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Checking in radix 4 square root with qsel, fgen, softc, but not working

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This commit is contained in:
David Harris 2022-08-31 10:54:50 -07:00
parent 48a1abf06f
commit 09456db445
4 changed files with 82 additions and 12 deletions
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2
pipelined/config/shared/wally-shared.vh
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@ -102,7 +102,7 @@
// division constants
`define RADIX 32'h4
`define DIVCOPIES 32'h2
`define DIVCOPIES 32'h1
`define DIVLEN ((`NF < `XLEN) ? (`XLEN) : (`NF + 3))
// `define DIVN (`NF < `XLEN ? `XLEN : `NF+1) // length of input
`define DIVN (`NF < `XLEN ? `XLEN : `NF+3) // length of input

11
pipelined/src/fpu/fdivsqrtfsm.sv
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@ -90,20 +90,20 @@ module fdivsqrtfsm(
end
if (`RADIX == 2) begin
logic [`DIVb+3:0] FZero, FSticky;
logic [`DIVb+3:0] FZeroD, FSticky;
logic [`DIVb+2:0] LastK, FirstK;
assign LastK = ({3'b111, LastC} & ~({3'b111, LastC} << 1));
assign FirstK = ({3'b111, FirstC<<1} & ~({3'b111, FirstC<<1} << 1));
assign FZero = SqrtM ? {LastSM[`DIVb], LastSM, 2'b0} | {LastK,1'b0} : {3'b1,D,{`DIVb-`DIVN+2{1'b0}}};
assign FZeroD = SqrtM ? {FirstSM[`DIVb], FirstSM, 2'b0} | {FirstK,1'b0} : {3'b1,D,{`DIVb-`DIVN+2{1'b0}}};
assign FSticky = SqrtM ? {FirstSM[`DIVb], FirstSM, 2'b0} | {FirstK,1'b0} : {3'b1,D,{`DIVb-`DIVN+2{1'b0}}};
// *** |... for continual -1 is not efficent fix - also only needed for radix-2
assign WZeroD = ((WS^WC)=={WS[`DIVb+2:0]|WC[`DIVb+2:0], 1'b0})|(((WS+WC+FZero)==0)&qn[`DIVCOPIES-1]);
assign WZeroD = ((WS^WC)=={WS[`DIVb+2:0]|WC[`DIVb+2:0], 1'b0})|(((WS+WC+FZeroD)==0)&qn[`DIVCOPIES-1]);
end else begin
assign WZeroD = ((WS^WC)=={WS[`DIVb+2:0]|WC[`DIVb+2:0], 1'b0});
end
flopr #(1) WZeroReg(clk, reset | DivStart, WZero, WZeroDelayed);
// assign DivDone = (state == DONE);
// assign DivDone = (state == DONE) | (WZeroD & (state == BUSY));
assign DivDone = (state == DONE) | (WZeroDelayed & (state == BUSY));
assign W = WC+WS;
assign NegSticky = W[`DIVb+3];
@ -123,8 +123,7 @@ module fdivsqrtfsm(
if (StallM) state <= #1 DONE;
else state <= #1 IDLE;
end else if (state == BUSY) begin
// if (step == 1 | WZero ) begin
if (step == 1 /* | WZero */) begin
if (step == 1) begin
state <= #1 DONE;
end
step <= step - 1;

4
pipelined/src/fpu/fdivsqrtstage4.sv
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@ -60,7 +60,7 @@ module fdivsqrtstage4 (
// 0010 = -1
// 0001 = -2
qsel4 qsel4(.D, .WS, .WC, .Sqrt(SqrtM), .q);
// fgen4 fgen4(.s(q), .C, .S, .SM, .F);
fgen4 fgen4(.s(q), .C, .S, .SM, .F);
always_comb
case (q)
@ -78,7 +78,7 @@ module fdivsqrtstage4 (
csa #(`DIVb+4) csa(WS, WC, AddIn, |q[3:2]&~SqrtM, WSA, WCA);
otfc4 otfc4(.q, .Q, .QM, .QNext, .QMNext);
// sotfc4 sotfc4(.s(q), .SqrtM, .C, .S, .SM, .SNext, .SMNext);
sotfc4 sotfc4(.s(q), .SqrtM, .C, .S, .SM, .SNext, .SMNext);
endmodule

