verilog/rtl/fpnew_pkg.sv

// Copyright 2019 ETH Zurich and University of Bologna.
//
// Copyright and related rights are licensed under the Solderpad Hardware
// License, Version 0.51 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://solderpad.org/licenses/SHL-0.51. Unless required by applicable law
// or agreed to in writing, software, hardware and materials distributed under
// this License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.

// Author: Stefan Mach <smach@iis.ee.ethz.ch>

package fpnew_pkg;

  // ---------
  // FP TYPES
  // ---------
  // | Enumerator | Format           | Width  | EXP_BITS | MAN_BITS
  // |:----------:|------------------|-------:|:--------:|:--------:
  // | FP32       | IEEE binary32    | 32 bit | 8        | 23
  // | FP64       | IEEE binary64    | 64 bit | 11       | 52
  // | FP16       | IEEE binary16    | 16 bit | 5        | 10
  // | FP8        | binary8          |  8 bit | 5        | 2
  // | FP16ALT    | binary16alt      | 16 bit | 8        | 7
  // *NOTE:* Add new formats only at the end of the enumeration for backwards compatibilty!

  // Encoding for a format
  typedef struct packed {
    int unsigned exp_bits;
    int unsigned man_bits;
  } fp_encoding_t;

  localparam int unsigned NUM_FP_FORMATS = 5; // change me to add formats
  localparam int unsigned FP_FORMAT_BITS = $clog2(NUM_FP_FORMATS);

  // FP formats
  typedef enum logic [FP_FORMAT_BITS-1:0] {
    FP32    = 'd0,
    FP64    = 'd1,
    FP16    = 'd2,
    FP8     = 'd3,
    FP16ALT = 'd4
    // add new formats here
  } fp_format_e;

  // Encodings for supported FP formats
  localparam fp_encoding_t [0:NUM_FP_FORMATS-1] FP_ENCODINGS  = '{
    '{8,  23}, // IEEE binary32 (single)
    '{11, 52}, // IEEE binary64 (double)
    '{5,  10}, // IEEE binary16 (half)
    '{5,  2},  // custom binary8
    '{8,  7}   // custom binary16alt
    // add new formats here
  };

  typedef logic [0:NUM_FP_FORMATS-1]       fmt_logic_t;    // Logic indexed by FP format (for masks)
  typedef logic [0:NUM_FP_FORMATS-1][31:0] fmt_unsigned_t; // Unsigned indexed by FP format

  localparam fmt_logic_t CPK_FORMATS = 5'b11000; // FP32 and FP64 can provide CPK only

  // ---------
  // INT TYPES
  // ---------
  // | Enumerator | Width  |
  // |:----------:|-------:|
  // | INT8       |  8 bit |
  // | INT16      | 16 bit |
  // | INT32      | 32 bit |
  // | INT64      | 64 bit |
  // *NOTE:* Add new formats only at the end of the enumeration for backwards compatibilty!

  localparam int unsigned NUM_INT_FORMATS = 4; // change me to add formats
  localparam int unsigned INT_FORMAT_BITS = $clog2(NUM_INT_FORMATS);

  // Int formats
  typedef enum logic [INT_FORMAT_BITS-1:0] {
    INT8,
    INT16,
    INT32,
    INT64
    // add new formats here
  } int_format_e;

  // Returns the width of an INT format by index
  function automatic int unsigned int_width(int_format_e ifmt);
    unique case (ifmt)
      INT8:  return 8;
      INT16: return 16;
      INT32: return 32;
      INT64: return 64;
     // default: begin
        // pragma translate_off
       // $fatal(1, "Invalid INT format supplied");
        // pragma translate_on
        // just return any integer to avoid any latches
        // hopefully this error is caught by simulation
        //return INT8;
      //end
    endcase
  endfunction

  typedef logic [0:NUM_INT_FORMATS-1] ifmt_logic_t; // Logic indexed by INT format (for masks)

