[llvm-bugs] [Bug 41289] New: slp-vectorizer cannot terminate

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41289

            Bug ID: 41289
           Summary: slp-vectorizer 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 21696
  --> https://bugs.llvm.org/attachment.cgi?id=21696&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 -gvn -structurizecfg  small.bc -o small-opt.bc

$opt -slp-vectorizer  small-opt.bc
In this step, opt will consume too much memory and not terminate.

By using godbolt, it shows that the llvm 6/7/truck version also has this
problem.

-----------------------------------------
struct {
  int a;
  int b;
  int c
} * d, e, f, g, h;
fn1() {
  int j;
  int k;
  int l;
  int m;
n : {
  int o;
p:
  if (j)
    for (; e.a;) {
      int q;
      for (; h.c;) {
        int i;
        if (k)
          goto p;
        if (l)
          for (; 2; i)
            return o;
      }
    }
  int r;
  if (m)
  aa:
    if (0 & r && 0)
      for (; 0;) {
        int a;
        for (; 0;) {
          if (a)
            goto n;
          for (; f.c; f)
            goto aa;
        }
        for (; 0;)
          for (; g.b; 1)
            return d;
      }
}
}

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