From 90fc44ecfa4741a055ec3d35722e2624c2231f98 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 4 Jul 2018 09:07:23 +0100
Subject: Optimize std::rotl and std::rotr, add test for std::popcount

	* include/std/bit (__rotl, __rotr): Avoid branch.
	(_If_is_unsigned_integer): Use remove_cv_t.
	* testsuite/26_numerics/bit/bitops.count/popcount.cc: New.

From-SVN: r262378
---
 libstdc++-v3/include/std/bit | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

(limited to 'libstdc++-v3/include/std/bit')

diff --git a/libstdc++-v3/include/std/bit b/libstdc++-v3/include/std/bit
index 76aa095..ace8895 100644
--- a/libstdc++-v3/include/std/bit
+++ b/libstdc++-v3/include/std/bit
@@ -46,9 +46,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       constexpr auto _Nd = numeric_limits<_Tp>::digits;
       const unsigned __sN = __s % _Nd;
-      if (__sN)
-        return (__x << __sN) | (__x >> (_Nd - __sN));
-      return __x;
+      return (__x << __sN) | (__x >> ((-__sN) % _Nd));
     }
 
   template<typename _Tp>
@@ -57,9 +55,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       constexpr auto _Nd = numeric_limits<_Tp>::digits;
       const unsigned __sN = __s % _Nd;
-      if (__sN)
-        return (__x >> __sN) | (__x << (_Nd - __sN));
-      return __x;
+      return (__x >> __sN) | (__x << ((-__sN) % _Nd));
     }
 
   template<typename _Tp>
@@ -237,7 +233,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   template<typename _Tp, typename _Up = _Tp>
     using _If_is_unsigned_integer
-      = typename _If_is_unsigned_integer_type<_Tp, _Up>::type;
+      = typename _If_is_unsigned_integer_type<remove_cv_t<_Tp>, _Up>::type;
 
 #if ! __STRICT_ANSI__
   // [bitops.rot], rotating
-- 
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