Vx

E6020

Error · Topology/Hardware

E6020 — raw::async_copy in a lowering for an edge no declared topology equips with a copy engine. The capability lives in the machine file (transfer A -> B copy_engine); using an absent primitive is a compile error, not a fallback.

What the compiler reports

E6020
copy_engine

The fragments the test suite holds the compiler to. An ellipsis marks text the test does not constrain; the emitted message also carries a source location.

A program that triggers it

// Capability, not choice: no declared topology edge carries `copy_engine`,
// so raw::async_copy has no hardware to run on and is refused.
Topology Dev {
  memory: Memory::L2,
  visible: [Memory::L2, Memory::SMEM],
  transfer Memory::CPU_DRAM -> Memory::L2 : 10 GB/s,
  transfer Memory::L2 -> Memory::SMEM
}
impl Transfer<Memory::L2, Memory::SMEM> for Topology::Dev {
  fn move_tile(src: &Tensor<f32, [4]>, dst: &mut Tensor<f32, [4]>) -> i32 {
    raw::async_copy(dst, src, 0);
    raw::async_wait();
    raw::barrier();
    return 0;
  }
}
fn main() -> i32 {
  return 0;
}

From tests/middle_end/fail/raw_async_no_engine.vx, which asserts this diagnostic on every commit.

Related

Topologies and memoryThe chapter covering the rule this code enforces. All diagnosticsEvery code the compiler can emit, grouped by stage. E6019raw::barrier() anywhere but a top-level statement of the lowering body. The barrier's contract requires every lane to reach it; under a conditional or a loop that cannot be guaranteed syntactically, so it is rejected outright (conservative by design — restructure the body so the barrier is unconditional). E6021A violation of the async/synchronization discipline in a lowering body: a destination read while an async_copy into it is still outstanding, a body that ends with copies no async_wait covers, or a lowering for a synchronizing edge whose body does not end with raw::barrier() (the seam obligation of hir/seam.rs: a relaxed publication makes a stale read reachable).