[AIR] getRefeedCount: explicit per-emission override wins for any value

[erwei-xilinx]

Summary

• air.refeed_count on a channel put/get is lowered to AIE lock acquire/release values (and the write-lock init). air::getRefeedCount(ChannelInterface) previously honored a per-emission override only when its value was > 1, falling through to the channel-level declaration otherwise.
• This meant an explicit per-emission value of 1 could not locally disable a shared channel's re-feed default. It also meant a producer had no way to express a count-free re-broadcast as value-1 per emission — so a refeed_count beyond the target's max lock value (AIE-ML locks are 7-bit, max +63) would lower to an unsatisfiable AcquireGreaterEqual and deadlock, with no local escape hatch.
• Fix: an explicit per-emission air.refeed_count now wins for any value; only when the put/get carries no explicit attribute do we fall back to the channel declaration. The override is gated on an IntegerAttr so a malformed/wrong-typed attribute falls through to the channel declaration rather than silently disabling the re-feed.

Scope / what this does NOT do

• This makes the per-emission value authoritative and gives a producer a local escape hatch (express the re-broadcast as value-1 per emission to keep every lock value in range). It does not add hardware-lock-max validation: a refeed_count in [64, INT32_MAX] still verifies and would still exceed a 7-bit lock. Bounding the count to the target's actual max lock value (or falling back to a multi-buffer scheme) is left as follow-up.

Validation

• air.refeed_count was validated ([1, INT32_MAX], integer type) only on the channel declaration. Now that a per-emission value is authoritative, the same check is applied to the put/get carrier: the range/type check is extracted into verifyRefeedCountAttr and shared by the ChannelOp, ChannelPutOp, and ChannelGetOp verifiers. A malformed per-op value now errors at verification instead of being silently normalized to 1 in the reader.

Compatibility

Behavior change is limited to ops that explicitly set air.refeed_count == 1: they now return 1 instead of the channel-level default. Ops with no explicit attribute, or an explicit value > 1, are unchanged. No pass emits an explicit per-op value of 1, so auto-generated IR is unaffected.

Test plan

• ninja check-air-mlir — AIR dialect + AIRToAIE suites pass (141/141 locally).
• A put/get with explicit air.refeed_count = 1 on a channel whose declaration sets a higher default lowers to value-1 locks (override honored), not the channel default — folded into air_channel_producer_refeed.mlir with the file's triple CHECK-NOT idiom (init / AcquireGreaterEqual / Release) on a unique count.
• Per-op invalid-IR cases (put zero / huge / non-integer, get negative) rejected by the new put/get verifier, plus a valid value-1 override — added to air_channel_invalid.mlir.

[Copilot]

Pull request overview

Updates AIR’s getRefeedCount(ChannelInterface) resolution so that an explicit per-emission air.refeed_count attribute on a channel.put/get takes precedence for any value (including 1), instead of only when > 1. This supports locally disabling a shared channel’s refeed default during lowering to AIE locks.

Changes:

• Change override detection from “returned count > 1” to “attribute is explicitly present on the emission op”.
• Keep channel-declaration fallback only when the emission carries no explicit air.refeed_count.

Comments suppressed due to low confidence (1)

mlir/lib/Util/Util.cpp:714

• Using hasAttr() treats any presence of air.refeed_count (including the wrong attribute type) as an explicit override and forces the result to 1 via getRefeedCount(Operation*)'s fallback. Previously a malformed/non-integer per-emission attribute would fall through to the channel declaration; with this change it can silently disable a channel-level refeed default. Consider requiring an IntegerAttr here (and warning/falling back to the channel decl if the attribute exists but is not an integer).

  if (op.getOperation()->hasAttr(air::attrs::RefeedCount))
    return getRefeedCount(op.getOperation());
  return getRefeedCount(getChannelDeclarationThroughSymbol(op).getOperation());

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.