Data Structure Registers¶

Data Structure Registers (DSRs) are physical registers that are used to store DSD values. Each DSR belongs to one of three DSR files, namely the dest, src0 and src1 DSR files. All DSD operations will actually operate on DSRs behind the scenes and therefore, all DSD operands to DSD operations must be loaded to DSRs before executing the respective DSD operation.

Certain operations on DSRs require Extended DSRs (XDSRs). In this case, the DSRs are augmented by the use of an XDSR, a physical register belonging to a separate file.

The allocation of DSRs and XDSRs, and the loading of DSDs to DSRs, is typically done automatically by the compiler.

However, it is also possible to create and use DSRs and XDSRs directly. This chapter describes how users can allocate DSRs and XDSRs and then load DSDs to DSRs explicitly without the compiler’s assistance.

DSR Types¶

There are 5 types of DSRs supported in CSL, each corresponding to one of the three DSR files. These are the following:

dsr_dest represents a DSR value that can only be used to store a destination operand to a DSD operation.
dsr_src0 represents a DSR value that can be used to store a source as well as a destination operand to a DSD operation.
dsr_src1 represents a DSR value that can be only be used to store a source operand to a DSD operation.
dsr_fifo_dest represents a dsr_dest DSR that is expected to store a FIFO (See FIFO DSR types).
dsr_fifo_src1 represents a dsr_src1 DSR that is expected to store a FIFO.

XDSR values are represented by the xdsr type.

FIFO DSR types¶

The dsr_fifo_dest and dsr_fifo_src1 types can be used instead of dsr_dest and dsr_src1, respectively, to represent DSRs that are known to store a FIFO if one does not have access to a FIFO object. Like FIFO objects, non-asynchronous DSD operations on FIFO DSRs will terminate and return false when reading from an empty FIFO or writing to a full FIFO. Otherwise, FIFO DSR-typed values have the same semantics as the corresponding non-FIFO DSR types.

Behavior is undefined if a FIFO DSR-typed value is not initialized as part of a FIFO when it is used in a DSD operation.

If a non-asynchronous DSD operation has a DSR operand that does not have FIFO DSR type, but that DSR holds a FIFO, behavior is undefined if that FIFO experiences a FIFO full or FIFO empty event. It is the programmer’s responsibility to avoid such FIFO full or FIFO empty events.

DSR Builtins¶

@get_dsr¶

Create a unique DSR identifier value. This value will uniquely identify a physical DSR along with its DSR file.

Syntax¶

@get_dsr(dsr_type, dsr_id);
@get_dsr(fifo_dsr_type, non_fifo_dsr);

Where:

dsr_type is an expression of type type and whose value must be one of the DSR types.
dsr_id is a comptime-known expression of integer type.
fifo_dsr_type is an expression of type type whose value is one of the FIFO DSR types (dsr_fifo_dest or dsr_fifo_src1).
non_fifo_dsr is a comptime-known expression of a non-FIFO DSR type.
Returns a value of dsr_type.

Example¶

const dsr1 = @get_dsr(dsr_dest, 0);
const dsr2 = @get_dsr(dsr_src0, 1);
const dsr3 = @get_dsr(dsr_src1, 6);
const dsr4 = @get_dsr(dsr_fifo_dest, 4);
const dsr5 = @get_dsr(dsr_fifo_src1, dsr3);

Semantics¶

Creates a unique DSR identifier value of dsr_type type using the specified integer identifier. This builtin must be evaluated at comptime. If the provided integer identifier has already been used for the given DSR type or it is outside the valid range of values for the given target architecture, then an error will be emitted.

The type of non_fifo_dsr must correspond to fifo_dsr_type. If fifo_dsr_type is dsr_fifo_dest, then non_fifo_dsr must have type dsr_dest, and if fifo_dsr_type is dsr_fifo_src1, then non_fifo_dsr must have type dsr_src1.

@get_xdsr¶

Create a unique XDSR identifier value. This value will uniquely identify a physical XDSR.

Syntax¶

@get_xdsr(xdsr_id);

Where:

xdsr_id is a comptime-known expression of integer type.
Returns a value of type xdsr.

Example¶

const my_xdsr = @get_xdsr(4);

Semantics¶

Creates a unique XDSR identifier value using the specified integer identifier. This builtin must be evaluated at comptime. If the provided integer identifier has already been used or it exceeds the valid range of values for the given target architecture, then an error will be emitted.

@load_to_dsr¶

Load a DSD value into a DSR.

Syntax¶

@load_to_dsr(dsr_value, dsd_value);
@load_to_dsr(dsr_value, dsd_value, config_struct);

Where:

dsr_value a comptime-known expression of a DSR type.
dsd_value an expression of DSD type.
config_struct optional anonymous struct consisting of either of the following:
- Asynchronous configuration setting fields as explained in Asynchronous DSD Operations. These are allowed only for fabric DSDs. The supported settings are:
  - async
  - activate
  - unblock
  - on_control
- The save_address setting field. This is allowed only for mem1d and mem4d DSDs. See save_address for more details.

