From cd8f55a91100b8dcf8b4775803cbacf70f5a998c Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddie@fpgeh.com>
Date: Tue, 21 Jan 2020 09:43:04 -0800
Subject: write_xaiger: fix for (* keep *) on flop output

---
 backends/aiger/xaiger.cc |  6 +++---
 tests/various/abc9.ys    | 15 +++++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index a9b75ecc7..b72dd6890 100644
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -222,6 +222,8 @@ struct XAigerWriter
 					alias_map[Q] = D;
 					auto r YS_ATTRIBUTE(unused) = ff_bits.insert(std::make_pair(D, cell));
 					log_assert(r.second);
+					if (input_bits.erase(Q))
+						log_assert(Q.wire->attributes.count(ID::keep));
 					continue;
 				}
 
@@ -568,9 +570,6 @@ struct XAigerWriter
 		//	write_o_buffer(0);
 
 		if (!box_list.empty() || !ff_bits.empty()) {
-			RTLIL::Module *holes_module = module->design->module(stringf("%s$holes", module->name.c_str()));
-			log_assert(holes_module);
-
 			dict<IdString, std::tuple<int,int,int>> cell_cache;
 
 			int box_count = 0;
@@ -653,6 +652,7 @@ struct XAigerWriter
 			f.write(reinterpret_cast<const char*>(&buffer_size_be), sizeof(buffer_size_be));
 			f.write(buffer_str.data(), buffer_str.size());
 
+			RTLIL::Module *holes_module = module->design->module(stringf("%s$holes", module->name.c_str()));
 			if (holes_module) {
 				std::stringstream a_buffer;
 				XAigerWriter writer(holes_module, true /* holes_mode */);
diff --git a/tests/various/abc9.ys b/tests/various/abc9.ys
index 81d0afd1b..0c7695089 100644
--- a/tests/various/abc9.ys
+++ b/tests/various/abc9.ys
@@ -14,6 +14,7 @@ design -import gate -as gate
 miter -equiv -flatten -make_assert -make_outputs gold gate miter
 sat -verify -prove-asserts -show-ports miter
 
+
 design -load read
 hierarchy -top abc9_test028
 proc
@@ -23,6 +24,7 @@ select -assert-count 1 t:$lut r:LUT=2'b01 r:WIDTH=1 %i %i
 select -assert-count 1 t:unknown
 select -assert-none t:$lut t:unknown %% t: %D
 
+
 design -load read
 hierarchy -top abc9_test032
 proc
@@ -38,3 +40,16 @@ design -import gate -as gate
 
 miter -equiv -flatten -make_assert -make_outputs gold gate miter
 sat -seq 10 -verify -prove-asserts -show-ports miter
+
+
+design -reset
+read_verilog -icells <<EOT
+module abc9_test036(input clk, d, output q);
+(* keep *) reg w;
+$__ABC9_FF_ ff(.D(d), .Q(w));
+wire \ff.clock = clk;
+wire \ff.init = 1'b0;
+assign q = w;
+endmodule
+EOT
+abc9 -lut 4 -dff
-- 
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