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zbc and carry-less multiply work properly

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This commit is contained in:
Kevin Kim 2023-02-15 17:37:09 -08:00
parent cf8392cbd8
commit 6ac54a180e
2 changed files with 29 additions and 46 deletions
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41
src/ieu/bmu/clmul.sv
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@ -1,5 +1,5 @@
///////////////////////////////////////////
// clmul.sv
// clmul.sv (carry-less multiplier)
//
// Written: Kevin Kim <kekim@hmc.edu> and Kip Macsai-Goren <kmacsaigoren@hmc.edu>
// Created: 1 February 2023
@ -30,35 +30,24 @@
`include "wally-config.vh"
module clmul #(parameter WIDTH=32) (
input logic [WIDTH-1:0] A, B, // Operands
input logic [WIDTH-1:0] A, B, // Operands
output logic [WIDTH-1:0] ClmulResult); // ZBS result
logic [WIDTH-1:0] pp [WIDTH-1:0]; //partial AND products
// Note: only generates the bottom WIDTH bits of the carryless multiply.
// To get the high bits or the reversed bits, the inputs can be shifted and reversed
// as they are in zbc where this is instantiated
/*
genvar i;
for (i=0; i<WIDTH; i++) begin
assign pp[i] = ((A & {(WIDTH){B[i]}}) << i); // Fill partial product array
// ClmulResult ^= pp[i];
end
assign ClmulResult = pp.xor();
*/
genvar i,j;
for (i=1; i<WIDTH;i++) begin:outer //loop fills partial product array
for (j=0;j<=i;j++) begin:inner
assign pp[i][j] = A[i]&B[j];
logic [(WIDTH*WIDTH)-1:0] s;
logic [WIDTH-1:0] intial;
integer i;
integer j;
always_comb begin
for (i=0;i<WIDTH;i++) begin: outer
s[WIDTH*i]=A[0]&B[i];
for (j=1;j<=i;j++) begin: inner
s[WIDTH*i+j] = (A[j]&B[i-j])^s[WIDTH*i+j-1];
end
ClmulResult[i] = s[WIDTH*i+j-1];
end
end
/*
for (i=1;i<WIDTH;i++) begin:xortree
assign ClmulResult[i] = ^pp[i:0][i];
end
*/
assign ClmulResult[0] = A[0]&B[0];
endmodule

34
src/ieu/bmu/zbc.sv
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@ -36,43 +36,37 @@ module zbc #(parameter WIDTH=32) (
logic [WIDTH-1:0] ClmulResult, RevClmulResult;
logic [WIDTH-1:0] RevA, RevB;
logic [WIDTH-1:0] X,Y;
logic [WIDTH-1:0] x,y;
genvar i;
bitreverse #(WIDTH) brA(.a(A), .b(RevA));
bitreverse #(WIDTH) brB(.a(B), .b(RevB));
bitreverse brA(.a(A), .b(RevA));
bitreverse brB(.a(B), .b(RevB));
//NOTE: Is it better to mux in input to a SINGLE clmul or to instantiate 3 clmul and MUX the result?
//current implementation CP goes MUX -> CLMUL -> MUX -> RESULT
//alternate could have CLMUL * 3 -> MUX -> MUX
always_comb begin
casez (Funct3)
3'b001: begin //clmul
X = A;
Y = B;
x = A;
y = B;
end
3'b011: begin //clmulh
X = {RevA[WIDTH-2:0], {1'b0}};
Y = {{1'b0}, RevB[WIDTH-2:0]};
x = {RevA[WIDTH-2:0], {1'b0}};
y = {{1'b0}, RevB[WIDTH-2:0]};
end
3'b010: begin //clmulr
X = {A[WIDTH-2:0], {1'b0}};
Y = B;
x = RevA;
y = RevB;
end
default: begin
X = 0;
Y = 0;
x = 0;
y = 0;
end
endcase
end
clmul clm(.A(X), .B(Y), .ClmulResult(ClmulResult));
bitreverse brClmulResult(.a(ClmulResult), .b(RevClmulResult));
clmul #(WIDTH) clm(.A(x), .B(y), .ClmulResult(ClmulResult));
bitreverse #(WIDTH) brClmulResult(.a(ClmulResult), .b(RevClmulResult));
assign ZBCResult = (Funct3 == 3'b011) ? RevClmulResult : ClmulResult;
assign ZBCResult = (Funct3 == 3'b011 || Funct3 == 3'b010) ? RevClmulResult : ClmulResult;
endmodule