TALLOC¶

Introduction¶

Allocate a producer FIFO slot from a TPipe and expose it as a GlobalTensor view.

TALLOC is used by the GlobalData split interface. It lets the producer get the current FIFO slot address, write data into that slot with normal memory instructions such as TSTORE, and then commit the slot with TPUSH(Pipe&, GlobalData&).

Operation Semantics¶

TALLOC performs three steps:

1. Wait for FIFO free space when pipe.prod.getAllocateStatus() and Pipe::shouldWaitFree(pipe.prod.tileIndex) are both true.
2. Compute the current FIFO slot address from pipe.prod.tileIndex.
3. Assign gmTensor to the FIFO slot address and increment the producer tile index.

TALLOC does not write any data and does not notify the consumer. The producer must write the slot contents before calling TPUSH(Pipe&, GlobalData&).

C++ Intrinsic¶

Declared in include/pto/common/pto_instr.hpp:

template <typename Pipe, typename GlobalData, TileSplitAxis Split,
          std::enable_if_t<is_global_data_v<GlobalData>, int> = 0, typename... WaitEvents>
PTO_INST RecordEvent TALLOC(Pipe &pipe, GlobalData &gmTensor, WaitEvents &... events);

Pipe is typically an A2A3 TPipe declared in include/pto/npu/a2a3/TPush.hpp:

template <uint8_t FlagID, uint8_t DirType, uint32_t SlotSize, uint32_t SlotNum,
          uint32_t LocalSlotNum = 2, bool IsNoSplit = false, bool EN_UNIT_FLAG = false>
struct TPipe;

Constraints¶

• A2A3 GlobalData producer:
  • GlobalData must satisfy is_global_data_v<GlobalData>.
  • Direction::DIR_C2V: the producer sees the whole FIFO slot.
  • Direction::DIR_V2C: split offsets may be applied for vector subblocks according to Split.
• FIFO slot:
  • SlotSize must be large enough for one logical FIFO entry.
  • SlotNum >= 1.
  • Pipe::SyncPeriod is derived from SlotNum: (SlotNum <= 2) ? SlotNum : SlotNum / 2.
• Split behavior:
  • TileSplitAxis::TILE_NO_SPLIT: no sub-vector offset is applied.
  • TileSplitAxis::TILE_UP_DOWN: vector subblocks map to row halves.
  • TileSplitAxis::TILE_LEFT_RIGHT: vector subblocks map to column halves.
• Synchronization:
  • Free-space waits are sparse and controlled by Pipe::SyncPeriod.
  • TALLOC does not record data-ready; use TPUSH(Pipe&, GlobalData&) after writing the slot.

Examples¶

Allocate, Store, Commit¶

#include <pto/pto-inst.hpp>

using namespace pto;

template <typename T>
AICORE void example_talloc(__gm__ void *fifoMem)
{
    constexpr uint32_t M = 128;
    constexpr uint32_t N = 128;
    constexpr uint32_t FlagID = 0;
    constexpr uint32_t FifoDepth = 2;

    using Pipe = TPipe<FlagID, Direction::DIR_C2V, M * N * sizeof(T), FifoDepth>;
    using SlotGlobal = GlobalTensor<T, Shape<1, 1, 1, M, N>, Stride<1, 1, 1, N, 1>>;
    using VecTile = Tile<TileType::Vec, T, M, N, BLayout::RowMajor, M, N>;

    Pipe pipe(fifoMem, 0x0, 0x0);
    SlotGlobal slot;
    VecTile tile;
    TASSIGN(tile, 0x0);

    TALLOC<Pipe, SlotGlobal, TileSplitAxis::TILE_NO_SPLIT>(pipe, slot);
    TSTORE(slot, tile);
    TPUSH<Pipe, SlotGlobal, TileSplitAxis::TILE_NO_SPLIT>(pipe, slot);
}

V2C Split Allocation¶

#include <pto/pto-inst.hpp>

using namespace pto;

template <typename T>
AICORE void example_v2c_split(__gm__ void *fifoMem)
{
    constexpr uint32_t M = 64;
    constexpr uint32_t N = 128;
    constexpr uint32_t FullM = M * 2;
    constexpr uint32_t FlagID = 0;
    constexpr uint32_t FifoDepth = 2;

    using Pipe = TPipe<FlagID, Direction::DIR_V2C, FullM * N * sizeof(T), FifoDepth>;
    using SlotGlobal = GlobalTensor<T, Shape<1, 1, 1, M, N>, Stride<1, 1, 1, N, 1>>;
    using VecTile = Tile<TileType::Vec, T, M, N, BLayout::RowMajor, M, N>;

    Pipe pipe(fifoMem, 0x0, 0x0);
    SlotGlobal slot;
    VecTile tile;
    TASSIGN(tile, 0x0);

    TALLOC<Pipe, SlotGlobal, TileSplitAxis::TILE_UP_DOWN>(pipe, slot);
    TSTORE(slot, tile);
    TPUSH<Pipe, SlotGlobal, TileSplitAxis::TILE_UP_DOWN>(pipe, slot);
}

ASM Form Examples¶

The current public assembly reference does not define a stable PTO-AS spelling for TALLOC. Use the C++ intrinsic form for manual CV FIFO programming.