[llvm-bugs] [Bug 47344] New: ICE on x86_64-linux-gnu at `-O3` (Instruction Combining seems stuck in an infinite loop after 100 iterations.)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47344

            Bug ID: 47344
           Summary: ICE on x86_64-linux-gnu at `-O3` (Instruction
                    Combining seems stuck in an infinite loop after 100
                    iterations.)
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: cnsun at uwaterloo.ca
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

$ clang-trunk -w t.c -O3
fatal error: error in backend: Instruction Combining seems stuck in an infinite
loop after 100 iterations.
clang-12: error: clang frontend command failed with exit code 70 (use -v to see
invocation)
clang version 12.0.0 (https://github.com/llvm/llvm-project.git
5feca7c9c336ed70c57e44a43f2677498480a56f)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/cnsun/usr/bin
clang-12: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-12: note: diagnostic msg: /tmp/t-766683.c
clang-12: note: diagnostic msg: /tmp/t-766683.sh
clang-12: note: diagnostic msg: 

********************
$ 
$ cat t.c
int a, b, c, e, f;
unsigned short d;
int main() {
  while (f) {
    int h;
    b = 0;
    for (; b <= 29; b++)
      if (e >= (e && (h = c)))
        d = (a = d) >> c;
    h;
  }
}
$ 
$ clang-trunk -v
clang version 12.0.0 (https://github.com/llvm/llvm-project.git
5feca7c9c336ed70c57e44a43f2677498480a56f)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/cnsun/usr/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$

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