From 227a2d91df59aed4aa4f54a575dd480b742bfe0a Mon Sep 17 00:00:00 2001
From: Rodrigo Arias <rodrigo.arias@bsc.es>
Date: Wed, 11 Jan 2023 12:08:28 +0100
Subject: [PATCH] Allow duplicates in the mux output channel

---
 src/emu/mux.c   |  4 ++++
 test/unit/mux.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/emu/mux.c b/src/emu/mux.c
index 1e7d37e..43f1492 100644
--- a/src/emu/mux.c
+++ b/src/emu/mux.c
@@ -144,6 +144,10 @@ mux_init(struct mux *mux,
 	 * input and select channel at the same time. */
 	chan_prop_set(output, CHAN_DIRTY_WRITE, 1);
 
+	/* Similarly, we may switch to an input channel that has the same value
+	 * as the last output value, so we allow duplicates too */
+	chan_prop_set(output, CHAN_DUPLICATES, 1);
+
 	memset(mux, 0, sizeof(struct mux_input));
 	mux->select = select;
 	mux->output = output;
diff --git a/test/unit/mux.c b/test/unit/mux.c
index 862b995..112fffd 100644
--- a/test/unit/mux.c
+++ b/test/unit/mux.c
@@ -1,7 +1,7 @@
 #include "emu/mux.h"
 #include "common.h"
 
-#define N 6
+#define N 10
 
 //static int
 //select_active_thread(struct mux *mux,
@@ -164,6 +164,44 @@ test_mid_propagate(struct mux *mux, int key)
 	check_output(mux, value_int64(new_value));
 }
 
+static void
+test_duplicate_output(struct mux *mux, int key1, int key2)
+{
+	int new_value = 2000 + key1;
+
+	struct mux_input *in1 = mux_find_input(mux, value_int64(key1));
+	if (in1 == NULL)
+		die("mux_find_input failed to locate input1 %d\n", key1);
+
+	struct mux_input *in2 = mux_find_input(mux, value_int64(key2));
+	if (in2 == NULL)
+		die("mux_find_input failed to locate input2 %d\n", key2);
+
+	if (chan_set(in1->chan, value_int64(new_value)) != 0)
+		die("chan_set failed\n");
+
+	if (chan_set(in2->chan, value_int64(new_value)) != 0)
+		die("chan_set failed\n");
+
+	/* Select input 1 */
+	if (chan_set(mux->select, value_int64(key1)) != 0)
+		die("chan_set failed\n");
+
+	if (bay_propagate(mux->bay) != 0)
+		die("bay_propagate failed\n");
+
+	check_output(mux, value_int64(new_value));
+
+	/* Now switch to input 2, which has the same value */
+	if (chan_set(mux->select, value_int64(key2)) != 0)
+		die("chan_set failed\n");
+
+	if (bay_propagate(mux->bay) != 0)
+		die("bay_propagate failed\n");
+
+	check_output(mux, value_int64(new_value));
+}
+
 
 int
 main(void)
@@ -212,6 +250,7 @@ main(void)
 	test_select_and_input(&mux, 3);
 	test_input_and_select(&mux, 4);
 	test_mid_propagate(&mux, 5);
+	test_duplicate_output(&mux, 6, 7);
 
 	err("OK\n");