Merge remote-tracking branch 'origin/master' into xaig_dff

14 files changed, 995 insertions, 81 deletions

diff --git a/techlibs/ecp5/cells_map.v b/techlibs/ecp5/cells_map.v
index 71ae9237b..10e89a3e0 100644
--- a/techlibs/ecp5/cells_map.v
+++ b/techlibs/ecp5/cells_map.v
@@ -47,6 +47,21 @@ module  \$__DFFSE_NP1 (input D, C, E, R, output Q); TRELLIS_FF #(.GSR("AUTO"), .
 module  \$__DFFSE_PP0 (input D, C, E, R, output Q); TRELLIS_FF #(.GSR("AUTO"), .CEMUX("CE"), .CLKMUX("CLK"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("LSR_OVER_CE"))  _TECHMAP_REPLACE_ (.CLK(C), .CE(E), .LSR(R), .DI(D), .Q(Q)); endmodule
 module  \$__DFFSE_PP1 (input D, C, E, R, output Q); TRELLIS_FF #(.GSR("AUTO"), .CEMUX("CE"), .CLKMUX("CLK"), .LSRMUX("LSR"), .REGSET("SET"), .SRMODE("LSR_OVER_CE"))  _TECHMAP_REPLACE_ (.CLK(C), .CE(E), .LSR(R), .DI(D), .Q(Q)); endmodule
 
+`ifdef ASYNC_PRLD
+module  \$_DLATCH_N_ (input E, input D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.LSR(!E), .DI(1'b0), .M(D), .Q(Q)); endmodule
+module  \$_DLATCH_P_ (input E, input D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.LSR(E), .DI(1'b0), .M(D), .Q(Q)); endmodule
+
+module \$_DFFSR_NNN_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("INV"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(!S || !R), .DI(D), .M(R), .Q(Q)); endmodule
+module \$_DFFSR_NNP_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("INV"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(!S || R), .DI(D), .M(!R), .Q(Q)); endmodule
+module \$_DFFSR_NPN_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("INV"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(S || !R), .DI(D), .M(R), .Q(Q)); endmodule
+module \$_DFFSR_NPP_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("INV"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(S || R), .DI(D), .M(!R), .Q(Q)); endmodule
+
+module \$_DFFSR_PNN_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("CLK"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(!S || !R), .DI(D), .M(R), .Q(Q)); endmodule
+module \$_DFFSR_PNP_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("CLK"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(!S || R), .DI(D), .M(!R), .Q(Q)); endmodule
+module \$_DFFSR_PPN_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("CLK"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(S || !R), .DI(D), .M(R), .Q(Q)); endmodule
+module \$_DFFSR_PPP_ (input C, S, R, D, output Q); TRELLIS_FF #(.GSR("DISABLED"), .CEMUX("1"), .CLKMUX("CLK"), .LSRMODE("PRLD"), .LSRMUX("LSR"), .REGSET("RESET"), .SRMODE("ASYNC"))  _TECHMAP_REPLACE_ (.CLK(C), .LSR(S || R), .DI(D), .M(!R), .Q(Q)); endmodule
+`endif
+
 `include "cells_ff.vh"
 `include "cells_io.vh"
 
diff --git a/techlibs/ecp5/synth_ecp5.cc b/techlibs/ecp5/synth_ecp5.cc
index 4cbb56ea1..b71bb2395 100644
--- a/techlibs/ecp5/synth_ecp5.cc
+++ b/techlibs/ecp5/synth_ecp5.cc
@@ -79,6 +79,9 @@ struct SynthEcp5Pass : public ScriptPass
 		log("    -nowidelut\n");
 		log("        do not use PFU muxes to implement LUTs larger than LUT4s\n");
 		log("\n");
+		log("    -asyncprld\n");
+		log("        use async PRLD mode to implement DLATCH and DFFSR (EXPERIMENTAL)\n");
+		log("\n");
 		log("    -abc2\n");
 		log("        run two passes of 'abc' for slightly improved logic density\n");
 		log("\n");
@@ -99,7 +102,7 @@ struct SynthEcp5Pass : public ScriptPass
 	}
 
 	string top_opt, blif_file, edif_file, json_file;
-	bool noccu2, nodffe, nobram, nolutram, nowidelut, flatten, retime, abc2, abc9, nodsp, vpr;
+	bool noccu2, nodffe, nobram, nolutram, nowidelut, asyncprld, flatten, retime, abc2, abc9, nodsp, vpr;
 
 	void clear_flags() YS_OVERRIDE
 	{
@@ -112,6 +115,7 @@ struct SynthEcp5Pass : public ScriptPass
 		nobram = false;
 		nolutram = false;
 		nowidelut = false;
+		asyncprld = false;
 		flatten = true;
 		retime = false;
 		abc2 = false;
@@ -176,6 +180,10 @@ struct SynthEcp5Pass : public ScriptPass
 				nobram = true;
 				continue;
 			}
+			if (args[argidx] == "-asyncprld") {
+				asyncprld = true;
+				continue;
+			}
 			if (args[argidx] == "-nolutram" || /*deprecated alias*/ args[argidx] == "-nodram") {
 				nolutram = true;
 				continue;
@@ -292,7 +300,7 @@ struct SynthEcp5Pass : public ScriptPass
 			run("opt_clean");
 			if (!nodffe)
 				run("dff2dffe -direct-match $_DFF_* -direct-match $__DFFS_*");
-			run("techmap -D NO_LUT -map +/ecp5/cells_map.v");
+			run(stringf("techmap -D NO_LUT %s -map +/ecp5/cells_map.v", help_mode ? "[-D ASYNC_PRLD]" : (asyncprld ? "-D ASYNC_PRLD" : "")));
 			run("opt_expr -undriven -mux_undef");
 			run("simplemap");
 			run("ecp5_ffinit");
@@ -306,10 +314,11 @@ struct SynthEcp5Pass : public ScriptPass
 			if (abc2 || help_mode) {
 				run("abc", "      (only if -abc2)");
 			}
-			std::string techmap_args = "-map +/ecp5/latches_map.v";
+			std::string techmap_args = asyncprld ? "" : "-map +/ecp5/latches_map.v";
 			if (abc9)
 				techmap_args += " -map +/ecp5/abc9_map.v -max_iter 1";
-			run("techmap " + techmap_args);
+			if (!asyncprld || abc9)
+				run("techmap " + techmap_args);
 
 			if (abc9) {
 				run("read_verilog -icells -lib +/ecp5/abc9_model.v");
diff --git a/techlibs/xilinx/Makefile.inc b/techlibs/xilinx/Makefile.inc
index 3ebc72fe8..3f2fbcc85 100644
--- a/techlibs/xilinx/Makefile.inc
+++ b/techlibs/xilinx/Makefile.inc
@@ -1,5 +1,6 @@
 
 OBJS += techlibs/xilinx/synth_xilinx.o
+OBJS += techlibs/xilinx/xilinx_dffopt.o
 
 GENFILES += techlibs/xilinx/brams_init_36.vh
 GENFILES += techlibs/xilinx/brams_init_32.vh
diff --git a/techlibs/xilinx/cells_map.v b/techlibs/xilinx/cells_map.v
index de2068bc5..cc180f2b9 100644
--- a/techlibs/xilinx/cells_map.v
+++ b/techlibs/xilinx/cells_map.v
@@ -28,6 +28,33 @@ module _90_dff_nn1_to_np1 (input D, C, R, output Q); \$_DFF_NP1_   _TECHMAP_REPL
 (* techmap_celltype = "$_DFF_PN1_" *)
 module _90_dff_pn1_to_pp1 (input D, C, R, output Q); \$_DFF_PP1_   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R)); endmodule
 
