Context sensitive array bounds for all function calls

[Machiry]

We will create context-sensitive bounds key for inferring array bounds. Previously, we did this only for functions that have bounds declarations, but this pull-request extends this to all functions.

Consider the following code:

struct hash_node
{
  int *w_key;
  int *y_key;
  unsigned xo;
  unsigned lo;
};
void ctxsensfunc(int *p, unsigned n) {
    unsigned i;
    for (i=0; i<n; i++) {
	p[i] = 0;
    }
}

int foo() {
    unsigned j;
    struct hash_node *n
    ctxsensfunc(n->w_key, n->xo);
    j = n->lo;
    ctxsensfunc(n->y_key, j);
    return 0;
}

Here, for each of the call-sites of ctxsensfunc we create new BoundsKey and array length inference will correctly infer the length of the structure members as follows:

struct hash_node
{
  _Array_len<int> w_key : count(xo);
  _Array_len<int> y_key : count(lo);
  unsigned xo;
  unsigned lo;
};
void ctxsensfunc(_Array_len<int> p : count(n), unsigned n) {
    unsigned i;
    for (i=0; i<n; i++) {
	p[i] = 0;
    }
}

int foo() {
    unsigned j;
    struct hash_node *n
    ctxsensfunc(n->w_key, n->xo);
    j = n->lo;
    ctxsensfunc(n->y_key, j);
    return 0;
}

[john-h-kastner]

Could this instead return a const std::string & or llvm::StringRef to avoid copying the string?

[Machiry]

Agree. Done.

[Machiry]

@jackastner Do these changes look good to you?

[john-h-kastner]

Looks good