clang -O3 -mllvm -disable-llvm-optzns -c -emit-llvm a.c -o a.bc
opt -passes=dse,newgvn a.bc -o a.opt.bc
clang a.opt.bc -o a.out
./a.out
4
opt a.bc -o a.opt.bc
clang a.opt.bc -o a.out
./a.out
-17

#include<stdio.h>
struct {
  int a;
} b;
short c;
unsigned int d() {
  int e[2][3][9] = {};
  unsigned char f;
  for (c = -17; c < 0; c = 4) {
    int g;
    for (; b.a >= 0;)
      for (f = 0;;) {
        int h;
        return e[f][f][0];
      }
  }
  return e[0][0][1];
}
int main() {
  d();
  printf("%d\n", c);
  return 0;
}