cmp2lut: new techmap pass.
diff --git a/techlibs/common/Makefile.inc b/techlibs/common/Makefile.inc index 70074f6..0e05620 100644 --- a/techlibs/common/Makefile.inc +++ b/techlibs/common/Makefile.inc
@@ -26,5 +26,5 @@ $(eval $(call add_share_file,share,techlibs/common/adff2dff.v)) $(eval $(call add_share_file,share,techlibs/common/dff2ff.v)) $(eval $(call add_share_file,share,techlibs/common/gate2lut.v)) +$(eval $(call add_share_file,share,techlibs/common/cmp2lut.v)) $(eval $(call add_share_file,share,techlibs/common/cells.lib)) -
diff --git a/techlibs/common/cmp2lut.v b/techlibs/common/cmp2lut.v new file mode 100644 index 0000000..8aa1eb9 --- /dev/null +++ b/techlibs/common/cmp2lut.v
@@ -0,0 +1,105 @@ +// Certain arithmetic operations between a signal of width n and a constant can be directly mapped +// to a single k-LUT (where n <= k). This is preferable to normal alumacc techmapping process +// because for many targets, arithmetic techmapping creates hard logic (such as carry cells) which often +// cannot be optimized further. +// +// TODO: Currently, only comparisons with 1-bit output are mapped. Potentially, all arithmetic cells +// with n <= k inputs should be techmapped in this way, because this shortens the critical path +// from n to 1 by avoiding carry chains. + +(* techmap_celltype = "$eq $ne $lt $le $gt $ge" *) +module _90_lut_cmp_ (A, B, Y); + +parameter A_SIGNED = 0; +parameter B_SIGNED = 0; +parameter A_WIDTH = 0; +parameter B_WIDTH = 0; +parameter Y_WIDTH = 0; + +input [A_WIDTH-1:0] A; +input [B_WIDTH-1:0] B; +output [Y_WIDTH-1:0] Y; + +parameter _TECHMAP_CELLTYPE_ = ""; + +parameter _TECHMAP_CONSTMSK_A_ = 0; +parameter _TECHMAP_CONSTVAL_A_ = 0; +parameter _TECHMAP_CONSTMSK_B_ = 0; +parameter _TECHMAP_CONSTVAL_B_ = 0; + +function automatic integer gen_lut; + input integer width; + input integer operation; + input integer swap; + input integer sign; + input integer operand; + integer n, i_var, i_cst, lhs, rhs, o_bit; + begin + gen_lut = width'b0; + for (n = 0; n < (1 << width); n++) begin + if (sign) + i_var = n[width-1:0]; + else + i_var = n; + i_cst = operand; + if (swap) begin + lhs = i_cst; + rhs = i_var; + end else begin + lhs = i_var; + rhs = i_cst; + end + if (operation == 0) + o_bit = (lhs < rhs); + if (operation == 1) + o_bit = (lhs <= rhs); + if (operation == 2) + o_bit = (lhs > rhs); + if (operation == 3) + o_bit = (lhs >= rhs); + if (operation == 4) + o_bit = (lhs == rhs); + if (operation == 5) + o_bit = (lhs != rhs); + gen_lut = gen_lut | (o_bit << n); + end + end +endfunction + +generate + if (_TECHMAP_CELLTYPE_ == "$lt") + localparam operation = 0; + if (_TECHMAP_CELLTYPE_ == "$le") + localparam operation = 1; + if (_TECHMAP_CELLTYPE_ == "$gt") + localparam operation = 2; + if (_TECHMAP_CELLTYPE_ == "$ge") + localparam operation = 3; + if (_TECHMAP_CELLTYPE_ == "$eq") + localparam operation = 4; + if (_TECHMAP_CELLTYPE_ == "$ne") + localparam operation = 5; + + if (A_WIDTH > `LUT_WIDTH || B_WIDTH > `LUT_WIDTH || Y_WIDTH != 1) + wire _TECHMAP_FAIL_ = 1; + else if (&_TECHMAP_CONSTMSK_B_) + \$lut #( + .WIDTH(A_WIDTH), + .LUT({ gen_lut(A_WIDTH, operation, 0, A_SIGNED && B_SIGNED, _TECHMAP_CONSTVAL_B_) }) + ) _TECHMAP_REPLACE_ ( + .A(A), + .Y(Y) + ); + else if (&_TECHMAP_CONSTMSK_A_) + \$lut #( + .WIDTH(B_WIDTH), + .LUT({ gen_lut(B_WIDTH, operation, 1, A_SIGNED && B_SIGNED, _TECHMAP_CONSTVAL_A_) }) + ) _TECHMAP_REPLACE_ ( + .A(B), + .Y(Y) + ); + else + wire _TECHMAP_FAIL_ = 1; +endgenerate + +endmodule
diff --git a/tests/lut/check_map.ys b/tests/lut/check_map.ys index dc0aaff..46854e8 100644 --- a/tests/lut/check_map.ys +++ b/tests/lut/check_map.ys
@@ -1,4 +1,6 @@ simplemap -equiv_opt -assert techmap -map +/gate2lut.v -D LUT_WIDTH=4 +equiv_opt -assert techmap -D LUT_WIDTH=4 -map +/cmp2lut.v design -load postopt -select -assert-count 1 t:$lut +equiv_opt -assert techmap -D LUT_WIDTH=4 -map +/gate2lut.v +design -load postopt +select -assert-count 0 t:* t:$lut %d
diff --git a/tests/lut/map_cmp.v b/tests/lut/map_cmp.v new file mode 100644 index 0000000..5e413f8 --- /dev/null +++ b/tests/lut/map_cmp.v
@@ -0,0 +1,29 @@ +module top(...); + input [3:0] a; + + output o1_1 = 4'b1010 <= a; + output o1_2 = 4'b1010 < a; + output o1_3 = 4'b1010 >= a; + output o1_4 = 4'b1010 > a; + output o1_5 = 4'b1010 == a; + output o1_6 = 4'b1010 != a; + + output o2_1 = a <= 4'b1010; + output o2_2 = a < 4'b1010; + output o2_3 = a >= 4'b1010; + output o2_4 = a > 4'b1010; + output o2_5 = a == 4'b1010; + output o2_6 = a != 4'b1010; + + output o3_1 = 4'sb0101 <= $signed(a); + output o3_2 = 4'sb0101 < $signed(a); + output o3_3 = 4'sb0101 >= $signed(a); + output o3_4 = 4'sb0101 > $signed(a); + output o3_5 = 4'sb0101 == $signed(a); + output o3_6 = 4'sb0101 != $signed(a); + + output o4_1 = $signed(a) <= 4'sb0000; + output o4_2 = $signed(a) < 4'sb0000; + output o4_3 = $signed(a) >= 4'sb0000; + output o4_4 = $signed(a) > 4'sb0000; +endmodule
diff --git a/tests/lut/run-test.sh b/tests/lut/run-test.sh old mode 100644 new mode 100755