+(* techmap_celltype = "$__DFFE_NN0" *)
+module _90_dffe_nn0_to_np0 (input D, C, R, E, output Q); \$__DFFE_NP0  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+(* techmap_celltype = "$__DFFE_PN0" *)
+module _90_dffe_pn0_to_pp0 (input D, C, R, E, output Q); \$__DFFE_PP0  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+(* techmap_celltype = "$__DFFE_NN1" *)
+module _90_dffe_nn1_to_np1 (input D, C, R, E, output Q); \$__DFFE_NP1   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+(* techmap_celltype = "$__DFFE_PN1" *)
+module _90_dffe_pn1_to_pp1 (input D, C, R, E, output Q); \$__DFFE_PP1   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+
+(* techmap_celltype = "$__DFFS_NN0_" *)
+module _90_dffs_nn0_to_np0 (input D, C, R, output Q); \$__DFFS_NP0_  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R)); endmodule
+(* techmap_celltype = "$__DFFS_PN0_" *)
+module _90_dffs_pn0_to_pp0 (input D, C, R, output Q); \$__DFFS_PP0_  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R)); endmodule
+(* techmap_celltype = "$__DFFS_NN1_" *)
+module _90_dffs_nn1_to_np1 (input D, C, R, output Q); \$__DFFS_NP1_   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R)); endmodule
+(* techmap_celltype = "$__DFFS_PN1_" *)
+module _90_dffs_pn1_to_pp1 (input D, C, R, output Q); \$__DFFS_PP1_   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R)); endmodule
+
+(* techmap_celltype = "$__DFFSE_NN0" *)
+module _90_dffse_nn0_to_np0 (input D, C, R, E, output Q); \$__DFFSE_NP0  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+(* techmap_celltype = "$__DFFSE_PN0" *)
+module _90_dffse_pn0_to_pp0 (input D, C, R, E, output Q); \$__DFFSE_PP0  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+(* techmap_celltype = "$__DFFSE_NN1" *)
+module _90_dffse_nn1_to_np1 (input D, C, R, E, output Q); \$__DFFSE_NP1   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+(* techmap_celltype = "$__DFFSE_PN1" *)
+module _90_dffse_pn1_to_pp1 (input D, C, R, E, output Q); \$__DFFSE_PP1   _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .R(~R), .E(E)); endmodule
+
 module \$__SHREG_ (input C, input D, input E, output Q);
   parameter DEPTH = 0;
   parameter [DEPTH-1:0] INIT = 0;
diff --git a/techlibs/xilinx/cells_sim.v b/techlibs/xilinx/cells_sim.v
index ef963793c..7941a94cd 100644
--- a/techlibs/xilinx/cells_sim.v
+++ b/techlibs/xilinx/cells_sim.v
@@ -320,6 +320,41 @@ module FDRE_1 (
   always @(negedge C) if (R) Q <= 1'b0; else if (CE) Q <= D;
 endmodule
 
+module FDRSE (
+  output reg Q,
+  (* clkbuf_sink *)
+  (* invertible_pin = "IS_C_INVERTED" *)
+  input C,
+  (* invertible_pin = "IS_CE_INVERTED" *)
+  input CE,
+  (* invertible_pin = "IS_D_INVERTED" *)
+  input D,
+  (* invertible_pin = "IS_R_INVERTED" *)
+  input R,
+  (* invertible_pin = "IS_S_INVERTED" *)
+  input S
+);
+  parameter [0:0] INIT = 1'b0;
+  parameter [0:0] IS_C_INVERTED = 1'b0;
+  parameter [0:0] IS_CE_INVERTED = 1'b0;
+  parameter [0:0] IS_D_INVERTED = 1'b0;
+  parameter [0:0] IS_R_INVERTED = 1'b0;
+  parameter [0:0] IS_S_INVERTED = 1'b0;
+  initial Q <= INIT;
+  wire c = C ^ IS_C_INVERTED;
+  wire ce = CE ^ IS_CE_INVERTED;
+  wire d = D ^ IS_D_INVERTED;
+  wire r = R ^ IS_R_INVERTED;
+  wire s = S ^ IS_S_INVERTED;
+  always @(posedge c)
+    if (r)
+      Q <= 0;
+    else if (s)
+      Q <= 1;
+    else if (ce)
+      Q <= d;
+endmodule
+
 (* abc9_box_id=1003, lib_whitebox, abc9_flop *)
 module FDCE (
   (* abc9_arrival=303 *)
@@ -1193,10 +1228,10 @@ module RAM64M (
   output DOB,
   output DOC,
   output DOD,
-  input [4:0] ADDRA,
-  input [4:0] ADDRB,
-  input [4:0] ADDRC,
-  input [4:0] ADDRD,
+  input [5:0] ADDRA,
+  input [5:0] ADDRB,
+  input [5:0] ADDRC,
+  input [5:0] ADDRD,
   input DIA,
   input DIB,
   input DIC,
@@ -1238,14 +1273,14 @@ module RAM64M8 (
   output DOF,
   output DOG,
   output DOH,
-  input [4:0] ADDRA,
-  input [4:0] ADDRB,
-  input [4:0] ADDRC,
-  input [4:0] ADDRD,
-  input [4:0] ADDRE,
-  input [4:0] ADDRF,
-  input [4:0] ADDRG,
-  input [4:0] ADDRH,
+  input [5:0] ADDRA,
+  input [5:0] ADDRB,
+  input [5:0] ADDRC,
+  input [5:0] ADDRD,
+  input [5:0] ADDRE,
+  input [5:0] ADDRF,
+  input [5:0] ADDRG,
+  input [5:0] ADDRH,
   input DIA,
   input DIB,
   input DIC,
diff --git a/techlibs/xilinx/cells_xtra.py b/techlibs/xilinx/cells_xtra.py
index e4c580b9d..6d5adf1aa 100644
--- a/techlibs/xilinx/cells_xtra.py
+++ b/techlibs/xilinx/cells_xtra.py
@@ -66,7 +66,7 @@ CELLS = [
     # CLB -- registers/latches.
     # Virtex 1/2/4/5, Spartan 3.
     Cell('FDCPE', port_attrs={'C': ['clkbuf_sink']}),
-    Cell('FDRSE', port_attrs={'C': ['clkbuf_sink']}),
+    # Cell('FDRSE', port_attrs={'C': ['clkbuf_sink']}),
     Cell('LDCPE', port_attrs={'C': ['clkbuf_sink']}),
     # Virtex 6, Spartan 6, Series 7, Ultrascale.
     # Cell('FDCE'),
diff --git a/techlibs/xilinx/cells_xtra.v b/techlibs/xilinx/cells_xtra.v
index 8ac596459..66b7c583f 100644
--- a/techlibs/xilinx/cells_xtra.v
+++ b/techlibs/xilinx/cells_xtra.v
@@ -17,27 +17,6 @@ module FDCPE (...);
     input PRE;
 endmodule
 
