[llvm-bugs] [Bug 49571] New: loop-flatten pass crashes: Assertion `InductionPHI->getIncomingValueForBlock(Latch) == Increment && "PHI value is not increment inst"' failed.

Sat Mar 13 00:37:48 PST 2021

https://bugs.llvm.org/show_bug.cgi?id=49571

            Bug ID: 49571
           Summary: loop-flatten pass crashes: Assertion
                    `InductionPHI->getIncomingValueForBlock(Latch) ==
                    Increment && "PHI value is not increment inst"'
                    failed.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: cszide at 163.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 24636
  --> https://bugs.llvm.org/attachment.cgi?id=24636&action=edit
small.bc

$clang -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
77394c12a48822bb7a9183408f922d90c1d563cd)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Selected multilib: .;@m64

$clang -O3 -c -emit-llvm -femit-all-decls -mllvm -disable-llvm-optzns small.c
-o small.bc

$opt -sroa -loop-rotate  -break-crit-edges -loop-reduce -loop-rotate
-loop-flatten  small.bc -o small-opt.bc
opt:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/llvm/lib/Transforms/Scalar/LoopFlatten.cpp:180:
bool findLoopComponents(llvm::Loop*,
llvm::SmallPtrSetImpl<llvm::Instruction*>&, llvm::PHINode*&, llvm::Value*&,
llvm::BinaryOperator*&, llvm::BranchInst*&, llvm::ScalarEvolution*): Assertion
`InductionPHI->getIncomingValueForBlock(Latch) == Increment && "PHI value is
not increment inst"' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash
backtrace.
Stack dump:
0.      Program arguments:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt -sroa
-loop-rotate -break-crit-edges -loop-reduce -loop-rotate -loop-flatten small.bc
-o small-opt.bc
1.      Running pass 'Function Pass Manager' on module 'small.bc'.
2.      Running pass 'Flattens loops' on function '@main'
 #0 0x0000562077e8a5ec llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x2e865ec)
 #1 0x0000562077e882b4 llvm::sys::RunSignalHandlers()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x2e842b4)
 #2 0x0000562077e88423 SignalHandler(int) Signals.cpp:0:0
 #3 0x00007f4681f148a0 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x128a0)
 #4 0x00007f4680b7bf47 raise
/build/glibc-2ORdQG/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #5 0x00007f4680b7d8b1 abort /build/glibc-2ORdQG/glibc-2.27/stdlib/abort.c:81:0
 #6 0x00007f4680b6d42a __assert_fail_base
/build/glibc-2ORdQG/glibc-2.27/assert/assert.c:89:0
 #7 0x00007f4680b6d4a2 (/lib/x86_64-linux-gnu/libc.so.6+0x304a2)
 #8 0x0000562077c17d58 findLoopComponents(llvm::Loop*,
llvm::SmallPtrSetImpl<llvm::Instruction*>&, llvm::PHINode*&, llvm::Value*&,
llvm::BinaryOperator*&, llvm::BranchInst*&, llvm::ScalarEvolution*)
LoopFlatten.cpp:0:0
 #9 0x0000562077c184fd CanFlattenLoopPair(FlattenInfo&, llvm::DominatorTree*,
llvm::LoopInfo*, llvm::ScalarEvolution*, llvm::AssumptionCache*,
llvm::TargetTransformInfo const*) (.isra.325) LoopFlatten.cpp:0:0
#10 0x0000562077c19d75 Flatten(llvm::DominatorTree*, llvm::LoopInfo*,
llvm::ScalarEvolution*, llvm::AssumptionCache*, llvm::TargetTransformInfo*)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x2c15d75)
#11 0x0000562077639918 llvm::FPPassManager::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x2635918)
#12 0x000056207763a449 llvm::FPPassManager::runOnModule(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x2636449)
#13 0x0000562077639196 llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x2635196)
#14 0x000056207597ac0d main
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0x976c0d)
#15 0x00007f4680b5eb97 __libc_start_main
/build/glibc-2ORdQG/glibc-2.27/csu/../csu/libc-start.c:344:0
#16 0x0000562075a43eaa _start
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/bin/opt+0xa3feaa)
Aborted (core dumped)

The source code of small.c is as follows.
--------------------------------------------------------
void main() {
  int a;
  for (;;) {
    a = 0;
    for (; a < 10; a++)
      printf("", a);
  }
}

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