E6027

Error · Topology/Hardware

E6027 — A working set that overflows a space only across call boundaries: the peak along some call path — what each caller still holds when it calls, plus the deepest callee's own peak — exceeds the space's declared capacity, while every function on the path fits by itself (that case is E6010's). Computed by folding per-function capacity summaries over the call graph, after the per-function checks. Downgraded to W1028 when the space is declared overcommit.

What the compiler reports

E6027 … call path 'main -> stage$i32' … peaks at 6291456 bytes, over its 4194304 byte capacity

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

//
// Part of the Vx Project, under the Apache License v2.0 with LLVM Exceptions.
// See LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// The cross-call fold runs over the *monomorphized* call graph: the call site
// names the template, the summary belongs to the instance, and the path in
// the refusal names the instance. Same shape as the direct-call case -- the
// caller holds its tile across the call, the callee places its own, and only
// their sum overflows.
//

Memory CPU_DRAM {}
Memory W {
  within: Memory::CPU_DRAM, capacity: 4 MiB, managed: explicit
}
Topology Dev {
  arch: nvptx64,
  memory: Memory::W,
  visible: [Memory::W],
  transfer Memory::CPU_DRAM -> Memory::W : 10
  transfer Memory::W -> Memory::CPU_DRAM : 10
}

fn stage<T>(_t: T) -> i32 {
  let y = Tensor<f32, [1024, 768]>::uninit();
  let _sy = transfer(y, Memory::W);
  return 1;
}

fn main() -> i32 {
  let x = Tensor<f32, [1024, 768]>::uninit();
  let sx = transfer(x, Memory::W);
  let r = stage(7);
  let _back = transfer(sx, Memory::CPU_DRAM);
  return r;
}

From tests/frontend/fail/generic_callee_joins_the_working_set.vx, which asserts this diagnostic on every commit.

Topologies and memoryThe chapter covering the rule this code enforces. All diagnosticsEvery code the compiler can emit, grouped by stage. E6026A tensor whose element type the target hardware cannot represent, placed on it anyway. The machine model states what a device has (dtypes: [f32, f16, ...]); this is the check that a placement stays inside it. An H100 has no fp4, so an fp4 tensor placed on one asks for silicon that is not there — and the placement is in the type, so the question is answerable here rather than at a kernel launch on the machine that lacks the type. Only fires against a topology that declares dtypes:. An undeclared machine constrains nothing, which is what keeps every machine file written before the field kept working. E6028A recursive cycle that places tiles in a space with a declared capacity. The recursion depth is not known at compile time, so the true peak is unbounded and the placement is refused conservatively. Downgraded to W1028 when the space is declared overcommit.

E6027

What the compiler reports

A program that triggers it

Related