-module FDRSE (...);
-    parameter [0:0] INIT = 1'b0;
-    parameter [0:0] IS_C_INVERTED = 1'b0;
-    parameter [0:0] IS_CE_INVERTED = 1'b0;
-    parameter [0:0] IS_D_INVERTED = 1'b0;
-    parameter [0:0] IS_R_INVERTED = 1'b0;
-    parameter [0:0] IS_S_INVERTED = 1'b0;
-    output Q;
-    (* clkbuf_sink *)
-    (* invertible_pin = "IS_C_INVERTED" *)
-    input C;
-    (* invertible_pin = "IS_CE_INVERTED" *)
-    input CE;
-    (* invertible_pin = "IS_D_INVERTED" *)
-    input D;
-    (* invertible_pin = "IS_R_INVERTED" *)
-    input R;
-    (* invertible_pin = "IS_S_INVERTED" *)
-    input S;
-endmodule
-
 module LDCPE (...);
     parameter [0:0] INIT = 1'b0;
     parameter [0:0] IS_CLR_INVERTED = 1'b0;
diff --git a/techlibs/xilinx/lutrams.txt b/techlibs/xilinx/lutrams.txt
index 2613c206c..29f6b05cc 100644
--- a/techlibs/xilinx/lutrams.txt
+++ b/techlibs/xilinx/lutrams.txt
@@ -1,4 +1,17 @@
 
+bram $__XILINX_RAM16X1D
+  init 1
+  abits 4
+  dbits 1
+  groups 2
+  ports  1 1
+  wrmode 0 1
+  enable 0 1
+  transp 0 0
+  clocks 0 1
+  clkpol 0 2
+endbram
+
 bram $__XILINX_RAM32X1D
   init 1
   abits 5
@@ -38,6 +51,70 @@ bram $__XILINX_RAM128X1D
   clkpol 0 2
 endbram
 
+
+bram $__XILINX_RAM32X6SDP
+  init 1
+  abits 5
+  dbits 6
+  groups 2
+  ports  1 1
+  wrmode 0 1
+  enable 0 1
+  transp 0 0
+  clocks 0 1
+  clkpol 0 2
+endbram
+
+bram $__XILINX_RAM64X3SDP
+  init 1
+  abits 6
+  dbits 3
+  groups 2
+  ports  1 1
+  wrmode 0 1
+  enable 0 1
+  transp 0 0
+  clocks 0 1
+  clkpol 0 2
+endbram
+
+bram $__XILINX_RAM32X2Q
+  init 1
+  abits 5
+  dbits 2
+  groups 2
+  ports  3 1
+  wrmode 0 1
+  enable 0 1
+  transp 0 0
+  clocks 0 1
+  clkpol 0 2
+endbram
+
+bram $__XILINX_RAM64X1Q
+  init 1
+  abits 6
+  dbits 1
+  groups 2
+  ports  3 1
+  wrmode 0 1
+  enable 0 1
+  transp 0 0
+  clocks 0 1
+  clkpol 0 2
+endbram
+
+
+# Disabled for now, pending support for LUT4 arches
+#   since on LUT6 arches this occupies same area as
+#   a RAM32X1D
+#match $__XILINX_RAM16X1D
+#  min bits 2
+#  min wports 1
+#  make_outreg
+#  or_next_if_better
+#endmatch
+
 match $__XILINX_RAM32X1D
   min bits 3
   min wports 1
@@ -56,5 +133,35 @@ match $__XILINX_RAM128X1D
   min bits 9
   min wports 1
   make_outreg
+  or_next_if_better
+endmatch
+
+
+match $__XILINX_RAM32X6SDP
+  min bits 5
+  min wports 1
+  make_outreg
+  or_next_if_better
+endmatch
+
+match $__XILINX_RAM64X3SDP
+  min bits 6
+  min wports 1
+  make_outreg
+  or_next_if_better
+endmatch
+
+match $__XILINX_RAM32X2Q
+  min bits 5
+  min rports 3
+  min wports 1
+  make_outreg
+  or_next_if_better
 endmatch
 
+match $__XILINX_RAM64X1Q
+  min bits 5
+  min rports 3
+  min wports 1
+  make_outreg
+endmatch
diff --git a/techlibs/xilinx/lutrams_map.v b/techlibs/xilinx/lutrams_map.v
index 77041ca86..3ac1143bb 100644
--- a/techlibs/xilinx/lutrams_map.v
+++ b/techlibs/xilinx/lutrams_map.v
@@ -1,4 +1,36 @@
 
+module \$__XILINX_RAM16X1D (CLK1, A1ADDR, A1DATA, B1ADDR, B1DATA, B1EN);
+	parameter [15:0] INIT = 16'bx;
+	parameter CLKPOL2 = 1;
+	input CLK1;
+
+	input [3:0] A1ADDR;
+	output A1DATA;
+
+	input [3:0] B1ADDR;
+	input B1DATA;
+	input B1EN;
+
+	RAM16X1D #(
+		.INIT(INIT),
+		.IS_WCLK_INVERTED(!CLKPOL2)
+	) _TECHMAP_REPLACE_ (
+		.DPRA0(A1ADDR[0]),
+		.DPRA1(A1ADDR[1]),
+		.DPRA2(A1ADDR[2]),
+		.DPRA3(A1ADDR[3]),
+		.DPO(A1DATA),
+
+		.A0(B1ADDR[0]),
+		.A1(B1ADDR[1]),
+		.A2(B1ADDR[2]),
+		.A3(B1ADDR[3]),
+		.D(B1DATA),
+		.WCLK(CLK1),
+		.WE(B1EN)
+	);
+endmodule
+
 module \$__XILINX_RAM32X1D (CLK1, A1ADDR, A1DATA, B1ADDR, B1DATA, B1EN);
 	parameter [31:0] INIT = 32'bx;
 	parameter CLKPOL2 = 1;
@@ -95,3 +127,153 @@ module \$__XILINX_RAM128X1D (CLK1, A1ADDR, A1DATA, B1ADDR, B1DATA, B1EN);
 	);
 endmodule
 