  // --------------
  // FP OPERATIONS
  // --------------
  localparam int unsigned NUM_OPGROUPS = 4;

  // Each FP operation belongs to an operation group
  typedef enum logic [1:0] {
    ADDMUL, DIVSQRT, NONCOMP, CONV
  } opgroup_e;

  localparam int unsigned OP_BITS = 4;

  typedef enum logic [OP_BITS-1:0] {
    FMADD, FNMSUB, ADD, MUL,     // ADDMUL operation group
    DIV, SQRT,                   // DIVSQRT operation group
    SGNJ, MINMAX, CMP, CLASSIFY, // NONCOMP operation group
    F2F, F2I, I2F, CPKAB, CPKCD  // CONV operation group
  } operation_e;

  // -------------------
  // RISC-V FP-SPECIFIC
  // -------------------
  // Rounding modes
  typedef enum logic [2:0] {
    RNE = 3'b000,
    RTZ = 3'b001,
    RDN = 3'b010,
    RUP = 3'b011,
    RMM = 3'b100,
    DYN = 3'b111
  } roundmode_e;

  // Status flags
  typedef struct packed {
    logic NV; // Invalid
    logic DZ; // Divide by zero
    logic OF; // Overflow
    logic UF; // Underflow
    logic NX; // Inexact
  } status_t;

  // Information about a floating point value
  typedef struct packed {
    logic is_normal;     // is the value normal
    logic is_subnormal;  // is the value subnormal
    logic is_zero;       // is the value zero
    logic is_inf;        // is the value infinity
    logic is_nan;        // is the value NaN
    logic is_signalling; // is the value a signalling NaN
    logic is_quiet;      // is the value a quiet NaN
    logic is_boxed;      // is the value properly NaN-boxed (RISC-V specific)
  } fp_info_t;

  // Classification mask
  typedef enum logic [9:0] {
    NEGINF     = 10'b00_0000_0001,
    NEGNORM    = 10'b00_0000_0010,
    NEGSUBNORM = 10'b00_0000_0100,
    NEGZERO    = 10'b00_0000_1000,
    POSZERO    = 10'b00_0001_0000,
    POSSUBNORM = 10'b00_0010_0000,
    POSNORM    = 10'b00_0100_0000,
    POSINF     = 10'b00_1000_0000,
    SNAN       = 10'b01_0000_0000,
    QNAN       = 10'b10_0000_0000
  } classmask_e;

  // ------------------
  // FPU configuration
  // ------------------
  // Pipelining registers can be inserted (at elaboration time) into operational units
  typedef enum logic [1:0] {
    BEFORE,     // registers are inserted at the inputs of the unit
    AFTER,      // registers are inserted at the outputs of the unit
    INSIDE,     // registers are inserted at predetermined (suboptimal) locations in the unit
    DISTRIBUTED // registers are evenly distributed, INSIDE >= AFTER >= BEFORE
  } pipe_config_t;

  // Arithmetic units can be arranged in parallel (per format), merged (multi-format) or not at all.
  typedef enum logic [1:0] {
    DISABLED, // arithmetic units are not generated
    PARALLEL, // arithmetic units are generated in prallel slices, one for each format
    MERGED    // arithmetic units are contained within a merged unit holding multiple formats
  } unit_type_t;

  // Array of unit types indexed by format
  typedef unit_type_t [0:NUM_FP_FORMATS-1] fmt_unit_types_t;

  // Array of format-specific unit types by opgroup
  typedef fmt_unit_types_t [0:NUM_OPGROUPS-1] opgrp_fmt_unit_types_t;
  // same with unsigned
  typedef fmt_unsigned_t [0:NUM_OPGROUPS-1] opgrp_fmt_unsigned_t;

