<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - instcombine crashes: Assertion `!empty()' failed."
   href="https://bugs.llvm.org/show_bug.cgi?id=43347">43347</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>instcombine crashes: Assertion `!empty()' failed.
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Scalar Optimizations
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>cszide@163.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=22517" name="attach_22517" title=".bc file of the source code">attachment 22517</a> <a href="attachment.cgi?id=22517&action=edit" title=".bc file of the source code">[details]</a></span>
.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 -loop-rotate -partial-inliner -strip -instcombine small.bc -o small-opt.bc
opt:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/include/llvm/ADT/StringRef.h:156:
char llvm::StringRef::back() const: Assertion `!empty()' failed.
Stack dump:
0.      Program arguments:
/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt -loop-rotate
-partial-inliner -strip -instcombine small.bc -o small-opt.bc 
1.      Running pass 'Function Pass Manager' on module 'small.bc'.
2.      Running pass 'Combine redundant instructions' on function '@0'
 #0 0x00005556a267d27a llvm::sys::PrintStackTrace(llvm::raw_ostream&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x277727a)
 #1 0x00005556a267af54 llvm::sys::RunSignalHandlers()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2774f54)
 #2 0x00005556a267b092 SignalHandler(int)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2775092)
 #3 0x00007f526f2da890 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
 #4 0x00007f526df8ce97 raise
/build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #5 0x00007f526df8e801 abort /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
 #6 0x00007f526df7e39a __assert_fail_base
/build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
 #7 0x00007f526df7e412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
 #8 0x00005556a2799899 optimizeDoubleFP(llvm::CallInst*,
llvm::IRBuilder<llvm::ConstantFolder, llvm::IRBuilderDefaultInserter>&, bool,
bool)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2893899)
 #9 0x00005556a279a391 llvm::LibCallSimplifier::optimizeSqrt(llvm::CallInst*,
llvm::IRBuilder<llvm::ConstantFolder, llvm::IRBuilderDefaultInserter>&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2894391)
#10 0x00005556a279e016
llvm::LibCallSimplifier::optimizeFloatingPointLibCall(llvm::CallInst*,
llvm::LibFunc, llvm::IRBuilder<llvm::ConstantFolder,
llvm::IRBuilderDefaultInserter>&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2898016)
#11 0x00005556a279f424 llvm::LibCallSimplifier::optimizeCall(llvm::CallInst*)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x2899424)
#12 0x00005556a219c8db llvm::InstCombiner::tryOptimizeCall(llvm::CallInst*)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x22968db)
#13 0x00005556a219f9fc llvm::InstCombiner::visitCallBase(llvm::CallBase&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x22999fc)
#14 0x00005556a21a049b llvm::InstCombiner::visitCallInst(llvm::CallInst&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x229a49b)
#15 0x00005556a2170c96 llvm::InstCombiner::run()
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x226ac96)
#16 0x00005556a21732da combineInstructionsOverFunction(llvm::Function&,
llvm::InstCombineWorklist&, llvm::AAResults*, llvm::AssumptionCache&,
llvm::TargetLibraryInfo&, llvm::DominatorTree&,
llvm::OptimizationRemarkEmitter&, llvm::BlockFrequencyInfo*,
llvm::ProfileSummaryInfo*, bool, llvm::LoopInfo*)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x226d2da)
#17 0x00005556a21738f1
llvm::InstructionCombiningPass::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x226d8f1)
#18 0x00005556a1fbcde9 llvm::FPPassManager::runOnFunction(llvm::Function&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6de9)
#19 0x00005556a1fbcee1 llvm::FPPassManager::runOnModule(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6ee1)
#20 0x00005556a1fbc041 llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x20b6041)
#21 0x00005556a079574f main
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x88f74f)
#22 0x00007f526df6fb97 __libc_start_main
/build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
#23 0x00005556a080d54a _start
(/home/jack-zhou/Documents/llvm/llvm_truck/llvm2/build9/bin/opt+0x90754a)
Aborted (core dumped)

------------------------------------------
#include<math.h>
float a;
int c;
void b() {
  for (; c;)
    sqrt(a);
}
int main() { b(); return 0;}</pre>
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