Added a note in response to external feedback.
diff --git a/docs/porting-guide.html b/docs/porting-guide.html
index 8a05caa..fd028cc 100644
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@@ -334,6 +334,12 @@
that you are testing the basic form of the instruction, add the
<code>--no-optimize</code> option.
</p><p>
+There is no in-built instruction tracing mechanism. If you want
+to know for sure that your implementation of an opcode handler
+is being used, the easiest approach is to insert a "printf"
+call. For an example, look at <code>common_squeak</code> in
+<code>dalvik/vm/mterp/armv5te/footer.S</code>.
+</p><p>
At some point you need to ensure that debuggers and profiling work with
your interpreter. The easiest way to do this is to simply connect a
debugger or toggle profiling. (A future test suite may include some
