[SimplifyCFG] Optimize CFG when null is passed to a function with nonnull argument
Example:
__attribute__((nonnull,noinline)) char * pinc(char *p) {
return ++p;
}
char * foo(bool b, char *a) {
return pinc(b ? 0 : a);
}optimize to
char * foo(bool b, char *a) {
return pinc(a);
}Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D94180