abi_ptx - The Rust Unstable Book

# `abi_ptx`

The tracking issue for this feature is: #38788

When emitting PTX code, all vanilla Rust functions (`fn`) get translated to "device" functions. These functions are not callable from the host via the CUDA API so a crate with only device functions is not too useful!

OTOH, "global" functions can be called by the host; you can think of them as the real public API of your crate. To produce a global function use the `"ptx-kernel"` ABI.

    #![feature(abi_ptx)]
    #![no_std]

    pub unsafe extern "ptx-kernel" fn global_function() {
        device_function();
    }

    pub fn device_function() {
        // ..
    }

    $ xargo rustc --target nvptx64-nvidia-cuda --release -- --emit=asm

    $ cat $(find -name '*.s')
    //
    // Generated by LLVM NVPTX Back-End
    //

    .version 3.2
    .target sm_20
    .address_size 64

            // .globl       _ZN6kernel15global_function17h46111ebe6516b382E

    .visible .entry _ZN6kernel15global_function17h46111ebe6516b382E()
    {

            ret;
    }

            // .globl       _ZN6kernel15device_function17hd6a0e4993bbf3f78E
    .visible .func _ZN6kernel15device_function17hd6a0e4993bbf3f78E()
    {

            ret;
    }