0.2.3: mcpp.rules.ascendc — Ascend C compiled by BiSheng, and no NPU required to do it

[Sunrisepeak]

The fifth rule, and the first written against a vendor this project had never
built for. Everything below was measured on CANN 8.5.0, on a machine with
no Ascend hardware.

The compile line

From the toolkit's own CMakeASCInformation.cmake:

bisheng <DEFINES> <INCLUDES> -fPIC <FLAGS> -o <OBJECT> -c -x asc <SOURCE>

and three things that file does not say, each found by running it:

• ASCEND_HOME_PATH must be in the environment, and points at the arch
  directory, not the toolkit root. Without it: PlugIn Err: can not find ASCEND_HOME_PATH, before the source is looked at.
• The plugin needs libmmpa.so on the loader path. Without it the plugin
  fails to load and the failure surfaces as unknown type name '__aicore__' —
  a message about the source that is not about the source.
• -DTILING_KEY_VAR=0 and eleven include directories, which is what the
  toolkit's device_intf_pub target carries.

Not --cce-aicore-only

With it, BiSheng emits a Da Vinci object (*unknown arch 0x1029*) the host
linker cannot place. Without it, the same source yields an x86-64 object
carrying both the device binary (registered at load time) and a host-callable
launcher per __global__ function — which is exactly what mcpp's model needs:
a device unit becomes an object and the ordinary link takes it. No registration
JSON, no device-link step.

The launcher is C++-mangled even when the kernel is extern "C", so the
rule tells a project to put an extern "C" wrapper in the same .asc file
rather than depend on two compilers agreeing about mangling.

The link closure, which no project could name

A mixed-mode object needs libascendc_runtime.a; that archive is static, so
its undefined symbols become the program's: libascend_dump, libruntime,
libmmpa, libprofapi, libc_sec. Then -Wl,-rpath-link for the library
directory and the toolkit's driver stubs — GNU ld resolves a shared
library's own DT_NEEDED through -rpath-link, never through -L, and
without it the link fails on memset_s and CheckLogLevel, symbols belonging
to libraries nobody named. Then -Wl,-rpath, because mcpp gives an artifact a
private interpreter and a program that links but cannot start is not progress.

That -rpath-link pair has no declarative spelling — it is what mcpp
2026.9.6.5's link_flag outlet exists for, and why this member's floor is that
release.

Verified end to end

mcpp's examples/09-heterogeneous/cann compiles its kernel with BiSheng, links
the object into an ordinary binary, and resolves every runtime dependency
except libascend_hal.so — the driver, absent on a machine with no NPU and
exactly what should be missing there. Its CPU leg builds and runs
(12 24 36 48).

No tests/ fixture

Same reason the index recipe gives: the toolkit is a 1.1 GB download the CI job
cannot carry, and a test that would never run is worse than none.