Example¶

const dsr1 = @get_dsr(dsr_dest, 0);
const dsr2 = @get_dsr(dsr_src0, 1);

fn foo(mem_dsd: mem1d_dsd, fab_dsd: fabin_dsd) void {
  // Loads a memory DSD to a DSR.
  @load_to_dsr(dsr1, mem_dsd);

  // Loads a fabric DSD to a DSR while specifying that the
  // input DSD is asynchronous with activation and on_control settings.
  @load_to_dsr(dsr2, fab_dsd, .{.async = true,
                                .activate = callback,
                                .on_control = .{.terminate = true}});
}

const A = @zeros([10]f16);
const mem_dsd = @get_dsd(mem1d_dsd, .{.tensor_access = |i|{10} -> A[i]});
const fab_dsd = @get_dsd(fabin_dsd, .{.extent = 10,
                                      .fabric_color = @get_color(0),
                                      .input_queue = @get_input_queue(0)});

comptime {
  // The DSD will be loaded to the DSR at comptime, i.e., before the
  // program begins its execution.
  @load_to_dsr(dsr1, mem_dsd);

  // A fabric DSD with asynchronous properties will be loaded at comptime.
  @load_to_dsr(dsr2, fab_dsd, .{.async = true,
                                .activate = callback,
                                .on_control = .{.terminate = true}});
}

Semantics¶

The @load_to_dsr builtin can be called at comptime or runtime.

If it is called at runtime it will load the input DSD to the specified DSR at runtime.

If it is called at comptime, the specified DSD will be loaded to the DSR before the program begins executing.

A DSD of type fabin_dsd cannot be loaded to a dsr_dest DSR.

A DSD of type fabout_dsd cannot be loaded to a dsr_src0 or dsr_src1 DSRs.

FIFO DSRs are not permitted in @load_to_dsr.

save_address¶

The save_address option may be supplied to @load_to_dsr if the DSD is of the type mem1d_dsd or mem4d_dsd. This causes subsequent DSD operations on the DSR to update the DSR’s base address for the outermost (slowest-varying) dimension after termination to point one position past the end of the range covered by the DSD operation. The next operation on the DSR will effectively pick up where the previous one ended.

Example¶

const CHUNK_LENGTH = 4;
const N_CHUNKS = 3;

var chunks_in =
  [CHUNK_LENGTH * N_CHUNKS]i16 {
    0, 1, 2, 3,
    4, 5, 6, 7,
    8, 9, 10, 11
  };

var chunks_out = @zeros(
  [CHUNK_LENGTH * N_CHUNKS]i16
);

const chunks_in_dsd = @get_dsd(
  mem1d_dsd,
  .{ .tensor_access = |i|{CHUNK_LENGTH} -> chunks_in[i] }
);

const chunks_out_dsd = @get_dsd(
  mem1d_dsd,
  .{ .tensor_access = |i|{CHUNK_LENGTH} -> chunks_out[i] }
);

comptime {
  @load_to_dsr(chunks_out_dsr, chunks_out_dsd, .{ .save_address = true });
  @load_to_dsr(chunks_in_dsr, chunks_in_dsd, .{ .save_address = true });
}

task main() void {
  //
  // Each call to @mov16 will copy a chunk of size CHUNK_LENGTH, as
  // specified in the .tensor_access expression. The base address for both
  // the source and target operations will be incremented by CHUNK_LENGTH
  // each time.
  //
  // Thus the following loop is semantically equivalent to:
  //
  //     for (@range(i16, N_CHUNKS)) |i| {
  //       @mov16(chunks_out_dsr, chunks_in_dsr);
  //       @set_dsr_base_addr(chunks_out_dsr,
  //                          &chunks_out[CHUNK_LENGTH * (i+1)]);
  //       @set_dsr_base_addr(chunks_in_dsr,
  //                        &chunks_in[CHUNK_LENGTH * (i+1)]);
  //     }
  //
  for (@range(i16, N_CHUNKS)) |i| {
    @mov16(chunks_out_dsr, chunks_in_dsr);
  }
}

@allocate_fifo with DSRs¶

By default, the DSRs and XDSR used by @allocate_fifo (see FIFOs) are allocated by the compiler. However, it supports the use of user-specified DSRs and XDSR as well, using the following syntax:

@allocate_fifo(fifo_buffer, config_struct);

Where, in order to allocate a FIFO with user-specified DSRs and XDSR, config_struct must contain the fields:

dest: a comptime-known expression of dsr_dest type.
src: a comptime-known expression of dsr_src1 type.
xdsr: a comptime-known expression of xdsr type.

The fields dest, src, and xdsr must all be specified together, or all absent, otherwise an error will be emitted. The integer identifiers of dest and src must match. If the provided DSR and XDSR identifiers have already been used for their respective types or exceed the valid range of values for the given target architecture, then an error will be emitted.

Other fields of config_struct described in Task Activation on Pop and Push retain their same semantics when the DSRs and XDSR are specified.

Example¶

var buf = @zeros([240]u16);
const my_fifo = @allocate_fifo(buf, .{
   .dest = @get_dsr(dsr_dest, 4),
   .src = @get_dsr(dsr_src1, 4),
   .xdsr = @get_xdsr(1)});

SDK Documentation (1.3.0)

Data Structure Registers

Contents

Data Structure Registers¶

DSR Types¶

FIFO DSR types¶

DSR Builtins¶

@get_dsr¶

Syntax¶

Example¶

Semantics¶

@get_xdsr¶

Syntax¶

Example¶

Semantics¶

@load_to_dsr¶

Syntax¶

Example¶

Semantics¶

save_address¶

Example¶

@allocate_fifo with DSRs¶

Example¶