pto.ttrans

pto.ttrans is part of the Layout And Rearrangement instruction set.

Summary

Transpose with a temporary tile whose allocation and usage depend on the target. On A2/A3 the transpose is performed in-place using the scratchpad as staging; on A5 the operation requires an explicit tmp tile passed via the C++ API because the A5 DMA engine cannot perform a true in-place transpose and needs a scratch buffer of the same shape as the source. On the CPU simulator the tmp tile is not used but must still be provided.

Mechanism

Transpose with a temporary tile whose allocation and usage depend on the target. On A2/A3 the transpose is performed in-place using the scratchpad as staging; on A5 the operation requires an explicit tmp tile passed via the C++ API because the A5 DMA engine cannot perform a true in-place transpose and needs a scratch buffer of the same shape as the source. On the CPU simulator the tmp tile is not used but must still be provided. It belongs to the tile instructions and carries architecture-visible behavior that is not reducible to a plain elementwise compute pattern.

For a 2D tile, over the effective transpose domain:

\[ \mathrm{dst}_{i,j} = \mathrm{src}_{j,i} \]

Exact shape/layout and the transpose domain depend on the target (see Constraints).

Syntax

Textual spelling is defined by the PTO ISA syntax-and-operands pages.

Synchronous form:

%dst = ttrans %src : !pto.tile<...> -> !pto.tile<...>
Lowering may introduce internal scratch tiles; the C++ intrinsic requires an explicit tmp operand.

AS Level 1 (SSA)

%dst = pto.ttrans %src : !pto.tile<...> -> !pto.tile<...>

AS Level 2 (DPS)

pto.ttrans ins(%src : !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)

C++ Intrinsic

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

template <typename TileDataDst, typename TileDataSrc, typename TileDataTmp, typename... WaitEvents>
PTO_INST RecordEvent TTRANS(TileDataDst &dst, TileDataSrc &src, TileDataTmp &tmp, WaitEvents &... events);

Inputs

  • src is the source tile.
  • tmp is a temporary tile used during transpose (may not be used by all implementations).
  • dst names the destination tile. The operation iterates over dst's valid region.

Expected Outputs

dst holds the transposed version of src: dst[i,j] = src[j,i].

Side Effects

No architectural side effects beyond producing the destination tile. Does not implicitly fence unrelated traffic.

Constraints

Constraints

  • Temporary tile:

    • The C++ API requires tmp, but some implementations may not use it.

  • ConvTile:

    • Transpose of ConvTile for TileType::Vec is supported。 Element size must be 1、2 or 4 bytes. Supported element types are uint32_t、int32_t、float、uint16_t、int16_t、half、bfloat16_t、uint8_t、int8_t.
    • Format transformation from NCHW to NC1HWC0 is supported, while C1 == (C + C0 - 1)/C0，HW matches alignment constraint，which means H*W*sizeof(T)==0. C0 means c0_size, which C0 * sizeof(T) == 32。C0 can also be 4.
    • Format transformation from NC1HWC0 to FRACTAL_Z is supported， while N1 == (N + N0 - 1)/N0。N0 should be 16.

Exceptions

Exceptions

  • Illegal operand tuples, unsupported types, invalid layout combinations, or unsupported target-profile modes are rejected by the verifier or by the selected backend instruction set.
  • Programs must not rely on behavior outside the documented legal domain of this operation, even if one backend currently accepts it.

Target-Profile Restrictions

Target-Profile Restrictions

  • Implementation checks (A2A3):

    • sizeof(TileDataSrc::DType) == sizeof(TileDataDst::DType).
    • Source layout must be row-major (TileDataSrc::isRowMajor).
    • Element size must be 1, 2, or 4 bytes.
    • Supported element types are restricted per element width:
    • 4 bytes: uint32_t, int32_t, float
    • 2 bytes: uint16_t, int16_t, half, bfloat16_t
    • 1 byte: uint8_t, int8_t
    • The transpose size is taken from src.GetValidRow() / src.GetValidCol().

  • Implementation checks (A5):

    • sizeof(TileDataSrc::DType) == sizeof(TileDataDst::DType).
    • 32-byte alignment constraints are enforced on the major dimension of both input and output (row-major checks Cols * sizeof(T) % 32 == 0, col-major checks Rows * sizeof(T) % 32 == 0).
    • Supported element types are restricted per element width:
    • 4 bytes: uint32_t, int32_t, float
    • 2 bytes: uint16_t, int16_t, half, bfloat16_t
    • 1 byte: uint8_t, int8_t
    • The implementation operates over the static tile shape (TileDataSrc::Rows/Cols) and does not consult GetValidRow/GetValidCol.

Examples

Auto

#include <pto/pto-inst.hpp>

using namespace pto;

void example_auto() {
  using SrcT = Tile<TileType::Vec, float, 16, 16>;
  using DstT = Tile<TileType::Vec, float, 16, 16>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TTRANS(dst, src, tmp);
}

Manual

#include <pto/pto-inst.hpp>

using namespace pto;

void example_manual() {
  using SrcT = Tile<TileType::Vec, float, 16, 16>;
  using DstT = Tile<TileType::Vec, float, 16, 16>;
  using TmpT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src;
  DstT dst;
  TmpT tmp;
  TASSIGN(src, 0x1000);
  TASSIGN(dst, 0x2000);
  TASSIGN(tmp, 0x3000);
  TTRANS(dst, src, tmp);
}

Auto Mode

# Auto mode: compiler/runtime-managed placement and scheduling.
%dst = pto.ttrans %src : !pto.tile<...> -> !pto.tile<...>

Manual Mode

# Manual mode: bind resources explicitly before issuing the instruction.
# Optional for tile operands:
# pto.tassign %arg0, @tile(0x1000)
# pto.tassign %arg1, @tile(0x2000)
%dst = pto.ttrans %src : !pto.tile<...> -> !pto.tile<...>

PTO Assembly Form

%dst = ttrans %src : !pto.tile<...> -> !pto.tile<...>
# AS Level 2 (DPS)
pto.ttrans ins(%src : !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)