[llvm-bugs] [Bug 41291] New: [licm] LICM cannot terminate

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41291

            Bug ID: 41291
           Summary: [licm] LICM cannot terminate
           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 21700
  --> https://bugs.llvm.org/attachment.cgi?id=21700&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

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

$opt -structurizecfg -reg2mem small.bc -o small-opt.bc

$opt -licm small-opt.bc
In this step, opt will consume too much memory and not terminate.
By using godbolt, it shows that the llvm 7/truck version also has this problem.

/compiler-explorer/c-preload/compiler-wrapper: line 21: 22186 Killed           
      "$@"

Compiler returned: 137

---------------------------------------
struct S0 {
  int f2;
  int f5;
  int e
};
struct f {};
union U4 {
  int f0;
};
a;
union U4 *b;
struct S0 g_1231;
g_1237;
struct S0 c;
struct S0 d;
func_1_i;
union U4 i() {
  int j;
  for (0; a; a)
    if (0) {
      int l_3671;
      for (; 0;) {
        for (; func_1_i; func_1_i) {
          struct S0 l_3685;
          for (; 0;) {
            int l_3678;
            if ((g(0, 0)))
              for (; 0; g_1237) {
                union U4 h;
                return h;
              }
          }
        }
      }
      union U4 *l_3860;
    lbl_4065:
      for (; 0;) {
        struct f l_4102;
        for (; 0;) {
          const l_3993;
          for (; 0;) {
            int l_4111;
            if ((j))
              for (; 0; g_1231)
                return (*l_3860);
          }
        }
        for (; 0;)
          for (d.f2; 0; d)
            for (0; 0; c.f5 -= 1) {
              return (*b);
            }
      }
    }
}
int main(int argc, char *argv[]) {}

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