77
pipelined/src/fpu/qsel.sv
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@ -111,6 +111,80 @@ module qsel4 (
logic [3:0] QSel4[1023:0];
always_comb begin
integer d, w, i, w2;
for(d=0; d<8; d++)
for(w=0; w<128; w++)begin
i = d*128+w;
w2 = w-128*(w>=64); // convert to two's complement
case(d)
0: if($signed(w2)>=$signed(12)) QSel4[i] = 4'b1000;
else if(w2>=4) QSel4[i] = 4'b0100;
else if(w2>=-4) QSel4[i] = 4'b0000;
else if(w2>=-13) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
1: if(w2>=14) QSel4[i] = 4'b1000;
else if(w2>=4) QSel4[i] = 4'b0100;
else if(w2>=-4) QSel4[i] = 4'b0000;
else if(w2>=-14) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
2: if(w2>=16) QSel4[i] = 4'b1000;
else if(w2>=4) QSel4[i] = 4'b0100;
else if(w2>=-6) QSel4[i] = 4'b0000;
else if(w2>=-16) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
3: if(w2>=16) QSel4[i] = 4'b1000;
else if(w2>=4) QSel4[i] = 4'b0100;
else if(w2>=-6) QSel4[i] = 4'b0000;
else if(w2>=-17) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
4: if(w2>=18) QSel4[i] = 4'b1000;
else if(w2>=6) QSel4[i] = 4'b0100;
else if(w2>=-6) QSel4[i] = 4'b0000;
else if(w2>=-18) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
5: if(w2>=20) QSel4[i] = 4'b1000;
else if(w2>=6) QSel4[i] = 4'b0100;
else if(w2>=-8) QSel4[i] = 4'b0000;
else if(w2>=-20) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
6: if(w2>=20) QSel4[i] = 4'b1000;
else if(w2>=8) QSel4[i] = 4'b0100;
else if(w2>=-8) QSel4[i] = 4'b0000;
else if(w2>=-22) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
7: if(w2>=24) QSel4[i] = 4'b1000;
else if(w2>=8) QSel4[i] = 4'b0100;
else if(w2>=-8) QSel4[i] = 4'b0000;
else if(w2>=-22) QSel4[i] = 4'b0010;
else QSel4[i] = 4'b0001;
endcase
end
end
assign q = QSel4[{Dmsbs,Wmsbs}];
endmodule
// qsel4old was working for divide
module qsel4old (
input logic [`DIVN-2:0] D,
input logic [`DIVb+3:0] WS, WC,
input logic Sqrt,
output logic [3:0] q
);
logic [6:0] Wmsbs;
logic [7:0] PreWmsbs;
logic [2:0] Dmsbs;
assign PreWmsbs = WC[`DIVb+3:`DIVb-4] + WS[`DIVb+3:`DIVb-4];
assign Wmsbs = PreWmsbs[7:1];
assign Dmsbs = D[`DIVN-2:`DIVN-4];//|{3{D[`DIVN-2]&Sqrt}};
// D = 0001.xxx...
// Dmsbs = | |
// W = xxxx.xxx...
// Wmsbs = | |
logic [3:0] QSel4[1023:0];
always_comb begin
integer d, w, i, w2;
for(d=0; d<8; d++)
@ -192,7 +266,4 @@ module fgen4 (
else if (s[1]) F = FN1;
else if (s[0]) F = FN2;
else F = F0;
// assign F = sp ? FP : (sn ? FN : FZ);
endmodule