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diff --git a/tests/simple/i2c_master_tests.v b/tests/simple/i2c_master_tests.v
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+++ b/tests/simple/i2c_master_tests.v
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+// one of my early test cases was the OpenCores I2C master
+// This is a collection of stripped down code snippets from
+// this core that triggered bugs in early versions of yosys.
+
+// from i2c_master_bit_ctrl
+module test01(clk, rst, nReset, al);
+
+	input clk, rst, nReset;
+	output reg al;
+
+	reg cmd_stop;
+	always @(posedge clk or negedge nReset)
+	  if (~nReset)
+	    cmd_stop <= #1 1'b0;
+	  else if (rst)
+	    cmd_stop <= #1 1'b0;
+
+	always @(posedge clk or negedge nReset)
+	  if (~nReset)
+	    al <= #1 1'b0;
+	  else if (rst)
+	    al <= #1 1'b0;
+	  else
+	    al <= #1 ~cmd_stop;
+
+endmodule
+
+// from i2c_master_bit_ctrl
+module test02(clk, slave_wait, clk_cnt, cmd, cmd_stop, cnt);
+
+	input clk, slave_wait, clk_cnt;
+	input cmd;
+
+	output reg cmd_stop;
+
+	reg clk_en;
+	output reg [15:0] cnt;
+
+	always @(posedge clk)
+	  if (~|cnt)
+	    if (~slave_wait)
+	      begin
+	          cnt    <= #1 clk_cnt;
+	          clk_en <= #1 1'b1;
+	      end
+	    else
+	      begin
+	          cnt    <= #1 cnt;
+	          clk_en <= #1 1'b0;
+	      end
+	  else
+	    begin
+                cnt    <= #1 cnt - 16'h1;
+	        clk_en <= #1 1'b0;
+	    end
+
+	always @(posedge clk)
+	  if (clk_en)
+	    cmd_stop <= #1 cmd;
+
+endmodule
+