By defining this temp variable we use that fact that `i` is never
equal to `Li[j]`. Compiler does not have this information.

binary code for the loop changes from
```
        movsx   rdi, DWORD PTR [rdx+rax*4]
        vmovss  xmm0, DWORD PTR [rcx+rax*4]
        add     rax, 1
        lea     rdi, [r8+rdi*4]
        vmovss  xmm1, DWORD PTR [rdi]
        vfnmadd132ss    xmm0, xmm1, DWORD PTR [r9]
        vmovss  DWORD PTR [rdi], xmm0
```

to

```
        movsx   rdi, DWORD PTR [rdx+rax*4]
        vmovss  xmm0, DWORD PTR [rcx+rax*4]
        add     rax, 1
        lea     rdi, [r8+rdi*4]
        vfnmadd213ss    xmm0, xmm1, DWORD PTR [rdi]
        vmovss  DWORD PTR [rdi], xmm0
```

notice the drop of the first `vmovss` by the compiler.