(no commit message)

diff --git a/openpower/sv/cookbook/pospopcnt.mdwn b/openpower/sv/cookbook/pospopcnt.mdwn
index d28897169ab52a3f16d2ce5c7be0596536e20daf..d350ffae74399896d2bf27c1de6e0fa1f3adb473 100644 (file)
--- a/openpower/sv/cookbook/pospopcnt.mdwn
+++ b/openpower/sv/cookbook/pospopcnt.mdwn
@@ -1,6 +1,17 @@
-<https://bugs.libre-soc.org/show_bug.cgi?id=672>
+# Positional popcount SVP64
+
+* <https://bugs.libre-soc.org/show_bug.cgi?id=672>
+* <https://github.com/clausecker/pospop/blob/master/countsse2_amd64.s>
+
+Positional popcount in optimised assembler is typically done on SIMD ISAs in
+around 500 lines.  Power ISA thanks to `bpermd` can be much more efficient:
+with SVP64 even more so.  The reference implementation showing the concept
+is below, and it adds up the totals of each bit set to 1 in each bit-position,
+of an array of input alues.
 
 ```
+// Copyright (c) 2020 Robert Clausecker <fuz@fuz.su>
+// count8 reference implementation for tests.  Do not alter.
 func count8safe(counts *[8]int, buf []uint8) {
        for i := range buf {
                for j := 0; j < 8; j++ {
@@ -8,14 +19,6 @@ func count8safe(counts *[8]int, buf []uint8) {
                }
        }
 }
-
-func count16safe(counts *[16]int, buf []uint16) {
-       for i := range buf {
-               for j := 0; j < 16; j++ {
-                       counts[j] += int(buf[i] >> j & 1)
-               }
-       }
-}
 ```
 
 [[!tag svp64_cookbook ]]