[llvm-bugs] [Bug 43326] New: loop-interchange crashes: Assertion `OuterInnerReductions.find(PHI) != OuterInnerReductions.end() && "Expected a reduction PHI node"' failed.

Mon Sep 16 05:13:52 PDT 2019

https://bugs.llvm.org/show_bug.cgi?id=43326

            Bug ID: 43326
           Summary: loop-interchange crashes: Assertion
                    `OuterInnerReductions.find(PHI) !=
                    OuterInnerReductions.end() && "Expected a reduction
                    PHI node"' 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 22508
  --> https://bugs.llvm.org/attachment.cgi?id=22508&action=edit
.bc file of the source code

$clang -v
clang version 10.0.0 (trunk 371952)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
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/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

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

$opt -instcombine -loop-rotate -sroa -licm -loop-interchange small.bc -o
small-opt.bc
opt:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/lib/Transforms/Scalar/LoopInterchange.cpp:1544:
bool {anonymous}::LoopInterchangeTransform::adjustLoopBranches(): Assertion
`OuterInnerReductions.find(PHI) != OuterInnerReductions.end() && "Expected a
reduction PHI node"' failed.
Stack dump:
0.      Program arguments:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt -instcombine
-loop-rotate -sroa -licm -loop-interchange small.bc -o small-opt.bc 
1.      Running pass 'Function Pass Manager' on module 'small.bc'.
2.      Running pass 'Loop Pass Manager' on function '@f'
3.      Running pass 'Interchanges loops for cache reuse' on basic block
'%for.body'
 #0 0x000055c7ba9d327a llvm::sys::PrintStackTrace(llvm::raw_ostream&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x277727a)
 #1 0x000055c7ba9d0f54 llvm::sys::RunSignalHandlers()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2774f54)
 #2 0x000055c7ba9d1092 SignalHandler(int)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2775092)
 #3 0x00007f093d139890 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
 #4 0x00007f093bdebe97 raise
/build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #5 0x00007f093bded801 abort /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
 #6 0x00007f093bddd39a __assert_fail_base
/build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
 #7 0x00007f093bddd412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
 #8 0x000055c7ba7c755a (anonymous
namespace)::LoopInterchangeTransform::transform()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x256b55a)
 #9 0x000055c7ba7c9935 (anonymous
namespace)::LoopInterchange::processLoopList(llvm::SmallVector<llvm::Loop*,
8u>) (/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x256d935)
#10 0x000055c7ba7ca57d (anonymous
namespace)::LoopInterchange::runOnLoop(llvm::Loop*, llvm::LPPassManager&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x256e57d)
#11 0x000055c7b9ca642b llvm::LPPassManager::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x1a4a42b)
#12 0x000055c7ba312de9 llvm::FPPassManager::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6de9)
#13 0x000055c7ba312ee1 llvm::FPPassManager::runOnModule(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6ee1)
#14 0x000055c7ba312041 llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6041)
#15 0x000055c7b8aeb74f main
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x88f74f)
#16 0x00007f093bdceb97 __libc_start_main
/build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
#17 0x000055c7b8b6354a _start
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x90754a)
Aborted (core dumped)

By using bugpoint, the optimization sequences can be reduced to
"-loop-interchange".

$opt bugpoint-reduced-simplified.bc -loop-interchange
opt:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/lib/Transforms/Scalar/LoopInterchange.cpp:1544:
bool {anonymous}::LoopInterchangeTransform::adjustLoopBranches(): Assertion
`OuterInnerReductions.find(PHI) != OuterInnerReductions.end() && "Expected a
reduction PHI node"' failed.
Stack dump:
0.      Program arguments:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt
bugpoint-reduced-simplified.bc -loop-interchange 
1.      Running pass 'Function Pass Manager' on module
'bugpoint-reduced-simplified.bc'.
2.      Running pass 'Loop Pass Manager' on function '@f'
3.      Running pass 'Interchanges loops for cache reuse' on basic block
'%for.body3'
 #0 0x0000556e9772c27a llvm::sys::PrintStackTrace(llvm::raw_ostream&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x277727a)
 #1 0x0000556e97729f54 llvm::sys::RunSignalHandlers()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2774f54)
 #2 0x0000556e9772a092 SignalHandler(int)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2775092)
 #3 0x00007f6427256890 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
 #4 0x00007f6425f08e97 raise
/build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #5 0x00007f6425f0a801 abort /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
 #6 0x00007f6425efa39a __assert_fail_base
/build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
 #7 0x00007f6425efa412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
 #8 0x0000556e9752055a (anonymous
namespace)::LoopInterchangeTransform::transform()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x256b55a)
 #9 0x0000556e97522935 (anonymous
namespace)::LoopInterchange::processLoopList(llvm::SmallVector<llvm::Loop*,
8u>) (/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x256d935)
#10 0x0000556e9752357d (anonymous
namespace)::LoopInterchange::runOnLoop(llvm::Loop*, llvm::LPPassManager&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x256e57d)
#11 0x0000556e969ff42b llvm::LPPassManager::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x1a4a42b)
#12 0x0000556e9706bde9 llvm::FPPassManager::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6de9)
#13 0x0000556e9706bee1 llvm::FPPassManager::runOnModule(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6ee1)
#14 0x0000556e9706b041 llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6041)
#15 0x0000556e9584474f main
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x88f74f)
#16 0x00007f6425eebb97 __libc_start_main
/build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
#17 0x0000556e958bc54a _start
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x90754a)
Aborted (core dumped)

---------------------------------------
int a, c, d;
char b;
int e[][1];
void f() {
  for (; a; a++) {
    b = 0;
    for (; b >= 0; b--) {
      c = 0;
      for (; c <= 0; c++) {
        int *g = &d;
        *g ^= e[c][b];
      }
    }
  }
}

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