+
+module \$__XILINX_RAM32X6SDP (CLK1, A1ADDR, A1DATA, B1ADDR, B1DATA, B1EN);
+	parameter [32*6-1:0] INIT = {32*6{1'bx}};
+	parameter CLKPOL2 = 1;
+	input CLK1;
+
+	input [4:0] A1ADDR;
+	output [5:0] A1DATA;
+
+	input [4:0] B1ADDR;
+	input [5:0] B1DATA;
+	input B1EN;
+
+	wire [1:0] DOD_unused;
+
+	RAM32M #(
+		.INIT_A({INIT[187:186], INIT[181:180], INIT[175:174], INIT[169:168], INIT[163:162], INIT[157:156], INIT[151:150], INIT[145:144], INIT[139:138], INIT[133:132], INIT[127:126], INIT[121:120], INIT[115:114], INIT[109:108], INIT[103:102], INIT[ 97: 96], INIT[ 91: 90], INIT[ 85: 84], INIT[ 79: 78], INIT[ 73: 72], INIT[ 67: 66], INIT[ 61: 60], INIT[ 55: 54], INIT[ 49: 48], INIT[ 43: 42], INIT[ 37: 36], INIT[ 31: 30], INIT[ 25: 24], INIT[ 19: 18], INIT[ 13: 12], INIT[  7:  6], INIT[  1:  0]}),
+		.INIT_B({INIT[189:188], INIT[183:182], INIT[177:176], INIT[171:170], INIT[165:164], INIT[159:158], INIT[153:152], INIT[147:146], INIT[141:140], INIT[135:134], INIT[129:128], INIT[123:122], INIT[117:116], INIT[111:110], INIT[105:104], INIT[ 99: 98], INIT[ 93: 92], INIT[ 87: 86], INIT[ 81: 80], INIT[ 75: 74], INIT[ 69: 68], INIT[ 63: 62], INIT[ 57: 56], INIT[ 51: 50], INIT[ 45: 44], INIT[ 39: 38], INIT[ 33: 32], INIT[ 27: 26], INIT[ 21: 20], INIT[ 15: 14], INIT[  9:  8], INIT[  3:  2]}),
+		.INIT_C({INIT[191:190], INIT[185:184], INIT[179:178], INIT[173:172], INIT[167:166], INIT[161:160], INIT[155:154], INIT[149:148], INIT[143:142], INIT[137:136], INIT[131:130], INIT[125:124], INIT[119:118], INIT[113:112], INIT[107:106], INIT[101:100], INIT[ 95: 94], INIT[ 89: 88], INIT[ 83: 82], INIT[ 77: 76], INIT[ 71: 70], INIT[ 65: 64], INIT[ 59: 58], INIT[ 53: 52], INIT[ 47: 46], INIT[ 41: 40], INIT[ 35: 34], INIT[ 29: 28], INIT[ 23: 22], INIT[ 17: 16], INIT[ 11: 10], INIT[  5:  4]}),
+		.INIT_D(64'bx),
+		.IS_WCLK_INVERTED(!CLKPOL2)
+	) _TECHMAP_REPLACE_ (
+		.ADDRA(A1ADDR),
+		.ADDRB(A1ADDR),
+		.ADDRC(A1ADDR),
+		.DOA(A1DATA[1:0]),
+		.DOB(A1DATA[3:2]),
+		.DOC(A1DATA[5:4]),
+		.DOD(DOD_unused),
+
+		.ADDRD(B1ADDR),
+		.DIA(B1DATA[1:0]),
+		.DIB(B1DATA[3:2]),
+		.DIC(B1DATA[5:4]),
+		.DID(2'b00),
+		.WCLK(CLK1),
+		.WE(B1EN)
+	);
+endmodule
+
+module \$__XILINX_RAM64X3SDP (CLK1, A1ADDR, A1DATA, B1ADDR, B1DATA, B1EN);
+	parameter [64*3-1:0] INIT = {64*3{1'bx}};
+	parameter CLKPOL2 = 1;
+	input CLK1;
+
+	input [5:0] A1ADDR;
+	output [2:0] A1DATA;
+
+	input [5:0] B1ADDR;
+	input [2:0] B1DATA;
+	input B1EN;
+
+	wire DOD_unused;
+
+	RAM64M #(
+		.INIT_A({INIT[189], INIT[186], INIT[183], INIT[180], INIT[177], INIT[174], INIT[171], INIT[168], INIT[165], INIT[162], INIT[159], INIT[156], INIT[153], INIT[150], INIT[147], INIT[144], INIT[141], INIT[138], INIT[135], INIT[132], INIT[129], INIT[126], INIT[123], INIT[120], INIT[117], INIT[114], INIT[111], INIT[108], INIT[105], INIT[102], INIT[ 99], INIT[ 96], INIT[ 93], INIT[ 90], INIT[ 87], INIT[ 84], INIT[ 81], INIT[ 78], INIT[ 75], INIT[ 72], INIT[ 69], INIT[ 66], INIT[ 63], INIT[ 60], INIT[ 57], INIT[ 54], INIT[ 51], INIT[ 48], INIT[ 45], INIT[ 42], INIT[ 39], INIT[ 36], INIT[ 33], INIT[ 30], INIT[ 27], INIT[ 24], INIT[ 21], INIT[ 18], INIT[ 15], INIT[ 12], INIT[  9], INIT[  6], INIT[  3], INIT[  0]}),
+		.INIT_B({INIT[190], INIT[187], INIT[184], INIT[181], INIT[178], INIT[175], INIT[172], INIT[169], INIT[166], INIT[163], INIT[160], INIT[157], INIT[154], INIT[151], INIT[148], INIT[145], INIT[142], INIT[139], INIT[136], INIT[133], INIT[130], INIT[127], INIT[124], INIT[121], INIT[118], INIT[115], INIT[112], INIT[109], INIT[106], INIT[103], INIT[100], INIT[ 97], INIT[ 94], INIT[ 91], INIT[ 88], INIT[ 85], INIT[ 82], INIT[ 79], INIT[ 76], INIT[ 73], INIT[ 70], INIT[ 67], INIT[ 64], INIT[ 61], INIT[ 58], INIT[ 55], INIT[ 52], INIT[ 49], INIT[ 46], INIT[ 43], INIT[ 40], INIT[ 37], INIT[ 34], INIT[ 31], INIT[ 28], INIT[ 25], INIT[ 22], INIT[ 19], INIT[ 16], INIT[ 13], INIT[ 10], INIT[  7], INIT[  4], INIT[  1]}),
+		.INIT_C({INIT[191], INIT[188], INIT[185], INIT[182], INIT[179], INIT[176], INIT[173], INIT[170], INIT[167], INIT[164], INIT[161], INIT[158], INIT[155], INIT[152], INIT[149], INIT[146], INIT[143], INIT[140], INIT[137], INIT[134], INIT[131], INIT[128], INIT[125], INIT[122], INIT[119], INIT[116], INIT[113], INIT[110], INIT[107], INIT[104], INIT[101], INIT[ 98], INIT[ 95], INIT[ 92], INIT[ 89], INIT[ 86], INIT[ 83], INIT[ 80], INIT[ 77], INIT[ 74], INIT[ 71], INIT[ 68], INIT[ 65], INIT[ 62], INIT[ 59], INIT[ 56], INIT[ 53], INIT[ 50], INIT[ 47], INIT[ 44], INIT[ 41], INIT[ 38], INIT[ 35], INIT[ 32], INIT[ 29], INIT[ 26], INIT[ 23], INIT[ 20], INIT[ 17], INIT[ 14], INIT[ 11], INIT[  8], INIT[  5], INIT[  2]}),
+		.INIT_D(64'bx),
+		.IS_WCLK_INVERTED(!CLKPOL2)
+	) _TECHMAP_REPLACE_ (
+		.ADDRA(A1ADDR),
+		.ADDRB(A1ADDR),
+		.ADDRC(A1ADDR),
+		.DOA(A1DATA[0]),
+		.DOB(A1DATA[1]),
+		.DOC(A1DATA[2]),
+		.DOD(DOD_unused),
+
+		.ADDRD(B1ADDR),
+		.DIA(B1DATA[0]),
+		.DIB(B1DATA[1]),
+		.DIC(B1DATA[2]),
+		.DID(1'b0),
+		.WCLK(CLK1),
+		.WE(B1EN)
+	);
+endmodule
+
+module \$__XILINX_RAM32X2Q (CLK1, A1ADDR, A1DATA, A2ADDR, A2DATA, A3ADDR, A3DATA, B1ADDR, B1DATA, B1EN);
+	parameter [63:0] INIT = 64'bx;
+	parameter CLKPOL2 = 1;
+	input CLK1;
+
+	input [4:0] A1ADDR, A2ADDR, A3ADDR;
+	output [1:0] A1DATA, A2DATA, A3DATA;
+
+	input [4:0] B1ADDR;
+	input [1:0] B1DATA;
+	input B1EN;
+
+	RAM32M #(
+		.INIT_A(INIT),
+		.INIT_B(INIT),
+		.INIT_C(INIT),
+		.INIT_D(INIT),
+		.IS_WCLK_INVERTED(!CLKPOL2)
+	) _TECHMAP_REPLACE_ (
+		.ADDRA(A1ADDR),
+		.ADDRB(A2ADDR),
+		.ADDRC(A3ADDR),
+		.DOA(A1DATA),
+		.DOB(A2DATA),
+		.DOC(A3DATA),
+
+		.ADDRD(B1ADDR),
+		.DIA(B1DATA),
+		.DIB(B1DATA),
+		.DIC(B1DATA),
+		.DID(B1DATA),
+		.WCLK(CLK1),
+		.WE(B1EN)
+	);
+endmodule
+
+module \$__XILINX_RAM64X1Q (CLK1, A1ADDR, A1DATA, A2ADDR, A2DATA, A3ADDR, A3DATA, B1ADDR, B1DATA, B1EN);
+	parameter [63:0] INIT = 64'bx;
+	parameter CLKPOL2 = 1;
+	input CLK1;
+
+	input [5:0] A1ADDR, A2ADDR, A3ADDR;
+	output A1DATA, A2DATA, A3DATA;
+
+	input [5:0] B1ADDR;
+	input B1DATA;
+	input B1EN;
+
+	RAM64M #(
+		.INIT_A(INIT),
+		.INIT_B(INIT),
+		.INIT_C(INIT),
+		.INIT_D(INIT),
+		.IS_WCLK_INVERTED(!CLKPOL2)
+	) _TECHMAP_REPLACE_ (
+		.ADDRA(A1ADDR),
+		.ADDRB(A2ADDR),
+		.ADDRC(A3ADDR),
+		.DOA(A1DATA),
+		.DOB(A2DATA),
+		.DOC(A3DATA),
+
+		.ADDRD(B1ADDR),
+		.DIA(B1DATA),
+		.DIB(B1DATA),
+		.DIC(B1DATA),
+		.DID(B1DATA),
+		.WCLK(CLK1),
+		.WE(B1EN)
+	);
+endmodule
diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc
index de262c8ad..ac6fedc58 100644
--- a/techlibs/xilinx/synth_xilinx.cc
+++ b/techlibs/xilinx/synth_xilinx.cc
@@ -445,6 +445,16 @@ struct SynthXilinxPass : public ScriptPass
 		}
 