  // FPU configuration: features
  typedef struct packed {
    int unsigned Width;
    logic        EnableVectors;
    logic        EnableNanBox;
    fmt_logic_t  FpFmtMask;
    ifmt_logic_t IntFmtMask;
  } fpu_features_t;

  localparam fpu_features_t RV64D = '{
    Width:         64,
    EnableVectors: 1'b0,
    EnableNanBox:  1'b1,
    FpFmtMask:     5'b11000,
    IntFmtMask:    4'b0011
  };

  localparam fpu_features_t RV32D = '{
    Width:         64,
    EnableVectors: 1'b1,
    EnableNanBox:  1'b1,
    FpFmtMask:     5'b11000,
    IntFmtMask:    4'b0010
  };

  localparam fpu_features_t RV32F = '{
    Width:         32,
    EnableVectors: 1'b0,
    EnableNanBox:  1'b1,
    FpFmtMask:     5'b10000,
    IntFmtMask:    4'b0010
  };

  localparam fpu_features_t RV64D_Xsflt = '{
    Width:         64,
    EnableVectors: 1'b1,
    EnableNanBox:  1'b1,
    FpFmtMask:     5'b11111,
    IntFmtMask:    4'b1111
  };

  localparam fpu_features_t RV32F_Xsflt = '{
    Width:         32,
    EnableVectors: 1'b1,
    EnableNanBox:  1'b1,
    FpFmtMask:     5'b10111,
    IntFmtMask:    4'b1110
  };

  localparam fpu_features_t RV32F_Xf16alt_Xfvec = '{
    Width:         32,
    EnableVectors: 1'b1,
    EnableNanBox:  1'b1,
    FpFmtMask:     5'b10001,
    IntFmtMask:    4'b0110
  };

  // FPU configuraion: implementation
  typedef struct packed {
    opgrp_fmt_unsigned_t   PipeRegs;
    opgrp_fmt_unit_types_t UnitTypes;
    pipe_config_t          PipeConfig;
  } fpu_implementation_t;

  localparam fpu_implementation_t DEFAULT_NOREGS = '{
    PipeRegs:   '{default: 0},
    UnitTypes:  '{'{default: PARALLEL}, // ADDMUL
                  '{default: MERGED},   // DIVSQRT
                  '{default: PARALLEL}, // NONCOMP
                  '{default: MERGED}},  // CONV
    PipeConfig: BEFORE
  };

  localparam fpu_implementation_t DEFAULT_SNITCH = '{
    PipeRegs:   '{default: 1},
    UnitTypes:  '{'{default: PARALLEL}, // ADDMUL
                  '{default: DISABLED}, // DIVSQRT
                  '{default: PARALLEL}, // NONCOMP
                  '{default: MERGED}},  // CONV
    PipeConfig: BEFORE
  };

  // -----------------------
  // Synthesis optimization
  // -----------------------
  localparam logic DONT_CARE = 1'b1; // the value to assign as don't care

  // -------------------------
  // General helper functions
  // -------------------------
  function automatic int minimum(int a, int b);
    return (a < b) ? a : b;
  endfunction

  function automatic int maximum(int a, int b);
    return (a > b) ? a : b;
  endfunction

  // -------------------------------------------
  // Helper functions for FP formats and values
  // -------------------------------------------
  // Returns the width of a FP format
  function automatic int unsigned fp_width(fp_format_e fmt);
    return FP_ENCODINGS[fmt].exp_bits + FP_ENCODINGS[fmt].man_bits + 1;
  endfunction

  // Returns the widest FP format present
  function automatic int unsigned max_fp_width(fmt_logic_t cfg);
    automatic int unsigned res = 0;
    for (int unsigned i = 0; i < NUM_FP_FORMATS; i++)
      if (cfg[i])
        res = unsigned'(maximum(res, fp_width(fp_format_e'(i))));
    return res;
  endfunction

  // Returns the narrowest FP format present
  function automatic int unsigned min_fp_width(fmt_logic_t cfg);
    automatic int unsigned res = max_fp_width(cfg);
    for (int unsigned i = 0; i < NUM_FP_FORMATS; i++)
      if (cfg[i])
        res = unsigned'(minimum(res, fp_width(fp_format_e'(i))));
    return res;
  endfunction

