3.4.163.1 Defaults:

If -xprefetch is not specified, -xprefetch=no%auto,explicit is assumed.

If only -xprefetch is specified, -xprefetch=auto,explicit is assumed.

The default of no%auto is assumed unless explicitly overridden with the use of -xprefetch without any arguments or with an argument of auto or yes. For example, -xprefetch=explicit is the same as -xprefetch=explicit,no%auto.

The default of explicit is assumed unless explicitly overridden with an argument of no%explicit or an argument of no. For example, -xprefetch=auto is the same as -xprefetch=auto,explicit.

If automatic prefetching is enabled, such as with -xprefetch or -xprefetch=yes, but a latency factor is not specified, then -xprefetch=latx:1.0 is assumed.