sparse-llvm initialization of local vars

sparse-llvm initialization of local vars

[Dibyendu Majumdar]

Hi,

I noticed that when local variables are initialized, only explicit
initialization instructions are output. But I think C requires that
the whole object be zeroed out as well.

Example code:

extern int printf(const char *s, ...);

struct foo {
long long int i,j;
};

static void dosomething(struct foo *foo)
{
printf("foo->i = %lld, foo->j = %lld\n", foo->i, foo->j);
}

int main(void)
{
struct foo foo = { 1, 2 };
struct foo bar = { 99 };
dosomething(&foo);
dosomething(&bar);
return 0;
}

In this example, sparse-llvm outputs garbage value for bar->j whereas
it should be 0.

To fix this, before any instructions for initialization is run,
sparse-llvm should zero out the whole object using LLVM intrinsic such
as memset. This is implemented in my repository.

Regards
Dibyendu