 		if (check_label("map_ffram")) {
+			// Required for dffsr2dff to work.
+			run("simplemap t:$dff t:$adff t:$mux");
+			// Needs to be done before opt -mux_bool happens.
+			run("dffsr2dff");
+			if (help_mode)
+				run("dff2dffs [-match-init]", "(-match-init for xc6s only)");
+			else if (family == "xc6s")
+				run("dff2dffs -match-init");
+			else
+				run("dff2dffs");
 			if (widemux > 0)
 				run("opt -fast -mux_bool -undriven -fine"); // Necessary to omit -mux_undef otherwise muxcover
 									    // performs less efficiently
@@ -454,14 +464,11 @@ struct SynthXilinxPass : public ScriptPass
 		}
 
 		if (check_label("fine")) {
-			run("dffsr2dff");
-			run("dff2dffe");
+			run("dff2dffe -direct-match $_DFF_* -direct-match $__DFFS_*");
 			if (help_mode) {
-				run("simplemap t:$mux", "         ('-widemux' only)");
 				run("muxcover <internal options>, ('-widemux' only)");
 			}
 			else if (widemux > 0) {
-				run("simplemap t:$mux");
 				constexpr int cost_mux2 = 100;
 				std::string muxcover_args = stringf(" -nodecode -mux2=%d", cost_mux2);
 				switch (widemux) {
@@ -563,6 +570,7 @@ struct SynthXilinxPass : public ScriptPass
 			else if (!abc9)
 				techmap_args += stringf(" -map %s", ff_map_file.c_str());
 			run("techmap " + techmap_args, "(option without '-abc9')");
+			run("xilinx_dffopt");
 		}
 
 		if (check_label("finalize")) {
diff --git a/techlibs/xilinx/xc6s_ff_map.v b/techlibs/xilinx/xc6s_ff_map.v
index bf35b09e5..c40f446e0 100644
--- a/techlibs/xilinx/xc6s_ff_map.v
+++ b/techlibs/xilinx/xc6s_ff_map.v
@@ -27,6 +27,8 @@
 
 `ifndef _NO_FFS
 
+// No reset.
+
 module  \$_DFF_N_   (input D, C, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
@@ -46,6 +48,8 @@ module  \$_DFF_P_   (input D, C, output Q);
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
+// No reset, enable.
+
 module  \$_DFFE_NP_ (input D, C, E, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
@@ -65,80 +69,168 @@ module  \$_DFFE_PP_ (input D, C, E, output Q);
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
-module  \$_DFF_NN0_ (input D, C, R, output Q);
+// Async reset.
+
+module  \$_DFF_NP0_ (input D, C, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
     $error("Spartan 6 doesn't support FFs with asynchronous reset initialized to 1");
   else
-    FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR(!R));
+    FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_NP0_ (input D, C, R, output Q);
+module  \$_DFF_PP0_ (input D, C, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
     $error("Spartan 6 doesn't support FFs with asynchronous reset initialized to 1");
   else
-    FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
+    FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PN0_ (input D, C, R, output Q);
+
+module  \$_DFF_NP1_ (input D, C, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
+    $error("Spartan 6 doesn't support FFs with asynchronous set initialized to 0");
+  else
+    FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+module  \$_DFF_PP1_ (input D, C, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
+    $error("Spartan 6 doesn't support FFs with asynchronous set initialized to 0");
+  else
+    FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+// Async reset, enable.
+
+module  \$__DFFE_NP0 (input D, C, E, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
     $error("Spartan 6 doesn't support FFs with asynchronous reset initialized to 1");
   else
-    FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR(!R));
+    FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .CLR( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PP0_ (input D, C, R, output Q);
+module  \$__DFFE_PP0 (input D, C, E, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
     $error("Spartan 6 doesn't support FFs with asynchronous reset initialized to 1");
   else
-    FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
+    FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .CLR( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
-module  \$_DFF_NN1_ (input D, C, R, output Q);
+module  \$__DFFE_NP1 (input D, C, E, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
     $error("Spartan 6 doesn't support FFs with asynchronous set initialized to 0");
   else
-    FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE(!R));
+    FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .PRE( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_NP1_ (input D, C, R, output Q);
+module  \$__DFFE_PP1 (input D, C, E, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
     $error("Spartan 6 doesn't support FFs with asynchronous set initialized to 0");
   else
-    FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
+    FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .PRE( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+// Sync reset.
+
+module  \$__DFFS_NP0_ (input D, C, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
+    $error("Spartan 6 doesn't support FFs with reset initialized to 1");
+  else
+    FDRE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .R( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PN1_ (input D, C, R, output Q);
+module  \$__DFFS_PP0_ (input D, C, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
+    $error("Spartan 6 doesn't support FFs with reset initialized to 1");
+  else
+    FDRE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .R( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+module  \$__DFFS_NP1_ (input D, C, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
-    $error("Spartan 6 doesn't support FFs with asynchronous set initialized to 0");
+    $error("Spartan 6 doesn't support FFs with set initialized to 0");
   else
-    FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE(!R));
+    FDSE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .S( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PP1_ (input D, C, R, output Q);
+module  \$__DFFS_PP1_ (input D, C, R, output Q);
   parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
-    $error("Spartan 6 doesn't support FFs with asynchronous set initialized to 0");
+    $error("Spartan 6 doesn't support FFs with set initialized to 0");
   else
-    FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
+    FDSE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .S( R));
   endgenerate
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
+// Sync reset, enable.
+
+module  \$__DFFSE_NP0 (input D, C, E, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
+    $error("Spartan 6 doesn't support FFs with reset initialized to 1");
+  else
+    FDRE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .R( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+module  \$__DFFSE_PP0 (input D, C, E, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
+    $error("Spartan 6 doesn't support FFs with reset initialized to 1");
+  else
+    FDRE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .R( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+module  \$__DFFSE_NP1 (input D, C, E, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
+    $error("Spartan 6 doesn't support FFs with set initialized to 0");
+  else
+    FDSE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .S( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+module  \$__DFFSE_PP1 (input D, C, E, R, output Q);
+  parameter [0:0] _TECHMAP_WIREINIT_Q_ = 1'bx;
+  generate if (_TECHMAP_WIREINIT_Q_ === 1'b0)
+    $error("Spartan 6 doesn't support FFs with set initialized to 0");
+  else
+    FDSE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .S( R));
+  endgenerate
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+// Latches (no reset).
+
 module  \$_DLATCH_N_ (input E, D, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
   generate if (_TECHMAP_WIREINIT_Q_ === 1'b1)
@@ -158,5 +250,7 @@ module  \$_DLATCH_P_ (input E, D, output Q);
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
+// Latches with reset (TODO).
+
 `endif
 
