simplified <code>getRegister</code> scheme described above, in which
<code>iselExpr64</code>generates its results into two vregs which
can always safely be modified afterwards.
-
+<p>
Virtual registers are, unsurprisingly, distinguished by their
<code>Unique</code>s. There is a small difficulty in how to
know what the vreg for the upper 32 bits of a value is, given the vreg
comment in the code.
+<h3>Duplicate implementation for many STG macros</h3>
+
+This has been discussed at length already. It has caused a couple of
+nasty bugs due to subtle untracked divergence in the macro
+translations. The macro-expander really should be pushed up into the
+Abstract C phase, so the problem can't happen.
+<p>
+Doing so would have the added benefit that the NCG could be used to
+compile more "ways" -- well, at least the 'p' profiling way.
+
<h3>How to debug the NCG without losing your sanity/hair/cool</h3>