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Add support for variable length Xilinx SRL > 128

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This commit is contained in:
Eddie Hung 2019-03-19 17:44:33 -07:00
parent ae2a625d05
commit 5445cd4d00
2 changed files with 68 additions and 18 deletions
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6
passes/techmap/shregmap.cc
View file

@ -165,12 +165,6 @@ struct ShregmapTechXilinx7 : ShregmapTech
}
log_assert(shiftx);
// Cannot implement variable-length shift registers
// greater than 128 since Q31 cannot be output onto
// fabric
if (GetSize(taps) > 128)
return false;
// Only map if $shiftx exclusively covers the shift register
if (GetSize(taps) != shiftx->getParam("\\A_WIDTH").as_int())
return false;

80
techlibs/xilinx/cells_map.v
View file

@ -105,23 +105,79 @@ module \$__SHREG_ (input C, input D, input [31:0] L, input E, output Q);
end
else begin
// For variable length, bump up to the next length
// because we can't access Q31
\$__SHREG_ #(.DEPTH(DEPTH+1), .INIT({INIT,1'b0}), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) _TECHMAP_REPLACE_ (.C(C), .D(D), .L(L), .E(E), .Q(Q));
end
end
else begin
if (&_TECHMAP_CONSTMSK_L_) begin
// UG474 (v1.8, p34) states that:
// "There are no direct connections between slices to form longer shift
// registers, nor is the MC31 output at LUT B/C/D available."
wire T0;
\$__SHREG_ #(.DEPTH(128), .INIT(INIT[DEPTH-1:DEPTH-128]), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) fpga_srl_0 (.C(C), .D(D), .L(127), .E(E), .Q(T0));
\$__SHREG_ #(.DEPTH(DEPTH-128), .INIT(INIT[DEPTH-128-1:0]), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) fpga_srl_1 (.C(C), .D(T0), .L(DEPTH-1-128), .E(E), .Q(Q));
end
\$__XILINX_SHREG_ #(.DEPTH(DEPTH), .INIT(INIT), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) _TECHMAP_REPLACE_ (.C(C), .D(D), .L(L), .E(E), .Q(Q));
end
endgenerate
endmodule
module \$__XILINX_SHREG_ (input C, input D, input [31:0] L, input E, output Q, output SO);
parameter DEPTH = 0;
parameter [DEPTH-1:0] INIT = 0;
parameter CLKPOL = 1;
parameter ENPOL = 2;
// shregmap's INIT parameter shifts out LSB first;
// however Xilinx expects MSB first
function [DEPTH-1:0] brev;
input [DEPTH-1:0] din;
integer i;
begin
for (i = 0; i < DEPTH; i=i+1)
brev[i] = din[DEPTH-1-i];
end
endfunction
localparam [DEPTH-1:0] INIT_R = brev(INIT);
parameter _TECHMAP_CONSTMSK_L_ = 0;
parameter _TECHMAP_CONSTVAL_L_ = 0;
generate
if (DEPTH == 1) begin
\$__SHREG_ #(.DEPTH(DEPTH), .INIT(INIT), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) _TECHMAP_REPLACE_ (.C(C), .D(D), .L(0), .E(E), .Q(Q));
end
else if (DEPTH < 128) begin
\$__SHREG_ #(.DEPTH(DEPTH), .INIT(INIT), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) _TECHMAP_REPLACE_ (.C(C), .D(D), .L(L), .E(E), .Q(Q));
end
else if (DEPTH == 128) begin
wire CE;
if (ENPOL == 0)
assign CE = ~E;
else if (ENPOL == 1)
assign CE = E;
else
assign CE = 1'b1;
wire T0, T1, T2, T3, T4, T5, T6;
SRLC32E #(.INIT(INIT_R[32-1:0]), .IS_CLK_INVERTED(~CLKPOL[0])) fpga_srl_0 (.A(L[4:0]), .CE(CE), .CLK(C), .D(D), .Q(T0), .Q31(T1));
SRLC32E #(.INIT(INIT_R[64-1:32]), .IS_CLK_INVERTED(~CLKPOL[0])) fpga_srl_1 (.A(L[4:0]), .CE(CE), .CLK(C), .D(T1), .Q(T2), .Q31(T3));
SRLC32E #(.INIT(INIT_R[96-1:64]), .IS_CLK_INVERTED(~CLKPOL[0])) fpga_srl_2 (.A(L[4:0]), .CE(CE), .CLK(C), .D(T3), .Q(T4), .Q31(T5));
SRLC32E #(.INIT(INIT_R[128-1:96]), .IS_CLK_INVERTED(~CLKPOL[0])) fpga_srl_3 (.A(L[4:0]), .CE(CE), .CLK(C), .D(T5), .Q(T6), .Q31(SO));
if (&_TECHMAP_CONSTMSK_L_)
assign Q = T6;
else begin
// No way to create variable length shift registers >128 bits as Q31
// cannot be output to the fabric...
wire _TECHMAP_FAIL_ = 1;
wire T7, T8;
MUXF7 fpga_mux_0 (.O(T7), .I0(T0), .I1(T2), .S(L[5]));
MUXF7 fpga_mux_1 (.O(T8), .I0(T4), .I1(T6), .S(L[5]));
MUXF8 fpga_mux_2 (.O(Q), .I0(T7), .I1(T8), .S(L[6]));
end
end
else if (DEPTH > 128) begin
localparam lower_clog2 = $clog2((DEPTH+1)/2);
localparam lower_depth = 2 ** lower_clog2;
wire T0, T1, T2;
\$__XILINX_SHREG_ #(.DEPTH(lower_depth), .INIT(INIT[DEPTH-1:DEPTH-lower_depth]), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) fpga_srl_0 (.C(C), .D(D), .L(L[lower_clog2-1:0]), .E(E), .Q(T0), .SO(T1));
\$__XILINX_SHREG_ #(.DEPTH(DEPTH-lower_depth), .INIT(INIT[DEPTH-lower_depth-1:0]), .CLKPOL(CLKPOL), .ENPOL(ENPOL)) fpga_srl_1 (.C(C), .D(T1), .L(L[lower_clog2-1:0]), .E(E), .Q(T2));
if (&_TECHMAP_CONSTMSK_L_)
assign Q = T2;
else begin
//assign Q = L[lower_clog2-1] ? T2 : T0;
// FIXME: Need to instantiate 2:1 MUX here since
// techmap with this file is run AFTER abc
LUT3 #(.INIT(8'b10101100)) fpga_mux (.I0(T2), .I1(T0), .I2(L[lower_clog2]), .O(Q));
end
end
endgenerate