Extended Description

$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;
}
}
}