<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/68585>68585</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang crash(Segmentation fault) at -O2/3 (13 Regression)
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          jun-wei-zeng
      </td>
    </tr>
</table>

<pre>
    Clang at -O2/3 crashes.

When I compiled this code with different optimization levels on different versions of clang, I found that `-O2` caused ICE starting from `clang-13.0.0`, while `-O3` caused ICE starting from `clang-15.0.0`.

Compiler explorer: https://godbolt.org/z/s9rWe464P

```c
$ cat test.c
int a[];
int b, c, d, g;
long e;
void h() {
  b = 5 ^ b & b >> 8 & 15;
  b = 8 ^ a[b];
  b = 8 ^ a[b & 15];
}
void i() {
  int f[][5] = {1, 5, 5, 5, 10, 10, 5};
  for (; e;) {
    h();
    g = 4;
    for (; g; g--)
      if (f[g][g])
        ;
      else
 for (;;)
          ;
    c = 0;
    for (; c <= 7; c++) {
 d = 7;
      for (; d >= 2; d--)
        for (int k = 0; k < 6; k++)
          for (int j = 0; j < 7; j++)
            h();
 }
  }
}
$
$ clang-16 -O2 test.c
test.c:1:5: warning: tentative array definition assumed to have one element
int a[];
    ^
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /home/jwzeng/compilers/llvm/llvm-16.0.0/bin/clang-16 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name test.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -fcoverage-compilation-dir=/home/jwzeng/workplace/compiler_testing/scripts/testing-20231008-100t8csmith-v3-ubuntu/result/crash-S_1113912547/reduce1 -resource-dir /home/jwzeng/compilers/llvm/llvm-16.0.0/lib/clang/16 -I /home/jwzeng/tools/csmith/include -internal-isystem /home/jwzeng/compilers/llvm/llvm-16.0.0/lib/clang/16/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/home/jwzeng/workplace/compiler_testing/scripts/testing-20231008-100t8csmith-v3-ubuntu/result/crash-S_1113912547/reduce1 -ferror-limit 19 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/test-ced2bc.o -x c test.c
1.      <eof> parser at end of file
2.      Optimizer
  #0 0x0000561623103b68 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/jwzeng/compilers/llvm/llvm-16.0.0/bin/clang-16+0x3103b68)
  #1 0x0000561623101aae llvm::sys::RunSignalHandlers() (/home/jwzeng/compilers/llvm/llvm-16.0.0/bin/clang-16+0x3101aae)
  #2 0x00005616231041ed SignalHandler(int) Signals.cpp:0:0
  #3 0x00007f74165fb520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
  #4 0x00005616225eb1f1 computeKnownBitsFromOperator(llvm::Operator const*, llvm::APInt const&, llvm::KnownBits&, unsigned int, (anonymous namespace)::Query const&) ValueTracking.cpp:0:0
  #5 0x00005616225d9de5 computeKnownBits(llvm::Value const*, llvm::APInt const&, llvm::KnownBits&, unsigned int, (anonymous namespace)::Query const&) ValueTracking.cpp:0:0
 #6 0x00005616225f3cd3 computeKnownBitsFromShiftOperator(llvm::Operator const*, llvm::APInt const&, llvm::KnownBits&, llvm::KnownBits&, unsigned int, (anonymous namespace)::Query const&, llvm::function_ref<llvm::KnownBits (llvm::KnownBits const&, llvm::KnownBits const&)>) ValueTracking.cpp:0:0
 #7 0x00005616225eb67c computeKnownBitsFromOperator(llvm::Operator const*, llvm::APInt const&, llvm::KnownBits&, unsigned int, (anonymous namespace)::Query const&) ValueTracking.cpp:0:0
  #8 0x00005616225d9de5 computeKnownBits(llvm::Value const*, llvm::APInt const&, llvm::KnownBits&, unsigned int, (anonymous namespace)::Query const&) ValueTracking.cpp:0:0
 #9 0x00005616225ebe2e computeKnownBitsFromOperator(llvm::Operator const*, llvm::APInt const&, llvm::KnownBits&, unsigned int, (anonymous namespace)::Query const&) ValueTracking.cpp:0:0
  ...
  ...
 ...
  #255 0x000056162258bfbc llvm::ScalarEvolution::getSCEVAtScope(llvm::SCEV const*, llvm::Loop const*) (/home/jwzeng/compilers/llvm/llvm-16.0.0/bin/clang-16+0x258bfbc)
clang-16: error: unable to execute command: Segmentation fault (core dumped)
clang-16: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 16.0.0
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jwzeng/compilers/llvm/llvm-16.0.0/bin
clang-16: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-16: note: diagnostic msg: /tmp/test-321019.c
clang-16: note: diagnostic msg: /tmp/test-321019.sh
clang-16: note: diagnostic msg: 

********************
```

</pre>
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