diff --git a/techlibs/xilinx/xc7_ff_map.v b/techlibs/xilinx/xc7_ff_map.v
index 32ca9f560..2bd874457 100644
--- a/techlibs/xilinx/xc7_ff_map.v
+++ b/techlibs/xilinx/xc7_ff_map.v
@@ -37,6 +37,8 @@
 
 `ifndef _NO_FFS
 
+// No reset.
+
 module  \$_DFF_N_   (input D, C, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
   FDRE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .R(1'b0));
@@ -48,6 +50,8 @@ module  \$_DFF_P_   (input D, C, output Q);
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
+// No reset, enable.
+
 module  \$_DFFE_NP_ (input D, C, E, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
   FDRE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E),    .R(1'b0));
@@ -59,47 +63,103 @@ module  \$_DFFE_PP_ (input D, C, E, output Q);
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
-module  \$_DFF_NN0_ (input D, C, R, output Q);
+// Async reset.
+
+module  \$_DFF_NP0_ (input D, C, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR(!R));
+  FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_NP0_ (input D, C, R, output Q);
+module  \$_DFF_PP0_ (input D, C, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
+  FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PN0_ (input D, C, R, output Q);
+
+module  \$_DFF_NP1_ (input D, C, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR(!R));
+  FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PP0_ (input D, C, R, output Q);
+module  \$_DFF_PP1_ (input D, C, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .CLR( R));
+  FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
-module  \$_DFF_NN1_ (input D, C, R, output Q);
+// Async reset, enable.
+
+module  \$__DFFE_NP0 (input D, C, E, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE(!R));
+  FDCE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .CLR( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_NP1_ (input D, C, R, output Q);
+module  \$__DFFE_PP0 (input D, C, E, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
+  FDCE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .CLR( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PN1_ (input D, C, R, output Q);
+
+module  \$__DFFE_NP1 (input D, C, E, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE(!R));
+  FDPE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .PRE( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
-module  \$_DFF_PP1_ (input D, C, R, output Q);
+module  \$__DFFE_PP1 (input D, C, E, R, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
-  FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .PRE( R));
+  FDPE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .PRE( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+// Sync reset.
+
+module  \$__DFFS_NP0_ (input D, C, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDRE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .R( R));
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
+module  \$__DFFS_PP0_ (input D, C, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDRE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .R( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+module  \$__DFFS_NP1_ (input D, C, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDSE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .S( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+module  \$__DFFS_PP1_ (input D, C, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDSE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(1'b1), .S( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+// Sync reset, enable.
+
+module  \$__DFFSE_NP0 (input D, C, E, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDRE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .R( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+module  \$__DFFSE_PP0 (input D, C, E, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDRE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .R( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+module  \$__DFFSE_NP1 (input D, C, E, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDSE_1 #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .S( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+module  \$__DFFSE_PP1 (input D, C, E, R, output Q);
+  parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
+  FDSE   #(.INIT(_TECHMAP_WIREINIT_Q_)) _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(E), .S( R));
+  wire _TECHMAP_REMOVEINIT_Q_ = 1;
+endmodule
+
+// Latches (no reset).
 
 module  \$_DLATCH_N_ (input E, D, output Q);
   parameter _TECHMAP_WIREINIT_Q_ = 1'bx;
@@ -112,5 +172,7 @@ module  \$_DLATCH_P_ (input E, D, output Q);
   wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
+// Latches with reset (TODO).
+
 `endif
 
diff --git a/techlibs/xilinx/xc7_xcu_brams.txt b/techlibs/xilinx/xc7_xcu_brams.txt
index f1161114e..c63218ae1 100644
--- a/techlibs/xilinx/xc7_xcu_brams.txt
+++ b/techlibs/xilinx/xc7_xcu_brams.txt
@@ -1,4 +1,3 @@
-
 bram $__XILINX_RAMB36_SDP
   init 1
   abits 9
@@ -72,34 +71,79 @@ bram $__XILINX_RAMB18_TDP
   clkpol 2 3
 endbram
 
+# The "min bits" value were taken from:
+# [[CITE]] 7 Series FPGAs Memory Resources User Guide (UG473),
+# v1.14 ed., p 29-30, July, 2019.
+# https://www.xilinx.com/support/documentation/user_guides/ug473_7Series_Memory_Resources.pdf
+
 match $__XILINX_RAMB36_SDP
-  min bits 4096
+  attribute !ram_style
+  attribute !logic_block
+  min bits 1024
   min efficiency 5
   shuffle_enable B
   make_transp
   or_next_if_better
 endmatch
 
+match $__XILINX_RAMB36_SDP
+  attribute ram_style=block ram_block
+  attribute !logic_block
+  shuffle_enable B
+  make_transp
+  or_next_if_better
+endmatch
+
 match $__XILINX_RAMB18_SDP
-  min bits 4096
+  attribute !ram_style
+  attribute !logic_block
+  min bits 1024
   min efficiency 5
   shuffle_enable B
   make_transp
   or_next_if_better
 endmatch
 
+match $__XILINX_RAMB18_SDP
+  attribute ram_style=block ram_block
+  attribute !logic_block
+  shuffle_enable B
+  make_transp
+  or_next_if_better
+endmatch
+
 match $__XILINX_RAMB36_TDP
-  min bits 4096
+  attribute !ram_style
+  attribute !logic_block
+  min bits 1024
   min efficiency 5
   shuffle_enable B
   make_transp
   or_next_if_better
 endmatch
 
