ocaml_intrinsics v0.17.0 (latest)

Bring the line of data from memory that contains the specified address.

The instruction is a hint that is ignored on some targets. Some values or temporal_locality and operation hints are not supported on some targets.

type temporal_locality =

| None
| Low
| Moderate
| High

temporal locality is a hint to a location in the cache hierarchy where the prefetch data should be placed.

Higher temporal locality hint means prefetching data closer to the CPU. For example, on Intel targets, High means prefetch to all levels of cache, and Moderate means prefetch to L2 cache and higher, but not L1 cache.

type operation =

| Read
| Write

Anticipated operation that the data will used for. In preparation for write, the data can be brought into cache in exclusive state, whereas for read, shared state is sufficient.

val value : 
  'a ->
  operation:operation ->
  temporal_locality:temporal_locality ->
  unit

value a prefetches the OCaml value a. It should not be used when a is an immediate: it is safe, but will attempt to prefetch an arbitrary memory address.

val value_pos : 
  'a ->
  pos:int ->
  operation:operation ->
  temporal_locality:temporal_locality ->
  unit

value a ~pos prefetches record field, tuple or array element at position pos, starting from 0. For records, field positions are determined by the order of fields in the type definition. See also value_byte_offset.

It should not be used when a is an immediate: it is safe, but will attempt to prefetch an arbitrary memory address. Similarly, there are no bounds checks on pos.

val value_byte_offset : 
  'a ->
  byte_offset:int ->
  operation:operation ->
  temporal_locality:temporal_locality ->
  unit

value a ~byte_offset prefetches memory at byte_offset from address of OCaml value a.

It should not be used when a is an immediate: it is safe, but will attempt to prefetch an arbitrary memory address. Similarly, there are no bounds checks on byte_offset.

The difference between value_pos and value_byte_offset:

value_pos calculates the byte offset given pos and the target size, which works well for most types.

value_byte_offset expects the caller to calculate the byte offset. It should be used for String.t,Bytes.t, float arrays, and (in the future) unboxed types.

val native_pointer : 
  Native_pointer.t ->
  operation:operation ->
  temporal_locality:temporal_locality ->
  unit

val ext_pointer : 
  Ext_pointer.t ->
  operation:operation ->
  temporal_locality:temporal_locality ->
  unit

val bigstring : 
  Bigstring_intf.t ->
  pos:int ->
  operation:operation ->
  temporal_locality:temporal_locality ->
  unit

val pause : unit -> unit

Processor hint that improves performance of spin-wait loops.

module Expert = Prefetch_expert

The prefetch functions above rely on inlining heuristics to eliminate selection logic and emit a single call to an external function. It usually works well with Flambda, but might not be reliable in other contexts. Expert module exposes the underlying external declarations for all prefetch intrinsics.

package ocaml_intrinsics