  // Returns the number of expoent bits for a format
  function automatic int unsigned exp_bits(fp_format_e fmt);
    return FP_ENCODINGS[fmt].exp_bits;
  endfunction

  // Returns the number of mantissa bits for a format
  function automatic int unsigned man_bits(fp_format_e fmt);
    return FP_ENCODINGS[fmt].man_bits;
  endfunction

  // Returns the bias value for a given format (as per IEEE 754-2008)
  function automatic int unsigned bias(fp_format_e fmt);
    return unsigned'(2**(FP_ENCODINGS[fmt].exp_bits-1)-1); // symmetrical bias
  endfunction

  function automatic fp_encoding_t super_format(fmt_logic_t cfg);
    automatic fp_encoding_t res;
    res = '0;
    for (int unsigned fmt = 0; fmt < NUM_FP_FORMATS; fmt++)
      if (cfg[fmt]) begin // only active format
        res.exp_bits = unsigned'(maximum(res.exp_bits, exp_bits(fp_format_e'(fmt))));
        res.man_bits = unsigned'(maximum(res.man_bits, man_bits(fp_format_e'(fmt))));
      end
    return res;
  endfunction

  // -------------------------------------------
  // Helper functions for INT formats and values
  // -------------------------------------------
  // Returns the widest INT format present
  function automatic int unsigned max_int_width(ifmt_logic_t cfg);
    automatic int unsigned res = 0;
    for (int ifmt = 0; ifmt < NUM_INT_FORMATS; ifmt++) begin
      if (cfg[ifmt]) res = maximum(res, int_width(int_format_e'(ifmt)));
    end
    return res;
  endfunction

  // --------------------------------------------------
  // Helper functions for operations and FPU structure
  // --------------------------------------------------
  // Returns the operation group of the given operation
  function automatic opgroup_e get_opgroup(operation_e op);
    unique case (op)
      FMADD, FNMSUB, ADD, MUL:     return ADDMUL;
      DIV, SQRT:                   return DIVSQRT;
      SGNJ, MINMAX, CMP, CLASSIFY: return NONCOMP;
      F2F, F2I, I2F, CPKAB, CPKCD: return CONV;
      default:                     return NONCOMP;
    endcase
  endfunction

  // Returns the number of operands by operation group
  function automatic int unsigned num_operands(opgroup_e grp);
    unique case (grp)
      ADDMUL:  return 3;
      DIVSQRT: return 2;
      NONCOMP: return 2;
      CONV:    return 3; // vectorial casts use 3 operands
      default: return 0;
    endcase
  endfunction

  // Returns the number of lanes according to width, format and vectors
  function automatic int unsigned num_lanes(int unsigned width, fp_format_e fmt, logic vec);
    return vec ? width / fp_width(fmt) : 1; // if no vectors, only one lane
  endfunction

  // Returns the maximum number of lanes in the FPU according to width, format config and vectors
  function automatic int unsigned max_num_lanes(int unsigned width, fmt_logic_t cfg, logic vec);
    return vec ? width / min_fp_width(cfg) : 1; // if no vectors, only one lane
  endfunction

  // Returns a mask of active FP formats that are present in lane lane_no of a multiformat slice
  function automatic fmt_logic_t get_lane_formats(int unsigned width,
                                                  fmt_logic_t cfg,
                                                  int unsigned lane_no);
    automatic fmt_logic_t res;
    for (int unsigned fmt = 0; fmt < NUM_FP_FORMATS; fmt++)
      // Mask active formats with the number of lanes for that format
      res[fmt] = cfg[fmt] & (width / fp_width(fp_format_e'(fmt)) > lane_no);
    return res;
  endfunction

