/////////////////////////////////////////// // fcmp.sv // // Written: me@KatherineParry.com // Modified: 7/5/2022 // // Purpose: Floating-point comparison unit // // Documentation: RISC-V System on Chip Design Chapter 13 // // A component of the CORE-V-WALLY configurable RISC-V project. // // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University // // SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1 // // Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file // except in compliance with the License, or, at your option, the Apache License version 2.0. You // may obtain a copy of the License at // // https://solderpad.org/licenses/SHL-2.1/ // // Unless required by applicable law or agreed to in writing, any work distributed under the // 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. //////////////////////////////////////////////////////////////////////////////////////////////// `include "wally-config.vh" // OpCtrl values // 110 min // 101 max // 010 equal // 001 less than // 011 less than or equal module fcmp ( input logic [`FMTBITS-1:0] Fmt, // format of fp number input logic [2:0] OpCtrl, // see above table input logic Xs, Ys, // input signs input logic [`NE-1:0] Xe, Ye, // input exponents input logic [`NF:0] Xm, Ym, // input mantissa input logic XZero, YZero, // is zero input logic XNaN, YNaN, // is NaN input logic XSNaN, YSNaN, // is signaling NaN input logic [`FLEN-1:0] X, Y, // original inputs (before unpacker) output logic CmpNV, // invalid flag output logic [`FLEN-1:0] CmpFpRes, // compare floating-point result output logic [`XLEN-1:0] CmpIntRes // compare integer result ); logic LTabs, LT, EQ; // is X < or > or = Y logic [`FLEN-1:0] NaNRes; // NaN result logic BothZero; // are both inputs zero logic EitherNaN, EitherSNaN; // are either input a (signaling) NaN assign LTabs= {1'b0, Xe, Xm} < {1'b0, Ye, Ym}; // unsigned comparison, treating FP as integers assign LT = (Xs & ~Ys) | (Xs & Ys & ~LTabs & ~EQ) | (~Xs & ~Ys & LTabs); // signed comparison assign EQ = (X == Y); assign BothZero = XZero&YZero; assign EitherNaN = XNaN|YNaN; assign EitherSNaN = XSNaN|YSNaN; // flags // Min/Max - if an input is a signaling NaN set invalid flag // LT/LE - signaling - sets invalid if NaN input // EQ - quiet - sets invalid if signaling NaN input always_comb begin case (OpCtrl[2:0]) 3'b110: CmpNV = EitherSNaN;//min 3'b101: CmpNV = EitherSNaN;//max 3'b010: CmpNV = EitherSNaN;//equal 3'b001: CmpNV = EitherNaN;//less than 3'b011: CmpNV = EitherNaN;//less than or equal default: CmpNV = 1'bx; endcase end // fmin/fmax of two NaNs returns a quiet NaN of the appropriate size // for