[llvm-bugs] [Bug 41510] New: jump-threading makes the program suspend

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41510

            Bug ID: 41510
           Summary: jump-threading makes the program suspend
           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 21781
  --> https://bugs.llvm.org/attachment.cgi?id=21781&action=edit
.bc file of the source code

$clang -v
clang version 9.0.0 (trunk 355281)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm/build4/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/7.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

For the following code small.c, after running jump-threading pass, it will
suspend.
-----------------------------------------------------------
#include <stdio.h>
int a, b;
int main() {

c:
  for (; a <= 1; a++) {
    int d;
    if (d)
      goto c;
  }
  printf("%d\n",a);
}
-----------------------------------------------------------
$clang small.c -o small1.out && ./small1.out
2
$gcc small.c -o small2.out && ./small2.out
2

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

$opt -mem2reg small.bc -o small-opt1.bc

$clang small-opt1.bc -o small3.out && timeout -s 9 120 ./small3.out
2

$opt -jump-threading small-opt1.bc -o small-opt2.bc

$clang small-opt2.bc -o small4.out && time -s 9 120 ./small4.out
Killed

The program cannot terminate even for a long time.

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