Proposal: @prefetch builtin

[data-man]

Accepted Proposal

---

LLVM docs

@llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>, i32 <cache type>)

Possible syntax:

pub const FetchType = enum {
    Read,
    Write
}

pub const CacheType = enum {
    Instruction,
    Data
}

pub const Locality = enum {
    No,
    ...,
    ...,
    Extremely
}

@prefetch(comptime fetchType: FetchType,
          comptime cacheType: CacheType,
          comptime locality: Locality,
          ptr: var) noreturn

Related: #767

[shawnl]

yeah I like it, except that isData should be a enum with .Data and .Instruction, and isWrite should also be an enum---these just mean that its easier to read the code.

[data-man]

Updated.

[andrewrk]

To go into std.builtin:

/// This data structure is used by the Zig language code generation and
/// therefore must be kept in sync with the compiler implementation.
pub const Prefetch = struct {
    rw: Rw = .read,
    /// 0 means no locality.
    /// 3 means extremely local, keep in cache.
    locality: u2 = 3,
    type: Type = .data,

    pub const Rw = enum { read, write };
    pub const Type = enum { instruction, data };
};

@prefetch(ptr: anytype, options: Prefetch) void

Any objections?

[andrewrk]

Landed in 97c0373 just in time for 0.9.0.