+match $__XILINX_RAMB36_TDP
+  attribute ram_style=block ram_block
+  attribute !logic_block
+  shuffle_enable B
+  make_transp
+  or_next_if_better
+endmatch
+
 match $__XILINX_RAMB18_TDP
-  min bits 4096
+  attribute !ram_style
+  attribute !logic_block
+  min bits 1024
   min efficiency 5
   shuffle_enable B
   make_transp
+  or_next_if_better
+endmatch
+
+match $__XILINX_RAMB18_TDP
+  attribute ram_style=block ram_block
+  attribute !logic_block
+  shuffle_enable B
+  make_transp
 endmatch
 
diff --git a/techlibs/xilinx/xilinx_dffopt.cc b/techlibs/xilinx/xilinx_dffopt.cc
new file mode 100644
index 000000000..1256a08cb
--- /dev/null
+++ b/techlibs/xilinx/xilinx_dffopt.cc
@@ -0,0 +1,351 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "kernel/yosys.h"
+#include "kernel/sigtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+typedef std::pair<Const, std::vector<SigBit>> LutData;
+
+// Compute a LUT implementing (select ^ select_inv) ? alt_data : data.  Returns true if successful.
+bool merge_lut(LutData &result, const LutData &data, const LutData select, bool select_inv, SigBit alt_data, int max_lut_size) {
+	// First, gather input signals.
+	result.second = data.second;
+	int idx_alt = -1;
+	if (alt_data.wire) {
+		// Check if we already have it.
+		for (int i = 0; i < GetSize(result.second); i++)
+			if (result.second[i] == alt_data)
+				idx_alt = i;
+		// If not, add it.
+		if (idx_alt == -1) {
+			idx_alt = GetSize(result.second);
+			result.second.push_back(alt_data);
+		}
+	}
+	std::vector<int> idx_sel;
+	for (auto bit : select.second) {
+		int idx = -1;
+		for (int i = 0; i < GetSize(result.second); i++)
+			if (result.second[i] == bit)
+				idx = i;
+		if (idx == -1) {
+			idx = GetSize(result.second);
+			result.second.push_back(bit);
+		}
+		idx_sel.push_back(idx);
+	}
+
+	// If LUT would be too large, bail.
+	if (GetSize(result.second) > max_lut_size)
+		return false;
+
+	// Okay, we're doing it — compute the LUT mask.
+	result.first = Const(0, 1 << GetSize(result.second));
+	for (int i = 0; i < GetSize(result.first); i++) {
+		int sel_lut_idx = 0;
+		for (int j = 0; j < GetSize(select.second); j++)
+			if (i & 1 << idx_sel[j])
+				sel_lut_idx |= 1 << j;
+		bool select_val = (select.first.bits[sel_lut_idx] == State::S1);
+		bool new_bit;
+		if (select_val ^ select_inv) {
+			// Use alt_data.
+			if (alt_data.wire)
+				new_bit = (i & 1 << idx_alt) != 0;
+			else
+				new_bit = alt_data.data == State::S1;
+		} else {
+			// Use original LUT.
+			int lut_idx = i & ((1 << GetSize(data.second)) - 1);
+			new_bit = data.first.bits[lut_idx] == State::S1;
+		}
+		result.first.bits[i] = new_bit ? State::S1 : State::S0;
+	}
+	return true;
+}
+
+struct XilinxDffOptPass : public Pass {
+	XilinxDffOptPass() : Pass("xilinx_dffopt", "Xilinx: optimize FF control signal usage") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    xilinx_dffopt [options] [selection]\n");
+		log("\n");
+		log("Converts hardware clock enable and set/reset signals on FFs to emulation\n");
+		log("using LUTs, if doing so would improve area.  Operates on post-techmap Xilinx\n");
+		log("cells (LUT*, FD*).\n");
+		log("\n");
+		log("    -lut4\n");
+		log("        Assume a LUT4-based device (instead of a LUT6-based device).\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		log_header(design, "Executing XILINX_DFFOPT pass (optimize FF control signal usage).\n");
+
+		size_t argidx;
+		int max_lut_size = 6;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			if (args[argidx] == "-lut4") {
+				max_lut_size = 4;
+				continue;
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		for (auto module : design->selected_modules())
+		{
+			log("Optimizing FFs in %s.\n", log_id(module));
+
+			SigMap sigmap(module);
+			dict<SigBit, pair<LutData, Cell *>> bit_to_lut;
+			dict<SigBit, int> bit_uses;
+
+			// Gather LUTs.
+			for (auto cell : module->selected_cells())
+			{
+				for (auto port : cell->connections())
+					for (auto bit : port.second)
+						bit_uses[sigmap(bit)]++;
+				if (cell->get_bool_attribute(ID::keep))
+					continue;
+				if (cell->type == ID(INV)) {
+					SigBit sigout = sigmap(cell->getPort(ID(O)));
+					SigBit sigin = sigmap(cell->getPort(ID(I)));
+					bit_to_lut[sigout] = make_pair(LutData(Const(1, 2), {sigin}), cell);
+				} else if (cell->type.in(ID(LUT1), ID(LUT2), ID(LUT3), ID(LUT4), ID(LUT5), ID(LUT6))) {
+					SigBit sigout = sigmap(cell->getPort(ID(O)));
+					const Const &init = cell->getParam(ID(INIT));
+					std::vector<SigBit> sigin;
+					sigin.push_back(sigmap(cell->getPort(ID(I0))));
+					if (cell->type == ID(LUT1))
+						goto lut_sigin_done;
+					sigin.push_back(sigmap(cell->getPort(ID(I1))));
+					if (cell->type == ID(LUT2))
+						goto lut_sigin_done;
+					sigin.push_back(sigmap(cell->getPort(ID(I2))));
+					if (cell->type == ID(LUT3))
+						goto lut_sigin_done;
+					sigin.push_back(sigmap(cell->getPort(ID(I3))));
+					if (cell->type == ID(LUT4))
+						goto lut_sigin_done;
+					sigin.push_back(sigmap(cell->getPort(ID(I4))));
+					if (cell->type == ID(LUT5))
+						goto lut_sigin_done;
+					sigin.push_back(sigmap(cell->getPort(ID(I5))));
+lut_sigin_done:
+					bit_to_lut[sigout] = make_pair(LutData(init, sigin), cell);
+				}
+			}
+			for (auto wire : module->wires())
+				if (wire->port_output || wire->port_input)
+					for (int i = 0; i < GetSize(wire); i++)
+						bit_uses[sigmap(SigBit(wire, i))]++;
+
+			// Iterate through FFs.
+			for (auto cell : module->selected_cells())
+			{
+				bool has_s = false, has_r = false;
+				if (cell->type.in(ID(FDCE), ID(FDPE), ID(FDCPE), ID(FDCE_1), ID(FDPE_1), ID(FDCPE_1))) {
+					// Async reset.
+				} else if (cell->type.in(ID(FDRE), ID(FDRE_1))) {
+					has_r = true;
+				} else if (cell->type.in(ID(FDSE), ID(FDSE_1))) {
+					has_s = true;
+				} else if (cell->type.in(ID(FDRSE), ID(FDRSE_1))) {
+					has_r = true;
+					has_s = true;
+				} else {
+					// Not a FF.
+					continue;
+				}
+				if (cell->get_bool_attribute(ID::keep))
+					continue;
+
