forked from Github_Repos/cvw
41 lines
3.2 KiB
Systemverilog
41 lines
3.2 KiB
Systemverilog
`include "wally-config.vh"
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module lzacorrection(
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input logic [`NORMSHIFTSZ-1:0] Shifted, // the shifted sum before LZA correction
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input logic FmaOp,
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input logic DivOp,
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input logic DivResDenorm,
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input logic [`NE+1:0] DivCalcExpM,
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input logic [`NE+1:0] DivDenormShift,
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input logic [`NE+1:0] ConvNormSumExp, // exponent of the normalized sum not taking into account denormal or zero results
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input logic PreResultDenorm, // is the result denormalized - calculated before LZA corection
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input logic KillProdM, // is the product set to zero
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input logic SumZero,
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output logic [`CORRSHIFTSZ-1:0] CorrShifted, // the shifted sum before LZA correction
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output logic [`NE+1:0] CorrDivExp,
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output logic [`NE+1:0] SumExp // exponent of the normalized sum
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);
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logic [3*`NF+5:0] CorrSumShifted; // the shifted sum after LZA correction
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logic [`CORRSHIFTSZ:0] CorrQuotShifted;
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logic ResDenorm; // is the result denormalized
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logic LZAPlus1, LZAPlus2; // add one or two to the sum's exponent due to LZA correction
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// LZA correction
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assign LZAPlus1 = Shifted[`NORMSHIFTSZ-2];
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assign LZAPlus2 = Shifted[`NORMSHIFTSZ-1];
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// the only possible mantissa for a plus two is all zeroes - a one has to propigate all the way through a sum. so we can leave the bottom statement alone
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assign CorrSumShifted = LZAPlus1 ? Shifted[`NORMSHIFTSZ-3:1] : Shifted[`NORMSHIFTSZ-4:0];
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// if the msb is 1 or the exponent was one, but the shifted quotent was < 1 (Denorm)
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assign CorrQuotShifted = {LZAPlus2|(DivCalcExpM==1&~LZAPlus2) ? Shifted[`NORMSHIFTSZ-1:`NORMSHIFTSZ-`CORRSHIFTSZ] : {Shifted[`NORMSHIFTSZ-2:`NORMSHIFTSZ-`CORRSHIFTSZ], 1'b0}, 1'b0};
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// if the result of the divider was calculated to be denormalized, then the result was correctly normalized, so select the top shifted bits
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assign CorrShifted = FmaOp ? {CorrSumShifted, {`CORRSHIFTSZ-(3*`NF+6){1'b0}}} : DivOp&~DivResDenorm ? CorrQuotShifted[`CORRSHIFTSZ-1:0] : Shifted[`NORMSHIFTSZ-1:`NORMSHIFTSZ-`CORRSHIFTSZ];
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// Determine sum's exponent
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// if plus1 If plus2 if said denorm but norm plus 1 if said denorm but norm plus 2
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assign SumExp = (ConvNormSumExp+{{`NE+1{1'b0}}, LZAPlus1&~KillProdM}+{{`NE{1'b0}}, LZAPlus2&~KillProdM, 1'b0}+{{`NE+1{1'b0}}, ~ResDenorm&PreResultDenorm&~KillProdM}+{{`NE+1{1'b0}}, &ConvNormSumExp&Shifted[3*`NF+6]&~KillProdM}) & {`NE+2{~(SumZero|ResDenorm)}};
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// recalculate if the result is denormalized
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assign ResDenorm = PreResultDenorm&~Shifted[`NORMSHIFTSZ-3]&~Shifted[`NORMSHIFTSZ-2];
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// the quotent is in the range [.5,2) if there is no early termination
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// if the quotent < 1 and not denormal then subtract 1 to account for the normalization shift
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assign CorrDivExp = ((DivResDenorm)&~DivDenormShift[`NE+1]) ? (`NE+2)'(0) : DivCalcExpM - {(`NE+1)'(0), ~LZAPlus2};
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endmodule |