  // Returns a mask of active INT formats that are present in lane lane_no of a multiformat slice
  function automatic ifmt_logic_t get_lane_int_formats(int unsigned width,
                                                       fmt_logic_t cfg,
                                                       ifmt_logic_t icfg,
                                                       int unsigned lane_no);
    automatic ifmt_logic_t res;
    automatic fmt_logic_t lanefmts;
    res = '0;
    lanefmts = get_lane_formats(width, cfg, lane_no);

    for (int unsigned ifmt = 0; ifmt < NUM_INT_FORMATS; ifmt++)
      for (int unsigned fmt = 0; fmt < NUM_FP_FORMATS; fmt++)
        // Mask active int formats with the width of the float formats
        if ((fp_width(fp_format_e'(fmt)) == int_width(int_format_e'(ifmt))))
          res[ifmt] |= icfg[ifmt] && lanefmts[fmt];
    return res;
  endfunction

  // Returns a mask of active FP formats that are present in lane lane_no of a CONV slice
  function automatic fmt_logic_t get_conv_lane_formats(int unsigned width,
                                                       fmt_logic_t cfg,
                                                       int unsigned lane_no);
    automatic fmt_logic_t res;
    for (int unsigned fmt = 0; fmt < NUM_FP_FORMATS; fmt++)
      // Mask active formats with the number of lanes for that format, CPK at least twice
      res[fmt] = cfg[fmt] && ((width / fp_width(fp_format_e'(fmt)) > lane_no) ||
                             (CPK_FORMATS[fmt] && (lane_no < 2)));
    return res;
  endfunction

  // Returns a mask of active INT formats that are present in lane lane_no of a CONV slice
  function automatic ifmt_logic_t get_conv_lane_int_formats(int unsigned width,
                                                            fmt_logic_t cfg,
                                                            ifmt_logic_t icfg,
                                                            int unsigned lane_no);
    automatic ifmt_logic_t res;
    automatic fmt_logic_t lanefmts;
    res = '0;
    lanefmts = get_conv_lane_formats(width, cfg, lane_no);

    for (int unsigned ifmt = 0; ifmt < NUM_INT_FORMATS; ifmt++)
      for (int unsigned fmt = 0; fmt < NUM_FP_FORMATS; fmt++)
        // Mask active int formats with the width of the float formats
        res[ifmt] |= icfg[ifmt] && lanefmts[fmt] &&
                     (fp_width(fp_format_e'(fmt)) == int_width(int_format_e'(ifmt)));
    return res;
  endfunction

  // Return whether any active format is set as MERGED
  function automatic logic any_enabled_multi(fmt_unit_types_t types, fmt_logic_t cfg);
    for (int unsigned i = 0; i < NUM_FP_FORMATS; i++)
      if (cfg[i] && types[i] == MERGED)
        return 1'b1;
      return 1'b0;
  endfunction

  // Return whether the given format is the first active one set as MERGED
  function automatic logic is_first_enabled_multi(fp_format_e fmt,
                                                  fmt_unit_types_t types,
                                                  fmt_logic_t cfg);
    for (int unsigned i = 0; i < NUM_FP_FORMATS; i++) begin
      if (cfg[i] && types[i] == MERGED) return (fp_format_e'(i) == fmt);
    end
    return 1'b0;
  endfunction

  // Returns the first format that is active and is set as MERGED
  function automatic fp_format_e get_first_enabled_multi(fmt_unit_types_t types, fmt_logic_t cfg);
    for (int unsigned i = 0; i < NUM_FP_FORMATS; i++)
      if (cfg[i] && types[i] == MERGED)
        return fp_format_e'(i);
      return fp_format_e'(0);
  endfunction

  // Returns the largest number of regs that is active and is set as MERGED
  function automatic int unsigned get_num_regs_multi(fmt_unsigned_t regs,
                                                     fmt_unit_types_t types,
                                                     fmt_logic_t cfg);
    automatic int unsigned res = 0;
    for (int unsigned i = 0; i < NUM_FP_FORMATS; i++) begin
      if (cfg[i] && types[i] == MERGED) res = maximum(res, regs[i]);
    end
    return res;
  endfunction

endpackage