PTO-TILE-MODEL-SHAPE-ROWS-COLUMNS

1// PTO-UNIT: {"id":"PTO-TILE-MODEL-SHAPE-ROWS-COLUMNS","surface":"tile","classification":["model","shape","rows-columns"],"depends_on":["PTO-TILE-MODEL-STATE-DESCRIPTORS"]}2// Architectural Tile dimensions use exact powers of two. This bounded form3// covers every 16-bit dimension value without relying on implementation4// integer bitwise operators.5pure func IsNonzeroPowerOfTwo(value: integer {0..65535}) => boolean6begin7    if value == 0 then return FALSE; end;8    var candidate: integer = 1;9    for exponent = 0 to 15 do10        if value == candidate then return TRUE; end;11        candidate = candidate * 2;12    end;13    return FALSE;14end;15
16// TSize is a per-PE byte capacity. Physical rows are descriptor state derived17// exactly from that capacity, the physical column count, and the element type.18// Zero means that no legal 16-bit row count exists for the supplied shape.19pure func DerivedTileRows(capacity_bytes: integer {0..262144},20                          columns: integer {0..65535},21                          data_type: TileDataType) => integer {0..65535}22begin23    if capacity_bytes == 0 || !IsNonzeroPowerOfTwo(columns) then24        return 0;25    end;26    let capacity_bits: integer = capacity_bytes * 8;27    let row_bits: integer = columns * TileElementBits(data_type);28    if row_bits == 0 || capacity_bits MOD row_bits != 0 then return 0; end;29    let rows: integer = capacity_bits DIVRM row_bits;30    if rows == 0 || rows > 65535 then return 0; end;31    return rows as integer {0..65535};32end;33
34pure func TileShapeMatchesCapacity(capacity_bytes: integer {0..262144},35                                   rows: integer {0..65535},36                                   columns: integer {0..65535},37                                   data_type: TileDataType) => boolean38begin39    let derived_rows = DerivedTileRows(capacity_bytes, columns, data_type);40    return derived_rows != 0 && rows == derived_rows;41end;42