[Clang 20.1.0] Missed strlen when cmp to NUL forwards with increments

[BreadTom]

https://godbolt.org/z/adf71b63Y
f1() should optimized to f0(). f0() should call strlen just like GCC 14.2.
C code

#include <stddef.h>

size_t f0(char *str){
    size_t i = 0;
    for(; str[i] != '\0'; ++i){

    }
    return i;
}

size_t f1(char *str, size_t inc){
    if(inc < 2)
        __builtin_unreachable();
    if(str[0] == '\0')
        return 0;
    size_t i = 0;
    for(;; i += inc){
        for(size_t n = 0; n < inc; ++n){
            if(str[i+n] == '\0'){
                return i+n;
            }
        }
    }
    return i;
}

Bug also reported at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119431

[pinskia]

f0 should be fixed by #132572

[mustartt]

After relanding #132572

I can check to see what else is need to to support f1(). But that might have to come after some more strlen intrinsics related work. But once again, does this code show up often enough in the wild to be profitable in general?