
int b=0, d=0, f=0;
long c=0;
char e=0;
int main() {
int g = 3;
for (; a;) {
int h = 0;
for (;; d) {
c = (h <= 0) << 8;
h = b;
for (; g;)
;
for (; f;)
for (; e;)
;
}
}
return 0;
}

clang version:
$ clang --version
clang version 12.0.0 (/home/suocy/src/llvm-dev/llvm-project/llvm/tools/clang e52a91e)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/suocy/bin/llvm-dev/bin

Command Lines:
$ clang -O3 -mllvm -disable-llvm-optzns -c -emit-llvm a.c -o a.bc
a.c:9:13: warning: expression result unused [-Wunused-value]
for (;; d) {
^
1 warning generated.
$ opt -mem2reg -deadargelim -simplifycfg -inline -sroa -early-cse-memssa -jump-threading -instcombine a.bc -o a.opt.bc
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: /home/suocy/bin/llvm-dev/bin/opt -mem2reg -deadargelim -simplifycfg -inline -sroa -early-cse-memssa -jump-threading -instcombine a.bc -o a.opt.bc

1.  Running pass 'CallGraph Pass Manager' on module 'a.bc'.
   

2.  Running pass 'Combine redundant instructions' on function '@main'
   

#​0 0x0000000002a8136c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/suocy/bin/llvm-dev/bin/opt+0x2a8136c)
#​1 0x0000000002a7f1e4 llvm::sys::RunSignalHandlers() (/home/suocy/bin/llvm-dev/bin/opt+0x2a7f1e4)
#​2 0x0000000002a7f343 SignalHandler(int) (/home/suocy/bin/llvm-dev/bin/opt+0x2a7f343)
#​3 0x00007fec2e9b4630 __restore_rt (/lib64/libpthread.so.0+0xf630)
#​4 0x0000000002584f5e llvm::InstCombinerImpl::visitSelectInst(llvm::SelectInst&) (/home/suocy/bin/llvm-dev/bin/opt+0x2584f5e)
#​5 0x00000000024f310a llvm::InstCombinerImpl::run() (/home/suocy/bin/llvm-dev/bin/opt+0x24f310a)
#​6 0x00000000024f4d29 combineInstructionsOverFunction(llvm::Function&, llvm::InstCombineWorklist&, llvm::AAResults*, llvm::AssumptionCache&, llvm::TargetLibraryInfo&, llvm::TargetTransformInfo&, llvm::DominatorTree&, llvm::OptimizationRemarkEmitter&, llvm::BlockFrequencyInfo*, llvm::ProfileSummaryInfo*, unsigned int, llvm::LoopInfo*) (/home/suocy/bin/llvm-dev/bin/opt+0x24f4d29)
#​7 0x00000000024f698a llvm::InstructionCombiningPass::runOnFunction(llvm::Function&) (/home/suocy/bin/llvm-dev/bin/opt+0x24f698a)
#​8 0x00000000022bf598 llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/suocy/bin/llvm-dev/bin/opt+0x22bf598)
#​9 0x0000000001a304f4 (anonymous namespace)::CGPassManager::runOnModule(llvm::Module&) (/home/suocy/bin/llvm-dev/bin/opt+0x1a304f4)
#​10 0x00000000022bee43 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/suocy/bin/llvm-dev/bin/opt+0x22bee43)
#​11 0x000000000072c61b main (/home/suocy/bin/llvm-dev/bin/opt+0x72c61b)
#​12 0x00007fec2d58e555 __libc_start_main (/lib64/libc.so.6+0x22555)
#​13 0x00000000007ddac5 _start (/home/suocy/bin/llvm-dev/bin/opt+0x7ddac5)
Segmentation fault