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Add don't care optimisation

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This commit is contained in:
Eddie Hung 2019-05-02 15:01:37 -07:00
parent d80445e049
commit fc72f07efd
1 changed files with 11 additions and 0 deletions
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11
techlibs/xilinx/cells_map.v
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@ -161,11 +161,14 @@ module \$shiftx (A, B, Y);
input [B_WIDTH-1:0] B;
output [Y_WIDTH-1:0] Y;
parameter [A_WIDTH-1:0] _TECHMAP_CONSTMSK_A_ = 0;
parameter [A_WIDTH-1:0] _TECHMAP_CONSTVAL_A_ = 0;
parameter [B_WIDTH-1:0] _TECHMAP_CONSTMSK_B_ = 0;
parameter [B_WIDTH-1:0] _TECHMAP_CONSTVAL_B_ = 0;
generate
genvar i, j;
// TODO: Check if this opt still necessary
if (B_SIGNED) begin
if (_TECHMAP_CONSTMSK_B_[B_WIDTH-1] && _TECHMAP_CONSTVAL_B_[B_WIDTH-1] == 1'b0)
// Optimisation to remove B_SIGNED if sign bit of B is constant-0
@ -186,6 +189,14 @@ module \$shiftx (A, B, Y);
assign A_i[i] = A[i*2];
\$shiftx #(.A_SIGNED(A_SIGNED), .B_SIGNED(B_SIGNED), .A_WIDTH((A_WIDTH+1'd1)/2'd2), .B_WIDTH(B_WIDTH-1'd1), .Y_WIDTH(Y_WIDTH)) _TECHMAP_REPLACE_ (.A(A_i), .B(B[B_WIDTH-1:1]), .Y(Y));
end
// If upper half of A input is all constant 1'bx then
// chop this $shiftx in half
else if (_TECHMAP_CONSTMSK_A_[A_WIDTH-1:2**(B_WIDTH-1)] == {A_WIDTH-2**(B_WIDTH-1){1'b1}} && _TECHMAP_CONSTVAL_A_[A_WIDTH-1:2**(B_WIDTH-1)] === {A_WIDTH-2**(B_WIDTH-1){1'bx}}) begin
if (B_WIDTH > 1)
\$shiftx #(.A_SIGNED(A_SIGNED), .B_SIGNED(B_SIGNED), .A_WIDTH(2**(B_WIDTH-1)), .B_WIDTH(B_WIDTH-1'd1), .Y_WIDTH(Y_WIDTH)) _TECHMAP_REPLACE_ (.A(A[2**(B_WIDTH-1)-1:0]), .B(B[B_WIDTH-2:0]), .Y(Y));
else
assign Y = A[0];
end
else if (B_WIDTH < 3 || A_WIDTH <= 4) begin
wire _TECHMAP_FAIL_ = 1;
end