(no commit message)

diff --git a/openpower/sv/SimpleV_rationale.mdwn b/openpower/sv/SimpleV_rationale.mdwn
index 1b72d8d69f050612f999a1518e1c55f688cc4115..727e2d9f6c951805b8569a652454979fb41e200b 100644 (file)
--- a/openpower/sv/SimpleV_rationale.mdwn
+++ b/openpower/sv/SimpleV_rationale.mdwn
@@ -321,7 +321,19 @@ a decade ago after the Packed SIMD variants were considered to be
 duplicates.  With it being completely inappropriate to attempt to Vectorise
 a Packed SIMD ISA designed 20 years ago with no Predication of any kind,
 the Scalar ISA, a much better all-round candidate for Vectorisation is
-left anaemic.  Fortunately, with the ISA Working Group being willing
+left anaemic.
+
+A particular key instruction that is missing is `MV.X` which is
+illustrated as `GPR(dest) = GPR(GPR(src))`. This horrendously
+expensive instruction is almost never added to a Scalar ISA but
+is almost always added to a Vector one, it allows for arbitrary
+remapping of elements within a Vector to positions specified
+by another Vector. A typical Scalar ISA will use Memory to
+achieve this task, but with Vector ISAs the Vector Register Files are
+usually so enormous, and so far away from Memory, that it is easier and
+more efficient, architecturally, to provide these Indexing instructions.
+
+Fortunately, with the ISA Working Group being willing
 to consider RFCs (Requests For Change) these omissions have the potential
 to be corrected.