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postprocessor shift amount simplification

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David Harris 2024-06-10 07:55:35 -07:00
parent 3284dd2112
commit e02c1008bc
3 changed files with 4 additions and 9 deletions
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4
src/fpu/postproc/divshiftcalc.sv
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@ -28,10 +28,8 @@
////////////////////////////////////////////////////////////////////////////////////////////////
module divshiftcalc import cvw::*; #(parameter cvw_t P) (
input logic [P.DIVb:0] DivUm, // divsqrt significand
input logic [P.NE+1:0] DivUe, // divsqrt exponent
output logic [P.LOGNORMSHIFTSZ-1:0] DivShiftAmt, // divsqrt shift amount
output logic [P.NORMSHIFTSZ-1:0] DivShiftIn, // divsqrt shift input
output logic DivResSubnorm, // is the divsqrt result subnormal
output logic DivSubnormShiftPos // is the subnormal shift amount positive
);
@ -68,6 +66,4 @@ module divshiftcalc import cvw::*; #(parameter cvw_t P) (
assign DivSubnormShiftAmt = DivSubnormShiftPos ? DivSubnormShift[P.LOGNORMSHIFTSZ-1:0] : '0;
assign DivShiftAmt = DivResSubnorm ? DivSubnormShiftAmt : NormShift;
// pre-shift the divider result for normalization
assign DivShiftIn = {{P.NF{1'b0}}, DivUm, {P.NORMSHIFTSZ-P.DIVb-1-P.NF{1'b0}}};
endmodule

4
src/fpu/postproc/fmashiftcalc.sv
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@ -53,6 +53,7 @@ module fmashiftcalc import cvw::*; #(parameter cvw_t P) (
//convert the sum's exponent into the proper precision
if (P.FPSIZES == 1) begin
assign NormSumExp = PreNormSumExp;
assign BiasCorr = '0;
end else if (P.FPSIZES == 2) begin
assign BiasCorr = Fmt ? (P.NE+2)'(0) : (P.NE+2)'(P.BIAS1-P.BIAS);
assign NormSumExp = PreNormSumExp+BiasCorr;
@ -129,6 +130,5 @@ module fmashiftcalc import cvw::*; #(parameter cvw_t P) (
// set and calculate the shift input and amount
// - shift once if killing a product and the result is subnormal
if (P.FPSIZES == 1) assign FmaShiftAmt = FmaPreResultSubnorm ? FmaSe[$clog2(P.FMALEN-1)-1:0]+($clog2(P.FMALEN-1))'(P.NF+3): FmaSCnt+1;
else assign FmaShiftAmt = FmaPreResultSubnorm ? FmaSe[$clog2(P.FMALEN-1)-1:0]+($clog2(P.FMALEN-1))'(P.NF+3)+BiasCorr[$clog2(P.FMALEN-1)-1:0]: FmaSCnt+1;
assign FmaShiftAmt = FmaPreResultSubnorm ? FmaSe[$clog2(P.FMALEN-1)-1:0]+($clog2(P.FMALEN-1))'(P.NF+3)+BiasCorr[$clog2(P.FMALEN-1)-1:0]: FmaSCnt+1;
endmodule

5
src/fpu/postproc/postprocess.sv
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@ -91,7 +91,6 @@ module postprocess import cvw::*; #(parameter cvw_t P) (
logic [$clog2(P.FMALEN+1)-1:0] FmaShiftAmt; // normalization shift amount for fma
// division signals
logic [P.LOGNORMSHIFTSZ-1:0] DivShiftAmt; // divsqrt shif amount
logic [P.NORMSHIFTSZ-1:0] DivShiftIn; // divsqrt shift input
logic [P.NE+1:0] Ue; // divsqrt corrected exponent after corretion shift
logic DivByZero; // divide by zero flag
logic DivResSubnorm; // is the divsqrt result subnormal
@ -147,7 +146,7 @@ module postprocess import cvw::*; #(parameter cvw_t P) (
fmashiftcalc #(P) fmashiftcalc(.FmaSCnt, .Fmt, .NormSumExp, .FmaSe, .FmaSm,
.FmaSZero, .FmaPreResultSubnorm, .FmaShiftAmt);
divshiftcalc #(P) divshiftcalc(.DivUe, .DivUm, .DivResSubnorm, .DivSubnormShiftPos, .DivShiftAmt, .DivShiftIn);
divshiftcalc #(P) divshiftcalc(.DivUe, .DivResSubnorm, .DivSubnormShiftPos, .DivShiftAmt);
// select which unit's output to shift
always_comb
@ -162,7 +161,7 @@ module postprocess import cvw::*; #(parameter cvw_t P) (
end
2'b01: begin //divsqrt
ShiftAmt = DivShiftAmt;
ShiftIn = DivShiftIn;
ShiftIn = {{P.NF{1'b0}}, DivUm, {P.NORMSHIFTSZ-P.DIVb-1-P.NF{1'b0}}};
end
default: begin
ShiftAmt = {P.LOGNORMSHIFTSZ{1'bx}};