FNV1aSpan64(std::span<unsigned char, 18446744073709551615ul>): # @FNV1aSpan64(std::span<unsigned char, 18446744073709551615ul>)
        movabs  rdx, -3750763034362895579
        test    rsi, rsi
        je      .LBB0_1
        mov     r8d, esi
        movabs  rcx, 1099511628211
        lea     rax, [rsi - 1]
        and     r8d, 7
        cmp     rax, 7
        jb      .LBB0_5
        and     rsi, -8
.LBB0_4:                                # =>This Inner Loop Header: Depth=1
        movzx   eax, byte ptr [rdi]
        xor     rax, rdx
        movzx   edx, byte ptr [rdi + 1]
        imul    rax, rcx
        xor     rdx, rax
        movzx   eax, byte ptr [rdi + 2]
        imul    rdx, rcx
        xor     rax, rdx
        movzx   edx, byte ptr [rdi + 3]
        imul    rax, rcx
        xor     rdx, rax
        movzx   eax, byte ptr [rdi + 4]
        imul    rdx, rcx
        xor     rax, rdx
        movzx   edx, byte ptr [rdi + 5]
        imul    rax, rcx
        xor     rdx, rax
        movzx   eax, byte ptr [rdi + 6]
        imul    rdx, rcx
        xor     rax, rdx
        movzx   edx, byte ptr [rdi + 7]
        add     rdi, 8
        imul    rax, rcx
        xor     rdx, rax
        imul    rdx, rcx
        add     rsi, -8
        jne     .LBB0_4
.LBB0_5:
        mov     rax, rdx
        test    r8, r8
        je      .LBB0_8
        xor     esi, esi
.LBB0_7:                                # =>This Inner Loop Header: Depth=1
        movzx   eax, byte ptr [rdi + rsi]
        inc     rsi
        xor     rax, rdx
        imul    rax, rcx
        mov     rdx, rax
        cmp     r8, rsi
        jne     .LBB0_7
.LBB0_8:
        ret
.LBB0_1:
        mov     rax, rdx
        ret