opt_clean: Remove init attribute bits together with removed DFFs.

Fixes #2546.

2 files changed, 24 insertions, 11 deletions

diff --git a/passes/opt/opt_clean.cc b/passes/opt/opt_clean.cc
index 883374cf6..c66f45308 100644
--- a/passes/opt/opt_clean.cc
+++ b/passes/opt/opt_clean.cc
@@ -21,6 +21,7 @@
 #include "kernel/sigtools.h"
 #include "kernel/log.h"
 #include "kernel/celltypes.h"
+#include "kernel/ffinit.h"
 #include <stdlib.h>
 #include <stdio.h>
 #include <set>
@@ -101,6 +102,7 @@ void rmunused_module_cells(Module *module, bool verbose)
 	pool<SigBit> used_raw_bits;
 	dict<SigBit, pool<Cell*>> wire2driver;
 	dict<SigBit, vector<string>> driver_driver_logs;
+	FfInitVals ffinit(&sigmap, module);
 
 	SigMap raw_sigmap;
 	for (auto &it : module->connections_) {
@@ -193,6 +195,8 @@ void rmunused_module_cells(Module *module, bool verbose)
 		if (verbose)
 			log_debug("  removing unused `%s' cell `%s'.\n", cell->type.c_str(), cell->name.c_str());
 		module->design->scratchpad_set_bool("opt.did_something", true);
+		if (RTLIL::builtin_ff_cell_types().count(cell->type))
+			ffinit.remove_init(cell->getPort(ID::Q));
 		module->remove(cell);
 		count_rm_cells++;
 	}
diff --git a/tests/opt/opt_clean_init.ys b/tests/opt/opt_clean_init.ys
index 0d567608d..7933f3e17 100644
--- a/tests/opt/opt_clean_init.ys
+++ b/tests/opt/opt_clean_init.ys
@@ -1,13 +1,22 @@
-logger -expect warning "Initial value conflict for \\y resolving to 1'0 but with init 1'1" 1
-logger -expect-no-warnings
-read_verilog <<EOT
-module top;
-(* init=1'b0 *) wire w = 1'b0;
-(* init=1'bx *) wire x = 1'b0;
-(* init=1'b1 *) wire y = 1'b0;
-(* init=1'b0 *) wire z = 1'bx;
+read_verilog << EOT
+module top(...);
+
+input [1:0] D;
+input C;
+output O;
+reg [1:0] Q;
+
+initial Q = 0;
+
+always @(posedge C)
+        Q <= D;
+
+assign O = Q[1];
+
 endmodule
 EOT
-clean
-select -assert-count 1 a:init
-select -assert-count 1 w:y a:init %i
+
+synth
+check -assert -initdrv
+
+select -assert-count 1 a:init=2'b0x