TGATHER

Tile Operation Diagram

Introduction

Gather/select elements using either an index tile or a compile-time mask pattern.

Math Interpretation

Index-based gather (conceptual):

Let R = dst.GetValidRow() and C = dst.GetValidCol(). For 0 <= i < R and 0 <= j < C:

$${\mathrm{d}\mathrm{s}\mathrm{t}}_{i,j}=\mathrm{s}\mathrm{r}\mathrm{c}0\left[{\mathrm{i}\mathrm{n}\mathrm{d}\mathrm{i}\mathrm{c}\mathrm{e}\mathrm{s}}_{i,j}\right]$$

Exact index interpretation and bounds behavior are implementation-defined.

Mask-pattern gather is an implementation-defined selection/reduction controlled by pto::MaskPattern.

Assembly Syntax

PTO-AS form: see PTO-AS Specification.

Index-based gather:

%dst = tgather %src0, %indices : !pto.tile<...> -> !pto.tile<...>

Mask-pattern gather:

%dst = tgather %src {maskPattern = #pto.mask_pattern<P0101>} : !pto.tile<...> -> !pto.tile<...>

AS Level 1 (SSA)

%dst = pto.tgather %src, %indices : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>
%dst = pto.tgather %src {maskPattern = #pto.mask_pattern<P0101>}: !pto.tile<...> -> !pto.tile<...>

AS Level 2 (DPS)

pto.tgather ins(%src, %indices : !pto.tile_buf<...>, !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)
pto.tgather ins(%src, {maskPattern = #pto.mask_pattern<P0101>} : !pto.tile_buf<...>) outs(%dst : !pto.tile_buf<...>)

C++ Intrinsic

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

template <typename TileDataD, typename TileDataS0, typename TileDataS1, typename TileDataTmp, typename... WaitEvents>
PTO_INST RecordEvent TGATHER(TileDataD &dst, TileDataS0 &src0, TileDataS1 &src1, TileDataTmp &tmp, WaitEvents &... events);

template <typename DstTileData, typename SrcTileData, MaskPattern maskPattern, typename... WaitEvents>
PTO_INST RecordEvent TGATHER(DstTileData &dst, SrcTileData &src, WaitEvents &... events);

Constraints

• Index-based gather: implementation checks (A2A3):
  • sizeof(DstTileData::DType) must be must be int16_t, uint16_t, int32_t, uint32_t, half, float.
  • sizeof(Src1TileData::DType) must be must be int32_t, uint32_t.
  • DstTileData::DType must be the same type as Src0TileData::DType.
  • src1.GetValidCol() == Src1TileData::Cols and dst.GetValidCol() == DstTileData::Cols.
• Index-based gather: implementation checks (A5):
  • sizeof(DstTileData::DType) must be must be int16_t, uint16_t, int32_t, uint32_t, half, float.
  • sizeof(Src1TileData::DType) must be must be int16_t, uint16_t, int32_t, uint32_t.
  • DstTileData::DType must be the same type as Src0TileData::DType.
  • src1.GetValidCol() == Src1TileData::Cols and dst.GetValidCol() == DstTileData::Cols.
• Mask-pattern gather: implementation checks (A2A3):
  • Source element size must be 2 or 4 bytes.
  • SrcTileData::DType/DstTileData::DType must be int16_t or uint16_t or int32_t or uint32_t or half or bfloat16_t or float.
  • dst and src must both be TileType::Vec and row-major.
  • sizeof(dst element) == sizeof(src element) and dst.GetValidCol() == DstTileData::Cols (continuous dst storage).
• Mask-pattern gather: implementation checks (A5):
  • Source element size must be 1 or 2 or 4 bytes.
  • dst and src must both be TileType::Vec and row-major.
  • SrcTileData::DType/DstTileData::DType must be int8_t or uint8_t or int16_t or uint16_t or int32_t or uint32_t or half or bfloat16_t or float or float8_e4m3_tor float8_e5m2_t or hifloat8_t.
  • Supported dtypes are restricted to a target-defined set (checked via static_assert in the implementation), and sizeof(dst element) == sizeof(src element), dst.GetValidCol() == DstTileData::Cols (continuous dst storage).
• Bounds / validity:
  • Index bounds are not validated by explicit runtime assertions; out-of-range indices are target-defined.

Examples

Auto

#include <pto/pto-inst.hpp>

using namespace pto;

void example_auto() {
  using SrcT = Tile<TileType::Vec, float, 16, 16>;
  using IdxT = Tile<TileType::Vec, int32_t, 16, 16>;
  using DstT = Tile<TileType::Vec, float, 16, 16>;
  SrcT src0;
  IdxT idx;
  DstT dst;
  TGATHER(dst, src0, idx);
}

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, 1, 16>;
  SrcT src;
  DstT dst;
  TASSIGN(src, 0x1000);
  TASSIGN(dst, 0x2000);
  TGATHER<DstT, SrcT, MaskPattern::P0101>(dst, src);
}

ASM Form Examples

Auto Mode

# Auto mode: compiler/runtime-managed placement and scheduling.
%dst = pto.tgather %src, %indices : (!pto.tile<...>, !pto.tile<...>) -> !pto.tile<...>

Manual Mode

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

PTO Assembly Form

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