diff --git a/pipelined/src/ieu/comparator.sv b/pipelined/src/ieu/comparator.sv index b871e7b36..eacc8723e 100644 --- a/pipelined/src/ieu/comparator.sv +++ b/pipelined/src/ieu/comparator.sv @@ -47,277 +47,3 @@ module comparator_dc_flip #(parameter WIDTH=64) ( assign lt = (af < bf); // lt = 1 when a less than b (taking signed operands into account) assign flags = {eq, lt}; endmodule - -/* - -Other comparators evaluated: - -module donedet #(parameter WIDTH=64) ( - input logic [WIDTH-1:0] a, b, - output logic eq); - - //assign eq = (a+b == 0); // gives good speed but 3x necessary area - // See CMOS VLSI Design 4th Ed. p. 463 K = A+B for K = 0 - assign eq = ((a ^ b) == {a[WIDTH-2:0], 1'b0} | {b[WIDTH-2:0], 1'b0}); - endmodule - -module comparator_sub #(parameter WIDTH=64) ( - input logic [WIDTH-1:0] a, b, - output logic [2:0] flags); - - logic eq, lt, ltu; - - - // Subtractor implementation - logic [WIDTH-1:0] bbar, diff; - logic carry, neg, overflow; - - // subtraction - assign bbar = ~b; - assign {carry, diff} = a + bbar + 1; - - // condition code flags based on add/subtract output - assign eq = (diff == 0); - assign neg = diff[WIDTH-1]; - // overflow occurs when the numbers being subtracted have the opposite sign - // and the result has the opposite sign fron the first - assign overflow = (a[WIDTH-1] ^ b[WIDTH-1]) & (a[WIDTH-1] ^ diff[WIDTH-1]); - assign lt = neg ^ overflow; - assign ltu = ~carry; - assign flags = {eq, lt, ltu}; -endmodule - -// comparator_flip, gives slightly better synthesis -module comparator #(parameter WIDTH=64) ( - input logic [WIDTH-1:0] a, b, - output logic [2:0] flags); - - logic eq, lt, ltu; - - // Behavioral description gives best results - assign eq = (a == b); - assign ltu = (a < b); - assign lt = ($signed(a) < $signed(b)); - - assign flags = {eq, lt, ltu}; -endmodule - - -module comparator2 #(parameter WIDTH=64) ( - input logic [WIDTH-1:0] a, b, - output logic [2:0] flags); - - logic eq, lt, ltu; - - /* verilator lint_off UNOPTFLAT / - // prefix implementation - localparam levels=$clog2(WIDTH); - genvar i; - genvar level; - logic [WIDTH-1:0] e[levels:0]; - logic [WIDTH-1:0] l[levels:0]; - logic eq2, lt2, ltu2; - - // Bitwise logic - assign e[0] = a ~^ b; // bitwise equality - assign l[0] = ~a & b; // bitwise less than unsigned: A=0 and B=1 - - // Recursion - for (level = 1; level<=levels; level++) begin - for (i=0; i B using a minimized sum-of-products expression - assign GT = A[1]&~B[1] | A[1]&A[0]&~B[0] | A[0]&~B[1]&~B[0]; - -endmodule // magcompare2b - -// 2-bit magnitude comparator -// This module compares two 2-bit values A and B. LT is '1' if A < B -// and GT is '1'if A > B. LT and GT are both '0' if A = B. However, -// this version actually incorporates don't cares into the equation to -// simplify the optimization - -module magcompare2c (LT, GT, A, B); - - input logic [1:0] A; - input logic [1:0] B; - - output logic LT; - output logic GT; - - assign LT = B[1] | (!A[1]&B[0]); - assign GT = A[1] | (!B[1]&A[0]); - -endmodule // magcompare2b - -// This module compares two 64-bit values A and B. LT is '1' if A < B -// and EQ is '1'if A = B. LT and GT are both '0' if A > B. -// This structure was modified so -// that it only does a strict magnitdude comparison, and only -// returns flags for less than (LT) and eqaual to (EQ). It uses a tree -// of 63 2-bit magnitude comparators, followed by one OR gates. -// - -module stinecomp64 (FCC, A, B, Sel); - - input logic [63:0] A; - input logic [63:0] B; - input logic Sel; - - output logic [1:0] FCC; - - logic [31:0] s; - logic [31:0] t; - logic [15:0] u; - logic [15:0] v; - logic [7:0] w; - logic [7:0] x; - logic [3:0] y; - logic [3:0] z; - logic [1:0] a; - logic [1:0] b; - logic GT; - logic LT; - logic EQ; - logic [1:0] A2; - logic [1:0] B2; - - assign A2 = Sel ? {~A[63], A[62]} : A[63:62]; - assign B2 = Sel ? {~B[63], B[62]} : B[63:62]; - - magcompare2b mag1(s[0], t[0], A[1:0], B[1:0]); - magcompare2b mag2(s[1], t[1], A[3:2], B[3:2]); - magcompare2b mag3(s[2], t[2], A[5:4], B[5:4]); - magcompare2b mag4(s[3], t[3], A[7:6], B[7:6]); - magcompare2b mag5(s[4], t[4], A[9:8], B[9:8]); - magcompare2b mag6(s[5], t[5], A[11:10], B[11:10]); - magcompare2b mag7(s[6], t[6], A[13:12], B[13:12]); - magcompare2b mag8(s[7], t[7], A[15:14], B[15:14]); - magcompare2b mag9(s[8], t[8], A[17:16], B[17:16]); - magcompare2b magA(s[9], t[9], A[19:18], B[19:18]); - magcompare2b magB(s[10], t[10], A[21:20], B[21:20]); - magcompare2b magC(s[11], t[11], A[23:22], B[23:22]); - magcompare2b magD(s[12], t[12], A[25:24], B[25:24]); - magcompare2b magE(s[13], t[13], A[27:26], B[27:26]); - magcompare2b magF(s[14], t[14], A[29:28], B[29:28]); - magcompare2b mag10(s[15], t[15], A[31:30], B[31:30]); - magcompare2b mag11(s[16], t[16], A[33:32], B[33:32]); - magcompare2b mag12(s[17], t[17], A[35:34], B[35:34]); - magcompare2b mag13(s[18], t[18], A[37:36], B[37:36]); - magcompare2b mag14(s[19], t[19], A[39:38], B[39:38]); - magcompare2b mag15(s[20], t[20], A[41:40], B[41:40]); - magcompare2b mag16(s[21], t[21], A[43:42], B[43:42]); - magcompare2b mag17(s[22], t[22], A[45:44], B[45:44]); - magcompare2b mag18(s[23], t[23], A[47:46], B[47:46]); - magcompare2b mag19(s[24], t[24], A[49:48], B[49:48]); - magcompare2b mag1A(s[25], t[25], A[51:50], B[51:50]); - magcompare2b mag1B(s[26], t[26], A[53:52], B[53:52]); - magcompare2b mag1C(s[27], t[27], A[55:54], B[55:54]); - magcompare2b mag1D(s[28], t[28], A[57:56], B[57:56]); - magcompare2b mag1E(s[29], t[29], A[59:58], B[59:58]); - magcompare2b mag1F(s[30], t[30], A[61:60], B[61:60]); - magcompare2b mag20(s[31], t[31], A2, B2); - - magcompare2c mag21(u[0], v[0], t[1:0], s[1:0]); - magcompare2c mag22(u[1], v[1], t[3:2], s[3:2]); - magcompare2c mag23(u[2], v[2], t[5:4], s[5:4]); - magcompare2c mag24(u[3], v[3], t[7:6], s[7:6]); - magcompare2c mag25(u[4], v[4], t[9:8], s[9:8]); - magcompare2c mag26(u[5], v[5], t[11:10], s[11:10]); - magcompare2c mag27(u[6], v[6], t[13:12], s[13:12]); - magcompare2c mag28(u[7], v[7], t[15:14], s[15:14]); - magcompare2c mag29(u[8], v[8], t[17:16], s[17:16]); - magcompare2c mag2A(u[9], v[9], t[19:18], s[19:18]); - magcompare2c mag2B(u[10], v[10], t[21:20], s[21:20]); - magcompare2c mag2C(u[11], v[11], t[23:22], s[23:22]); - magcompare2c mag2D(u[12], v[12], t[25:24], s[25:24]); - magcompare2c mag2E(u[13], v[13], t[27:26], s[27:26]); - magcompare2c mag2F(u[14], v[14], t[29:28], s[29:28]); - magcompare2c mag30(u[15], v[15], t[31:30], s[31:30]); - - magcompare2c mag31(w[0], x[0], v[1:0], u[1:0]); - magcompare2c mag32(w[1], x[1], v[3:2], u[3:2]); - magcompare2c mag33(w[2], x[2], v[5:4], u[5:4]); - magcompare2c mag34(w[3], x[3], v[7:6], u[7:6]); - magcompare2c mag35(w[4], x[4], v[9:8], u[9:8]); - magcompare2c mag36(w[5], x[5], v[11:10], u[11:10]); - magcompare2c mag37(w[6], x[6], v[13:12], u[13:12]); - magcompare2c mag38(w[7], x[7], v[15:14], u[15:14]); - - magcompare2c mag39(y[0], z[0], x[1:0], w[1:0]); - magcompare2c mag3A(y[1], z[1], x[3:2], w[3:2]); - magcompare2c mag3B(y[2], z[2], x[5:4], w[5:4]); - magcompare2c mag3C(y[3], z[3], x[7:6], w[7:6]); - - magcompare2c mag3D(a[0], b[0], z[1:0], y[1:0]); - magcompare2c mag3E(a[1], b[1], z[3:2], y[3:2]); - - magcompare2c mag3F(LT, GT, b[1:0], a[1:0]); - - assign EQ = ~(LT | GT); - assign FCC = {LT, EQ}; - -endmodule // comp64 -*/ \ No newline at end of file