From 81cc31eaa95165d4238f563a1dfe688740f35d90 Mon Sep 17 00:00:00 2001
From: Alan Donovan <adonovan@google.com>
Date: Wed, 1 Mar 2017 14:50:34 +0000
Subject: [PATCH] Revert "x/tools/container/intsets: remove unused function"

This reverts commit 79902b439b3ef4c163ff5e96ac1f282f31c8a131.

Reason for revert: build broken on some platforms.

Change-Id: I5ceddc305580ff97f47ae27da831f99e96dab424
Reviewed-on: https://go-review.googlesource.com/37539
Reviewed-by: David R. Jenni <david.r.jenni@gmail.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
---
 container/intsets/util.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/container/intsets/util.go b/container/intsets/util.go
index 6710278170..dd1db86b1c 100644
--- a/container/intsets/util.go
+++ b/container/intsets/util.go
@@ -4,6 +4,16 @@
 
 package intsets
 
+// From Hacker's Delight, fig 5.2.
+func popcountHD(x uint32) int {
+	x -= (x >> 1) & 0x55555555
+	x = (x & 0x33333333) + ((x >> 2) & 0x33333333)
+	x = (x + (x >> 4)) & 0x0f0f0f0f
+	x = x + (x >> 8)
+	x = x + (x >> 16)
+	return int(x & 0x0000003f)
+}
+
 var a [1 << 8]byte
 
 func init() {