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157 lines
8.5 KiB
Systemverilog
157 lines
8.5 KiB
Systemverilog
///////////////////////////////////////////
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//
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// Written: me@KatherineParry.com
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// Modified: 7/5/2022
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//
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// Purpose: Fma shift calculation
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//
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// A component of the Wally configurable RISC-V project.
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//
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// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
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//
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// MIT LICENSE
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
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// to whom the Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or
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// substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
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// OR OTHER DEALINGS IN THE SOFTWARE.
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////////////////////////////////////////////////////////////////////////////////////////////////
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`include "wally-config.vh"
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module fmashiftcalc(
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input logic [3*`NF+5:0] FmaSm, // the positive sum
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input logic [`NE-1:0] Ze, // exponent of Z
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input logic [`NE+1:0] FmaPe, // X exponent + Y exponent - bias
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input logic [$clog2(3*`NF+7)-1:0] FmaNCnt, // normalization shift count
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input logic [`FMTBITS-1:0] Fmt, // precision 1 = double 0 = single
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input logic FmaKillProd, // is the product set to zero
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output logic [`NE+1:0] FmaNe, // exponent of the normalized sum not taking into account denormal or zero results
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output logic FmaSZero, // is the result denormalized - calculated before LZA corection
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output logic FmaPreResultDenorm, // is the result denormalized - calculated before LZA corection
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output logic [$clog2(3*`NF+7)-1:0] FmaShiftAmt, // normalization shift count
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output logic [3*`NF+8:0] FmaShiftIn // is the sum zero
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);
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logic [$clog2(3*`NF+7)-1:0] DenormShift; // right shift if the result is denormalized //***change this later
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logic [`NE+1:0] NormSumExp; // the exponent of the normalized sum with the `FLEN bias
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///////////////////////////////////////////////////////////////////////////////
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// Normalization
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///////////////////////////////////////////////////////////////////////////////
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//*** insert bias-bias simplification in fcvt.sv/phone pictures
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// Determine if the sum is zero
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assign FmaSZero = ~(|FmaSm);
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// calculate the sum's exponent
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// ProdExp - NormCnt - 1 + NF+4 = ProdExp + ~NormCnt + 1 - 1 + NF+4 = ProdExp + ~NormCnt + NF+4
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assign NormSumExp = (FmaKillProd ? {2'b0, Ze} : FmaPe) + {{`NE+2-$unsigned($clog2(3*`NF+7)){1'b1}}, ~FmaNCnt} + (`NE+2)'(`NF+4);
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//convert the sum's exponent into the proper percision
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if (`FPSIZES == 1) begin
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assign FmaNe = NormSumExp;
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end else if (`FPSIZES == 2) begin
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assign FmaNe = Fmt ? NormSumExp : (NormSumExp-(`NE+2)'(`BIAS)+(`NE+2)'(`BIAS1))&{`NE+2{|NormSumExp}};
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end else if (`FPSIZES == 3) begin
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always_comb begin
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case (Fmt)
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`FMT: FmaNe = NormSumExp;
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`FMT1: FmaNe = (NormSumExp-(`NE+2)'(`BIAS)+(`NE+2)'(`BIAS1))&{`NE+2{|NormSumExp}};
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`FMT2: FmaNe = (NormSumExp-(`NE+2)'(`BIAS)+(`NE+2)'(`BIAS2))&{`NE+2{|NormSumExp}};
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default: FmaNe = {`NE+2{1'bx}};
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endcase
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end
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end else if (`FPSIZES == 4) begin
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always_comb begin
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case (Fmt)
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2'h3: FmaNe = NormSumExp;
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2'h1: FmaNe = (NormSumExp-(`NE+2)'(`BIAS)+(`NE+2)'(`D_BIAS))&{`NE+2{|NormSumExp}};
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2'h0: FmaNe = (NormSumExp-(`NE+2)'(`BIAS)+(`NE+2)'(`S_BIAS))&{`NE+2{|NormSumExp}};
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2'h2: FmaNe = (NormSumExp-(`NE+2)'(`BIAS)+(`NE+2)'(`H_BIAS))&{`NE+2{|NormSumExp}};
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endcase
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end
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end
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// determine if the result is denormalized
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if (`FPSIZES == 1) begin
