more loop vectorization opportunities

Here are some loops that can be vectorized(compared with gcc) but not.
```
typedef unsigned char uint8;
typedef short int16;
typedef unsigned short uint16;
typedef unsigned int uint32;
typedef unsigned long uint64;
typedef long int64;

typedef struct {
  int v[20];
} Sv;

// bad deptest
void VecLoop1(int *v, int len) {
  for (int i = 0; i < len - 1; i++) {
    v[i] = v[i+1];
  }
}

// bad deptest
void VecLoop2(int *v, int len) {
  for (int i = 8; i < len; i++) {
    v[i] = v[i-8];
  }
}

// complex array index
void VecLoop3(int *v, int len, int16 c, Sv *sv) {
  for (int i = 0; i < len; i+=2) {
    *(uint16*)&v[i] = *(uint16*)&sv->v[i];
  }
}

// not a doloop
int VecLoop4(int len) {
  int v11[20];
  int v22[20];
  int *v1 = &v11[0];
  int *v2 = &v22[0];
  while (len-- > 0) {
    *v1++ = *v2++;
    *v1++ = *v2++;
    *v1++ = *v2++;
    *v1++ = *v2++;
  }
  return v1[15] + v2[5];
}

// not a doloop
void VecLoop5(int *v, uint64 len, int c) {
  for (uint32 i = 0; i < len; i++) {
    *v = c;
    v++;
  }
}
```

**new case** 
```
typedef unsigned char uint8;
typedef short int16;
typedef unsigned short uint16;
typedef unsigned int uint32;
typedef unsigned long uint64;
typedef long int64;

// some if/select can also do vectorization
int VecLoop6(int *v, int len) {
  int sum = 0;
  for (int i = 0; i < len; i++) {
    if (v[i] == -1) {
      sum++;
    }
  }
  return sum;
}

// support iv assign
void VecLoop7(int *v, int len) {
  for (int i = 0; i < len; i++) {
    v[i] = i;
  }
}

// support const subscript
void VecLoop8(int *__restrict v1, int *__restrict v2, int len) {
  for (int i = 0; i < len; i++) {
    v1[3] += v2[i];
  }
}

// support vec xor
void VecLoop9(int *v, int len) {
  for (int i = 0; i < len; i++) {
    v[i] = v[i] ^ 3;
  }
}

// more complicate cmp
int VecLoop10(int *v, int len, int a) {
  int sum = 0;
  for (int i = 0; i < len; i++) {
    if (a & (1 << (3 - i))) {
      sum += 3;
    }
  }
  return sum;
}

// not a doloop, more loop invariant analysis
char cond = 5;
int GetCond() {
  return (int)cond + 4;
}
int VecLoop11(int *v) {
  int sum = 0;
  for (int i = 0; i < GetCond(); i++) {
    sum += v[i];
  }
  return sum;
}
```

GVP 方舟编译器/OpenArkCompiler

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GVP方舟编译器/OpenArkCompiler

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