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New techmap +/shiftx2mux.v which decomposes LSB first; better for ABC

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Eddie Hung 2020-01-16 15:25:49 -08:00
parent f165a74824
commit 7977574995
3 changed files with 149 additions and 0 deletions
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1
techlibs/common/Makefile.inc
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@ -30,3 +30,4 @@ $(eval $(call add_share_file,share,techlibs/common/cmp2lut.v))
$(eval $(call add_share_file,share,techlibs/common/cells.lib))
$(eval $(call add_share_file,share,techlibs/common/mul2dsp.v))
$(eval $(call add_share_file,share,techlibs/common/dummy.box))
$(eval $(call add_share_file,share,techlibs/common/shiftx2mux.v))

38
techlibs/common/shiftx2mux.v Normal file
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@ -0,0 +1,38 @@
(* techmap_celltype = /*"$shift*/ "$shiftx" *)
module _80_shift_shiftx (A, B, Y);
parameter A_SIGNED = 0;
parameter B_SIGNED = 0;
parameter A_WIDTH = 1;
parameter B_WIDTH = 1;
parameter Y_WIDTH = 1;
input [A_WIDTH-1:0] A;
input [B_WIDTH-1:0] B;
output [Y_WIDTH-1:0] Y;
parameter [B_WIDTH-1:0] _TECHMAP_CONSTMSK_B_ = 0;
parameter [B_WIDTH-1:0] _TECHMAP_CONSTVAL_B_ = 0;
generate
genvar i;
localparam CLOG2_Y_WIDTH = $clog2(Y_WIDTH);
if (B_WIDTH <= CLOG2_Y_WIDTH+1)
wire _TECHMAP_FAIL_ = 1;
// In order to perform this optimisation, this $shiftx must
// only shift in units of Y_WIDTH, which we check by ensuring
// that the appropriate LSBs of B are zero
else if (_TECHMAP_CONSTMSK_B_[CLOG2_Y_WIDTH-1:0] == {CLOG2_Y_WIDTH{1'b1}} && _TECHMAP_CONSTVAL_B_[CLOG2_Y_WIDTH-1:0] != {CLOG2_Y_WIDTH{1'b0}})
wire _TECHMAP_FAIL_ = 1;
else begin
// Halve the size of $shiftx by $mux-ing A according to
// the LSB of B, after discarding the zeroed bits
wire [(A_WIDTH+Y_WIDTH)/2-1:0] AA;
for (i = 0; i < (A_WIDTH/Y_WIDTH); i=i+2)
assign AA[(i/2)*Y_WIDTH +: Y_WIDTH] = B[CLOG2_Y_WIDTH] ? A[(i+1)*Y_WIDTH +: Y_WIDTH] : A[(i+0)*Y_WIDTH +: Y_WIDTH];
$shiftx #(.A_SIGNED(A_SIGNED), .B_SIGNED(B_SIGNED), .A_WIDTH((A_WIDTH+Y_WIDTH)/2'd2), .B_WIDTH(B_WIDTH-1), .Y_WIDTH(Y_WIDTH)) _TECHMAP_REPLACE_ (.A(AA), .B({B[B_WIDTH-1:CLOG2_Y_WIDTH+1], {CLOG2_Y_WIDTH{1'b0}}}), .Y(Y));
end
endgenerate
endmodule