xilinx: Use INV instead of LUT1 when applicable

techlibs/xilinx/lut_map.v

diff --git a/techlibs/xilinx/lut_map.v b/techlibs/xilinx/lut_map.v
index 13d3c32..62d5016 100644
--- a/techlibs/xilinx/lut_map.v
+++ b/techlibs/xilinx/lut_map.v
@@ -56,8 +56,12 @@
 
   generate
     if (WIDTH == 1) begin
-      LUT1 #(.INIT(P_LUT)) _TECHMAP_REPLACE_ (.O(Y),
-        .I0(A[0]));
+      if (P_LUT == 2'b01) begin
+        INV _TECHMAP_REPLACE_ (.O(Y), .I(A[0]));
+      end else begin
+        LUT1 #(.INIT(P_LUT)) _TECHMAP_REPLACE_ (.O(Y),
+          .I0(A[0]));
+      end
     end else
     if (WIDTH == 2) begin
       LUT2 #(.INIT(P_LUT)) _TECHMAP_REPLACE_ (.O(Y),

tests/arch/xilinx/adffs.ys

diff --git a/tests/arch/xilinx/adffs.ys b/tests/arch/xilinx/adffs.ys
index 12c3441..e73bfe0 100644
--- a/tests/arch/xilinx/adffs.ys
+++ b/tests/arch/xilinx/adffs.ys
@@ -20,9 +20,9 @@
 cd adffn # Constrain all select calls below inside the top module
 select -assert-count 1 t:BUFG
 select -assert-count 1 t:FDCE
-select -assert-count 1 t:LUT1
+select -assert-count 1 t:INV
 
-select -assert-none t:BUFG t:FDCE t:LUT1 %% t:* %D
+select -assert-none t:BUFG t:FDCE t:INV %% t:* %D
 
 
 design -load read

tests/arch/xilinx/counter.ys

diff --git a/tests/arch/xilinx/counter.ys b/tests/arch/xilinx/counter.ys
index 57b645d..604acdb 100644
--- a/tests/arch/xilinx/counter.ys
+++ b/tests/arch/xilinx/counter.ys
@@ -8,7 +8,7 @@
 
 select -assert-count 1 t:BUFG
 select -assert-count 8 t:FDCE
-select -assert-count 1 t:LUT1
+select -assert-count 1 t:INV
 select -assert-count 7 t:MUXCY
 select -assert-count 8 t:XORCY
-select -assert-none t:BUFG t:FDCE t:LUT1 t:MUXCY t:XORCY %% t:* %D
+select -assert-none t:BUFG t:FDCE t:INV t:MUXCY t:XORCY %% t:* %D

tests/arch/xilinx/latches.ys

diff --git a/tests/arch/xilinx/latches.ys b/tests/arch/xilinx/latches.ys
index fe7887e..c87a8e3 100644
--- a/tests/arch/xilinx/latches.ys
+++ b/tests/arch/xilinx/latches.ys
@@ -18,9 +18,9 @@
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd latchn # Constrain all select calls below inside the top module
 select -assert-count 1 t:LDCE
-select -assert-count 1 t:LUT1
+select -assert-count 1 t:INV
 
-select -assert-none t:LDCE t:LUT1 %% t:* %D
+select -assert-none t:LDCE t:INV %% t:* %D
 
 
 design -load read

tests/arch/xilinx/logic.ys

diff --git a/tests/arch/xilinx/logic.ys b/tests/arch/xilinx/logic.ys
index c0f6da3..d5b5c1a 100644
--- a/tests/arch/xilinx/logic.ys
+++ b/tests/arch/xilinx/logic.ys
@@ -5,7 +5,7 @@
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd top # Constrain all select calls below inside the top module
 
-select -assert-count 1 t:LUT1
+select -assert-count 1 t:INV
 select -assert-count 6 t:LUT2
 select -assert-count 2 t:LUT4
-select -assert-none t:LUT1 t:LUT2 t:LUT4 %% t:* %D
+select -assert-none t:INV t:LUT2 t:LUT4 %% t:* %D