+				// Don't bother if D has more than one use.
+				SigBit sig_D = sigmap(cell->getPort(ID(D)));
+				if (bit_uses[sig_D] > 2)
+					continue;
+
+				// Find the D LUT.
+				auto it_D = bit_to_lut.find(sig_D);
+				if (it_D == bit_to_lut.end())
+					continue;
+				LutData lut_d = it_D->second.first;
+				Cell *cell_d = it_D->second.second;
+				if (cell->hasParam(ID(IS_D_INVERTED)) && cell->getParam(ID(IS_D_INVERTED)).as_bool()) {
+					// Flip all bits in the LUT.
+					for (int i = 0; i < GetSize(lut_d.first); i++)
+						lut_d.first.bits[i] = (lut_d.first.bits[i] == State::S1) ? State::S0 : State::S1;
+				}
+
+				LutData lut_d_post_ce;
+				LutData lut_d_post_s;
+				LutData lut_d_post_r;
+				bool worthy_post_ce = false;
+				bool worthy_post_s = false;
+				bool worthy_post_r = false;
+
+				// First, unmap CE.
+				SigBit sig_Q = sigmap(cell->getPort(ID(Q)));
+				SigBit sig_CE = sigmap(cell->getPort(ID(CE)));
+				LutData lut_ce = LutData(Const(2, 2), {sig_CE});
+				auto it_CE = bit_to_lut.find(sig_CE);
+				if (it_CE != bit_to_lut.end())
+					lut_ce = it_CE->second.first;
+				if (sig_CE.wire) {
+					// Merge CE LUT and D LUT into one.  If it cannot be done, nothing to do about this FF.
+					if (!merge_lut(lut_d_post_ce, lut_d, lut_ce, true, sig_Q, max_lut_size))
+						continue;
+
+					// If this gets rid of a CE LUT, it's worth it.  If not, it still may be worth it, if we can remove set/reset as well.
+					if (it_CE != bit_to_lut.end())
+						worthy_post_ce = true;
+				} else if (sig_CE.data != State::S1) {
+					// Strange.  Should not happen in a reasonable flow, so bail.
+					continue;
+				} else {
+					lut_d_post_ce = lut_d;
+				}
+
+				// Second, unmap S, if any.
+				lut_d_post_s = lut_d_post_ce;
+				if (has_s) {
+					SigBit sig_S = sigmap(cell->getPort(ID(S)));
+					LutData lut_s = LutData(Const(2, 2), {sig_S});
+					bool inv_s = cell->hasParam(ID(IS_S_INVERTED)) && cell->getParam(ID(IS_S_INVERTED)).as_bool();
+					auto it_S = bit_to_lut.find(sig_S);
+					if (it_S != bit_to_lut.end())
+						lut_s = it_S->second.first;
+					if (sig_S.wire) {
+						// Merge S LUT and D LUT into one.  If it cannot be done, try to at least merge CE.
+						if (!merge_lut(lut_d_post_s, lut_d_post_ce, lut_s, inv_s, SigBit(State::S1), max_lut_size))
+							goto unmap;
+						// If this gets rid of an S LUT, it's worth it.
+						if (it_S != bit_to_lut.end())
+							worthy_post_s = true;
+					} else if (sig_S.data != (inv_s ? State::S1 : State::S0)) {
+						// Strange.  Should not happen in a reasonable flow, so bail.
+						continue;
+					}
+				}
+
+				// Third, unmap R, if any.
+				lut_d_post_r = lut_d_post_s;
+				if (has_r) {
+					SigBit sig_R = sigmap(cell->getPort(ID(R)));
+					LutData lut_r = LutData(Const(2, 2), {sig_R});
+					bool inv_r = cell->hasParam(ID(IS_R_INVERTED)) && cell->getParam(ID(IS_R_INVERTED)).as_bool();
+					auto it_R = bit_to_lut.find(sig_R);
+					if (it_R != bit_to_lut.end())
+						lut_r = it_R->second.first;
+					if (sig_R.wire) {
+						// Merge R LUT and D LUT into one.  If it cannot be done, try to at least merge CE/S.
+						if (!merge_lut(lut_d_post_r, lut_d_post_s, lut_r, inv_r, SigBit(State::S0), max_lut_size))
+							goto unmap;
+						// If this gets rid of an S LUT, it's worth it.
+						if (it_R != bit_to_lut.end())
+							worthy_post_r = true;
+					} else if (sig_R.data != (inv_r ? State::S1 : State::S0)) {
+						// Strange.  Should not happen in a reasonable flow, so bail.
+						continue;
+					}
+				}
+
+unmap:
+				LutData final_lut;
+				if (worthy_post_r) {
+					final_lut = lut_d_post_r;
+					log("  Merging R LUT for %s/%s (%d -> %d)\n", log_id(cell), log_id(sig_Q.wire), GetSize(lut_d.second), GetSize(final_lut.second));
+				} else if (worthy_post_s) {
+					final_lut = lut_d_post_s;
+					log("  Merging S LUT for %s/%s (%d -> %d)\n", log_id(cell), log_id(sig_Q.wire), GetSize(lut_d.second), GetSize(final_lut.second));
+				} else if (worthy_post_ce) {
+					final_lut = lut_d_post_ce;
+					log("  Merging CE LUT for %s/%s (%d -> %d)\n", log_id(cell), log_id(sig_Q.wire), GetSize(lut_d.second), GetSize(final_lut.second));
+				} else {
+					// Nothing to do here.
+					continue;
+				}
+
+				// Okay, we're doing it.  Unmap ports.
+				if (worthy_post_r) {
+					cell->unsetParam(ID(IS_R_INVERTED));
+					cell->setPort(ID(R), Const(0, 1));
+				}
+				if (has_s && (worthy_post_r || worthy_post_s)) {
+					cell->unsetParam(ID(IS_S_INVERTED));
+					cell->setPort(ID(S), Const(0, 1));
+				}
+				cell->setPort(ID(CE), Const(1, 1));
+				cell->unsetParam(ID(IS_D_INVERTED));
+
+				// Create the new LUT.
+				Cell *lut_cell = 0;
+				switch (GetSize(final_lut.second)) {
+					case 1:
+						lut_cell = module->addCell(NEW_ID, ID(LUT1));
+						break;
+					case 2:
+						lut_cell = module->addCell(NEW_ID, ID(LUT2));
+						break;
+					case 3:
+						lut_cell = module->addCell(NEW_ID, ID(LUT3));
+						break;
+					case 4:
+						lut_cell = module->addCell(NEW_ID, ID(LUT4));
+						break;
+					case 5:
+						lut_cell = module->addCell(NEW_ID, ID(LUT5));
+						break;
+					case 6:
+						lut_cell = module->addCell(NEW_ID, ID(LUT6));
+						break;
+					default:
+						log_assert(!"unknown lut size");
+				}
+				lut_cell->attributes = cell_d->attributes;
+				Wire *lut_out = module->addWire(NEW_ID);
+				lut_cell->setParam(ID(INIT), final_lut.first);
+				cell->setPort(ID(D), lut_out);
+				lut_cell->setPort(ID(O), lut_out);
+				lut_cell->setPort(ID(I0), final_lut.second[0]);
+				if (GetSize(final_lut.second) >= 2)
+					lut_cell->setPort(ID(I1), final_lut.second[1]);
+				if (GetSize(final_lut.second) >= 3)
+					lut_cell->setPort(ID(I2), final_lut.second[2]);
+				if (GetSize(final_lut.second) >= 4)
+					lut_cell->setPort(ID(I3), final_lut.second[3]);
+				if (GetSize(final_lut.second) >= 5)
+					lut_cell->setPort(ID(I4), final_lut.second[4]);
+				if (GetSize(final_lut.second) >= 6)
+					lut_cell->setPort(ID(I5), final_lut.second[5]);
+			}
+		}
+	}
+} XilinxDffOptPass;
+
+PRIVATE_NAMESPACE_END
+