x86 guest/host: do SSE comparisons.  

To make this easier, add to IRConst a new kind of literal -- 
a 128-bit literal specified by a 16-bit value.  Each bit of the
latter is defines one byte of the 128-bit value, either 0x00 or
0xFF.



git-svn-id: svn://svn.valgrind.org/vex/trunk@605 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/host-generic/h_generic_regs.h b/priv/host-generic/h_generic_regs.h
index 3ea1b73..8208e82 100644
--- a/priv/host-generic/h_generic_regs.h
+++ b/priv/host-generic/h_generic_regs.h
@@ -77,6 +77,11 @@
    selectors can speak about.  We would not expect all of them to be
    available on any specific host.  For example on x86, the available
    classes are: Int32, Flt64, Vec128 only.
+
+   IMPORTANT NOTE: Vec128 is the only >= 128-bit-sized class, and
+   reg_alloc2.c handles it specially when assigning spill slots.  If
+   you add another 128-bit or larger regclass, you must remember to
+   update reg_alloc2.c accordingly.
 */
 typedef
    enum {