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logic Sum0LEZ, Sum0GEFL;
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assign Sum0LEZ = NormSumExp[`NE+1] | ~|NormSumExp;
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assign Sum0GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF)-(`NE+2)'(2));
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assign FmaPreResultDenorm = Sum0LEZ & Sum0GEFL & ~FmaSZero;
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end else if (`FPSIZES == 2) begin
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logic Sum0LEZ, Sum0GEFL, Sum1LEZ, Sum1GEFL;
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assign Sum0LEZ = NormSumExp[`NE+1] | ~|NormSumExp;
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assign Sum0GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF)-(`NE+2)'(2));
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assign Sum1LEZ = $signed(NormSumExp) <= $signed( (`NE+2)'(`BIAS)-(`NE+2)'(`BIAS1));
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assign Sum1GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF1+2)+(`NE+2)'(`BIAS)-(`NE+2)'(`BIAS1)) | ~|NormSumExp;
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assign FmaPreResultDenorm = (Fmt ? Sum0LEZ : Sum1LEZ) & (Fmt ? Sum0GEFL : Sum1GEFL) & ~FmaSZero;
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end else if (`FPSIZES == 3) begin
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logic Sum0LEZ, Sum0GEFL, Sum1LEZ, Sum1GEFL, Sum2LEZ, Sum2GEFL;
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assign Sum0LEZ = NormSumExp[`NE+1] | ~|NormSumExp;
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assign Sum0GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF)-(`NE+2)'(2));
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assign Sum1LEZ = $signed(NormSumExp) <= $signed( (`NE+2)'(`BIAS)-(`NE+2)'(`BIAS1));
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assign Sum1GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF1+2)+(`NE+2)'(`BIAS)-(`NE+2)'(`BIAS1)) | ~|NormSumExp;
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assign Sum2LEZ = $signed(NormSumExp) <= $signed( (`NE+2)'(`BIAS)-(`NE+2)'(`BIAS2));
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assign Sum2GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF2+2)+(`NE+2)'(`BIAS)-(`NE+2)'(`BIAS2)) | ~|NormSumExp;
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always_comb begin
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case (Fmt)
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`FMT: FmaPreResultDenorm = Sum0LEZ & Sum0GEFL & ~FmaSZero;
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`FMT1: FmaPreResultDenorm = Sum1LEZ & Sum1GEFL & ~FmaSZero;
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`FMT2: FmaPreResultDenorm = Sum2LEZ & Sum2GEFL & ~FmaSZero;
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default: FmaPreResultDenorm = 1'bx;
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endcase
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end
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end else if (`FPSIZES == 4) begin
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logic Sum0LEZ, Sum0GEFL, Sum1LEZ, Sum1GEFL, Sum2LEZ, Sum2GEFL, Sum3LEZ, Sum3GEFL;
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assign Sum0LEZ = NormSumExp[`NE+1] | ~|NormSumExp;
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assign Sum0GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`NF )-(`NE+2)'(2));
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assign Sum1LEZ = $signed(NormSumExp) <= $signed( (`NE+2)'(`BIAS)-(`NE+2)'(`D_BIAS));
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assign Sum1GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`D_NF+2)+(`NE+2)'(`BIAS)-(`NE+2)'(`D_BIAS)) | ~|NormSumExp;
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assign Sum2LEZ = $signed(NormSumExp) <= $signed( (`NE+2)'(`BIAS)-(`NE+2)'(`S_BIAS));
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assign Sum2GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`S_NF+2)+(`NE+2)'(`BIAS)-(`NE+2)'(`S_BIAS)) | ~|NormSumExp;
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assign Sum3LEZ = $signed(NormSumExp) <= $signed( (`NE+2)'(`BIAS)-(`NE+2)'(`H_BIAS));
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assign Sum3GEFL = $signed(NormSumExp) >= $signed(-(`NE+2)'(`H_NF+2)+(`NE+2)'(`BIAS)-(`NE+2)'(`H_BIAS)) | ~|NormSumExp;
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always_comb begin
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case (Fmt)
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2'h3: FmaPreResultDenorm = Sum0LEZ & Sum0GEFL & ~FmaSZero;
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2'h1: FmaPreResultDenorm = Sum1LEZ & Sum1GEFL & ~FmaSZero;
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2'h0: FmaPreResultDenorm = Sum2LEZ & Sum2GEFL & ~FmaSZero;
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2'h2: FmaPreResultDenorm = Sum3LEZ & Sum3GEFL & ~FmaSZero;
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endcase // *** remove checking to see if it's underflowed and only check for less than zero for denorm checking
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end
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end
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// 010. when should be 001.
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// - shift left one
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// - add one from exp
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// - if kill prod dont add to exp
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// Determine if the result is denormal
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// assign FmaPreResultDenorm = $signed(FmaNe)<=0 & ($signed(FmaNe)>=$signed(-FracLen)) & ~FmaSZero;
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// Determine the shift needed for denormal results
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// - if not denorm add 1 to shift out the leading 1
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assign DenormShift = FmaPreResultDenorm ? FmaNe[$clog2(3*`NF+7)-1:0] : 1;
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// set and calculate the shift input and amount
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// - shift once if killing a product and the result is denormalized
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assign FmaShiftIn = {3'b0, FmaSm};
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assign FmaShiftAmt = FmaNCnt+DenormShift;
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endmodule
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