How does _mm_prefetch work?

Question

The call _mm_prefetch, as indicated here , preloads the contents from the specified memory location into RAM into the cache line. But is the cache completely under hardware control? Based on which memory (based on spatial / temporal locations) is available for access, the hardware preloaded the contents from memory into the cache. I thought that programmers did not have control over the cache, and this is a completely hardware mechanism.

So, my understanding is wrong, and the cache can really be controlled by us, right?

If it _mm_prefetchcan control what can be cached,

• Does this mean that it will never be removed from the cache when?

• What is an equivalent assembly level instruction that works on cache mechanisms?

Answer 1

We can always move data to the cache if it is active simply by accessing memory.
We can pre-select var, simply by “touching” it ahead of time, for this we do not need special instructions.

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