IEEE, return the payload of X // for RISC-V, return the canonical NaN // select the NaN result if (`FPSIZES == 1) if(`IEEE754) assign NaNRes = {Xs, {`NE{1'b1}}, 1'b1, Xm[`NF-2:0]}; else assign NaNRes = {1'b0, {`NE{1'b1}}, 1'b1, {`NF-1{1'b0}}}; else if (`FPSIZES == 2) if(`IEEE754) assign NaNRes = Fmt ? {Xs, {`NE{1'b1}}, 1'b1, Xm[`NF-2:0]} : {{`FLEN-`LEN1{1'b1}}, Xs, {`NE1{1'b1}}, 1'b1, Xm[`NF-2:`NF-`NF1]}; else assign NaNRes = Fmt ? {1'b0, {`NE{1'b1}}, 1'b1, {`NF-1{1'b0}}} : {{`FLEN-`LEN1{1'b1}}, 1'b0, {`NE1{1'b1}}, 1'b1, (`NF1-1)'(0)}; else if (`FPSIZES == 3) always_comb case (Fmt) `FMT: if(`IEEE754) NaNRes = {Xs, {`NE{1'b1}}, 1'b1, Xm[`NF-2:0]}; else NaNRes = {1'b0, {`NE{1'b1}}, 1'b1, {`NF-1{1'b0}}}; `FMT1: if(`IEEE754) NaNRes = {{`FLEN-`LEN1{1'b1}}, Xs, {`NE1{1'b1}}, 1'b1, Xm[`NF-2:`NF-`NF1]}; else NaNRes = {{`FLEN-`LEN1{1'b1}}, 1'b0, {`NE1{1'b1}}, 1'b1, (`NF1-1)'(0)}; `FMT2: if(`IEEE754) NaNRes = {{`FLEN-`LEN2{1'b1}}, Xs, {`NE2{1'b1}}, 1'b1, Xm[`NF-2:`NF-`NF2]}; else NaNRes = {{`FLEN-`LEN2{1'b1}}, 1'b0, {`NE2{1'b1}}, 1'b1, (`NF2-1)'(0)}; default: NaNRes = {`FLEN{1'bx}}; endcase else if (`FPSIZES == 4) always_comb case (Fmt) 2'h3: if(`IEEE754) NaNRes = {Xs, {`NE{1'b1}}, 1'b1, Xm[`NF-2:0]}; else NaNRes = {1'b0, {`NE{1'b1}}, 1'b1, {`NF-1{1'b0}}}; 2'h1: if(`IEEE754) NaNRes = {{`FLEN-`D_LEN{1'b1}}, Xs, {`D_NE{1'b1}}, 1'b1, Xm[`NF-2:`NF-`D_NF]}; else NaNRes = {{`FLEN-`D_LEN{1'b1}}, 1'b0, {`D_NE{1'b1}}, 1'b1, (`D_NF-1)'(0)}; 2'h0: if(`IEEE754) NaNRes = {{`FLEN-`S_LEN{1'b1}}, Xs, {`S_NE{1'b1}}, 1'b1, Xm[`NF-2:`NF-`S_NF]}; else NaNRes = {{`FLEN-`S_LEN{1'b1}}, 1'b0, {`S_NE{1'b1}}, 1'b1, (`S_NF-1)'(0)}; 2'h2: if(`IEEE754) NaNRes = {{`FLEN-`H_LEN{1'b1}}, Xs, {`H_NE{1'b1}}, 1'b1, Xm[`NF-2:`NF-`H_NF]}; else NaNRes = {{`FLEN-`H_LEN{1'b1}}, 1'b0, {`H_NE{1'b1}}, 1'b1, (`H_NF-1)'(0)}; endcase // Min/Max // - outputs the min/max of X and Y // - -0 < 0 // - if both are NaN return quiet X // - if one is a NaN output the non-NaN always_comb if(OpCtrl[0]) // MAX if(XNaN) if(YNaN) CmpFpRes = NaNRes; // X = NaN Y = NaN else CmpFpRes = Y; // X = NaN Y != NaN else if(YNaN) CmpFpRes = X; // X != NaN Y = NaN else // X,Y != NaN if(LT) CmpFpRes = Y; // X < Y else CmpFpRes = X; // X > Y else // MIN if(XNaN) if(YNaN) CmpFpRes = NaNRes; // X = NaN Y = NaN else CmpFpRes = Y; // X = NaN Y != NaN else if(YNaN) CmpFpRes = X; // X != NaN Y = NaN else // X,Y != NaN if(LT) CmpFpRes = X; // X < Y else CmpFpRes = Y; // X > Y // LT/LE/EQ // - -0 = 0 // - inf = inf and -inf = -inf // - return 0 if comparison with NaN (unordered) assign CmpIntRes = {(`XLEN-1)'(0), (((EQ|BothZero)&OpCtrl[1])|(LT&OpCtrl[0]&~BothZero))&~EitherNaN}; endmodule