[llvm-bugs] [Bug 48276] New: opt crashes with "opt -sroa -lcssa -loop-unswitch": Assertion `L->isRecursivelyLCSSAForm(*DT, *LI) && "Requested to preserve LCSSA, but it's already broken."' failed.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48276

            Bug ID: 48276
           Summary: opt crashes with "opt -sroa -lcssa -loop-unswitch":
                    Assertion `L->isRecursivelyLCSSAForm(*DT, *LI) &&
                    "Requested to preserve LCSSA, but it's already
                    broken."' failed.
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: suochenyao at 163.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

*******************************************************************************
OS and Platform:
CentOS Linux release 7.8.2003 (Core), x86_64 GNU/Linux
*******************************************************************************
Program:
int a=0;
char b(c) {
  for (; 0;) {
    int d=0;
    c = 0;
    if (d)
      continue;
  }
  for (; 1;)
    ;
  int e=0;
f:
  if (e) {
    int g=0;
    if (c)
      goto f;
    for (; 0; b)
      return 0;
  } else
    for (; 0;)
      for (; 0; 1)
        return a;
}
int main() {}
*******************************************************************************
clang version:
$ clang -v
clang version 12.0.0 (/home/suocy/src/llvm-dev/llvm-project/llvm/tools/clang
95956c1c9aae7ea21c2b2f7a21e0901d549bd190)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/suocy/bin/llvm-dev/bin
Found candidate GCC installation:
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Selected GCC installation:
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
*******************************************************************************
How to reproduce:
$ clang -O3 -mllvm -disable-llvm-optzns -c -emit-llvm a.c -o a.bc
$ opt -sroa -lcssa -loop-unswitch a.bc -o a.opt.bc
*******************************************************************************
Command Lines:
$ clang -O3 -mllvm -disable-llvm-optzns -c -emit-llvm a.c -o a.bc
a.c:17:15: warning: expression result unused [-Wunused-value]
    for (; 0; b)
              ^
a.c:21:17: warning: expression result unused [-Wunused-value]
      for (; 0; 1)
                ^
2 warnings generated.
$ opt -sroa -lcssa -loop-unswitch a.bc -o a.opt.bc
opt:
/home/suocy/src/llvm-dev/llvm-project/llvm/lib/Transforms/Utils/LoopSimplify.cpp:740:
bool llvm::simplifyLoop(llvm::Loop*, llvm::DominatorTree*, llvm::LoopInfo*,
llvm::ScalarEvolution*, llvm::AssumptionCache*, llvm::MemorySSAUpdater*, bool):
Assertion `L->isRecursivelyLCSSAForm(*DT, *LI) && "Requested to preserve LCSSA,
but it's already broken."' failed.
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 -sroa -lcssa
-loop-unswitch a.bc -o a.opt.bc
1.      Running pass 'Function Pass Manager' on module 'a.bc'.
2.      Running pass 'Canonicalize natural loops' on function '@b'
 #0 0x0000000002a7216c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
(/home/suocy/bin/llvm-dev/bin/opt+0x2a7216c)
 #1 0x0000000002a6ffe4 llvm::sys::RunSignalHandlers()
(/home/suocy/bin/llvm-dev/bin/opt+0x2a6ffe4)
 #2 0x0000000002a70143 SignalHandler(int)
(/home/suocy/bin/llvm-dev/bin/opt+0x2a70143)
 #3 0x00007f545bb8c630 __restore_rt (/lib64/libpthread.so.0+0xf630)
 #4 0x00007f545a77a387 raise (/lib64/libc.so.6+0x36387)
 #5 0x00007f545a77ba78 abort (/lib64/libc.so.6+0x37a78)
 #6 0x00007f545a7731a6 __assert_fail_base (/lib64/libc.so.6+0x2f1a6)
 #7 0x00007f545a773252 (/lib64/libc.so.6+0x2f252)
 #8 0x0000000002b4288d llvm::simplifyLoop(llvm::Loop*, llvm::DominatorTree*,
llvm::LoopInfo*, llvm::ScalarEvolution*, llvm::AssumptionCache*,
llvm::MemorySSAUpdater*, bool) (/home/suocy/bin/llvm-dev/bin/opt+0x2b4288d)
 #9 0x0000000002b42b0d (anonymous
namespace)::LoopSimplify::runOnFunction(llvm::Function&)
(/home/suocy/bin/llvm-dev/bin/opt+0x2b42b0d)
#10 0x00000000022b2ac8 llvm::FPPassManager::runOnFunction(llvm::Function&)
(/home/suocy/bin/llvm-dev/bin/opt+0x22b2ac8)
#11 0x00000000022b3569 llvm::FPPassManager::runOnModule(llvm::Module&)
(/home/suocy/bin/llvm-dev/bin/opt+0x22b3569)
#12 0x00000000022b2373 llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/home/suocy/bin/llvm-dev/bin/opt+0x22b2373)
#13 0x000000000072b32b main (/home/suocy/bin/llvm-dev/bin/opt+0x72b32b)
#14 0x00007f545a766555 __libc_start_main (/lib64/libc.so.6+0x22555)
#15 0x00000000007dcd95 _start (/home/suocy/bin/llvm-dev/bin/opt+0x7dcd95)
Aborted

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