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synth_intel_alm: alternative synthesis for Intel FPGAs

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By operating at a layer of abstraction over the rather clumsy Intel primitives,
we can avoid special hacks like `dffinit -highlow` in favour of simple techmapping.

This also makes the primitives much easier to manipulate, and more descriptive
(no more cyclonev_lcell_comb to mean anything from a LUT2 to a LUT6).
This commit is contained in:
Dan Ravensloft 2019-11-19 10:19:00 +00:00 • committed by Marcelina Kościelnicka
parent 4c52691a58
commit 2e37e62e6b
29 changed files with 1662 additions and 1 deletions
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64
techlibs/intel_alm/common/arith_alm_map.v Normal file
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`default_nettype none
module \$alu (A, B, CI, BI, X, Y, CO);
parameter A_SIGNED = 0;
parameter B_SIGNED = 0;
parameter A_WIDTH = 1;
parameter B_WIDTH = 1;
parameter Y_WIDTH = 1;
parameter _TECHMAP_CONSTMSK_CI_ = 0;
parameter _TECHMAP_CONSTVAL_CI_ = 0;
input [A_WIDTH-1:0] A;
input [B_WIDTH-1:0] B;
input CI, BI;
output [Y_WIDTH-1:0] X, Y, CO;
wire [Y_WIDTH-1:0] A_buf, B_buf;
\$pos #(.A_SIGNED(A_SIGNED), .A_WIDTH(A_WIDTH), .Y_WIDTH(Y_WIDTH)) A_conv (.A(A), .Y(A_buf));
\$pos #(.A_SIGNED(B_SIGNED), .A_WIDTH(B_WIDTH), .Y_WIDTH(Y_WIDTH)) B_conv (.A(B), .Y(B_buf));
wire [Y_WIDTH-1:0] AA = A_buf;
wire [Y_WIDTH-1:0] BB = BI ? ~B_buf : B_buf;
wire [Y_WIDTH-1:0] BX = B_buf;
wire [Y_WIDTH:0] ALM_CARRY;
// Start of carry chain
generate
if (_TECHMAP_CONSTMSK_CI_ == 1) begin
assign ALM_CARRY[0] = _TECHMAP_CONSTVAL_CI_;
end else begin
MISTRAL_ALUT_ARITH #(
.LUT0(16'b1010_1010_1010_1010), // Q = A
.LUT1(16'b0000_0000_0000_0000), // Q = 0 (LUT1's input to the adder is inverted)
) alm_start (
.A(CI), .B(1'b1), .C(1'b1), .D0(1'b1), .D1(1'b1),
.CI(1'b0),
.CO(ALM_CARRY[0])
);
end
endgenerate
// Carry chain
genvar i;
generate for (i = 0; i < Y_WIDTH; i = i + 1) begin:slice
// TODO: mwk suggests that a pass could merge pre-adder logic into this.
MISTRAL_ALUT_ARITH #(
.LUT0(16'b1010_1010_1010_1010), // Q = A
.LUT1(16'b1100_0011_1100_0011), // Q = C ? B : ~B (LUT1's input to the adder is inverted)
) alm_i (
.A(AA[i]), .B(BX[i]), .C(BI), .D0(1'b1), .D1(1'b1),
.CI(ALM_CARRY[i]),
.SO(Y[i]),
.CO(ALM_CARRY[i+1])
);
// ALM carry chain is not directly accessible, so calculate the carry through soft logic if really needed.
assign CO[i] = (AA[i] && BB[i]) || ((Y[i] ^ AA[i] ^ BB[i]) && (AA[i] || BB[i]));
end endgenerate
assign X = AA ^ BB;
endmodule