A patch for Picodrive emulator to obtain all values that program counter had through the game that you were playing. Very handy for disassembling Sega Mega Drive / Genesis games. https://github.com/notaz/picodrive, commit 8cd962d14d7a866c69ebc82b9679a426c7709adb

picodrive-pc-trace-on-8cd962d14d7a866c69ebc82b9679a426c7709adb.patch

diff --git a/cpu/fame/famec.c b/cpu/fame/famec.c
index 9e832bc4..f598797a 100644
--- a/cpu/fame/famec.c
+++ b/cpu/fame/famec.c
@@ -222,8 +222,11 @@ https://github.com/notaz/picodrive, commit 8cd962d14d7a866c69ebc82b9679a426c7709adb
 #define ROR_32(A, C)    (LSR_32(A, C) | LSL_32(A, 32-(C)))
 #define ROR_33(A, C)    (LSR_32(A, C) | LSL_32(A, 33-(C)))
 
+extern void trace_pc(unsigned);
+
 #ifndef FAMEC_NO_GOTOS
 #define NEXT                    \
+    trace_pc((unsigned)((uintptr_t)PC - BasePC)); \
     FETCH_WORD(Opcode);         \
     goto *JumpTable[Opcode];
 
diff --git a/platform/common/emu.c b/platform/common/emu.c
index f371f5bc..7cbfb2cb 100644
--- a/platform/common/emu.c
+++ b/platform/common/emu.c
@@ -1171,6 +1171,40 @@ static void run_events_ui(unsigned int which)
 		engineState = PGS_Menu;
 }
 
+#define ROM_SIZE ((size_t)(4*1024*1024))
+static unsigned char pc_map[ROM_SIZE] = {0};
+
+#include <assert.h>
+#include <errno.h>
+
+void trace_pc(unsigned pc)
+{
+    assert(pc < ROM_SIZE);
+    pc_map[pc] = 1;
+}
+
+static void dump_pc(void)
+{
+    const char *file_name = "/tmp/trace.txt";
+    FILE *out = fopen(file_name, "w");
+    if (out == NULL) {
+        const int err = errno;
+        fprintf(
+                stderr,
+                "dump_pc: fopen(\"%s\", \"r\"): Error (%d): \"%s\"\n",
+                file_name,
+                err,
+                strerror(err));
+        return;
+    }
+    for (size_t i = 0; i < ROM_SIZE; i++) {
+        if (pc_map[i]) {
+            fprintf(out, "%zu\n", i);
+        }
+    }
+    fclose(out);
+}
+
 void emu_update_input(void)
 {
 	static int prev_events = 0;
@@ -1179,6 +1213,16 @@ void emu_update_input(void)
 	int events;
 
 	in_update(actions);
+    // F6 key
+    static int pressed_f6 = 0;
+    if ((actions[0] & 0x00100000) && !pressed_f6) {
+        pressed_f6 = 1;
+        printf("Pressed F6\n");
+    } else if (!(actions[0] & 0x00100000) && pressed_f6) {
+        pressed_f6 = 0;
+        printf("Released F6\n");
+        dump_pc();
+    }
 
 	pl_actions[0] = actions[IN_BINDTYPE_PLAYER12];
 	pl_actions[1] = actions[IN_BINDTYPE_PLAYER12] >> 16;