From d1cc45f22368205b3de4c4aed8d9de4fe7d155e7 Mon Sep 17 00:00:00 2001
From: Alexandre Duret-Lutz <adl@lrde.epita.fr>
Date: Sun, 17 Jan 2021 16:00:16 +0100
Subject: [PATCH] clz: inline the implementation

__builtin_clz() can be implemented with two x86 instructions, so we
don't want to hide it behind a function call.

* spot/misc/clz.cc: Delete the implementation.
* spot/misc/Makefile.am: Delete clz.cc.
* spot/misc/clz.hh: Make the implementation public.
---
 spot/misc/Makefile.am |   5 +-
 spot/misc/clz.cc      | 115 ------------------------------------------
 spot/misc/clz.hh      |  35 +++++++++++--
 3 files changed, 33 insertions(+), 122 deletions(-)
 delete mode 100644 spot/misc/clz.cc

diff --git a/spot/misc/Makefile.am b/spot/misc/Makefile.am
index 7f2aa835f..e509dbe87 100644
--- a/spot/misc/Makefile.am
+++ b/spot/misc/Makefile.am
@@ -1,6 +1,6 @@
 ## -*- coding: utf-8 -*-
-## Copyright (C) 2011-2014, 2016-2018, 2020 Laboratoire de Recherche
-## et Développement de l'Epita (LRDE).
+## Copyright (C) 2011-2014, 2016-2018, 2020-2021 Laboratoire de
+## Recherche et Développement de l'Epita (LRDE).
 ## Copyright (C) 2003, 2004, 2005, 2006 Laboratoire d'Informatique de
 ## Paris 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
 ## Université Pierre et Marie Curie.
@@ -63,7 +63,6 @@ libmisc_la_SOURCES = \
   bareword.cc \
   bitset.cc \
   bitvect.cc \
-  clz.cc \
   escape.cc \
   formater.cc \
   intvcomp.cc \
diff --git a/spot/misc/clz.cc b/spot/misc/clz.cc
deleted file mode 100644
index 6b2173501..000000000
--- a/spot/misc/clz.cc
+++ /dev/null
@@ -1,115 +0,0 @@
-// -*- coding: utf-8 -*-
-// Copyright (C) 2018 Laboratoire de Recherche et Développement
-// de l'Epita (LRDE).
-//
-// This file is part of Spot, a model checking library.
-//
-// Spot is free software; you can redistribute it and/or modify it
-// under the terms of the GNU General Public License as published by
-// the Free Software Foundation; either version 3 of the License, or
-// (at your option) any later version.
-//
-// Spot is distributed in the hope that it will be useful, but WITHOUT
-// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
-// License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-#include "config.h"
-#include <spot/misc/clz.hh>
-
-namespace spot
-{
-  // use gcc and clang built-in functions
-  // both compilers use the same function names, and define __GNUC__
-#if __GNUC__
-  template<class T>
-  struct _clz;
-
-  template<>
-  struct _clz<unsigned>
-  {
-    unsigned
-    operator()(unsigned n) const noexcept
-    {
-      return __builtin_clz(n);
-    }
-  };
-
-  template<>
-  struct _clz<unsigned long>
-  {
-    unsigned long
-    operator()(unsigned long n) const noexcept
-    {
-      return __builtin_clzl(n);
-    }
-  };
-
-  template<>
-  struct _clz<unsigned long long>
-  {
-    unsigned long long
-    operator()(unsigned long long n) const noexcept
-    {
-      return __builtin_clzll(n);
-    }
-  };
-
-  size_t
-  clz(unsigned n)
-  {
-    return _clz<unsigned>()(n);
-  }
-
-  size_t
-  clz(unsigned long n)
-  {
-    return _clz<unsigned long>()(n);
-  }
-
-  size_t
-  clz(unsigned long long n)
-  {
-    return _clz<unsigned long long>()(n);
-  }
-#else
-  size_t
-  clz(unsigned n)
-  {
-    size_t res = CHAR_BIT*sizeof(size_t);
-    while (n)
-      {
-        --res;
-        n >>= 1;
-      }
-    return res;
-  }
-
-  size_t
-  clz(unsigned long n)
-  {
-    size_t res = CHAR_BIT*sizeof(unsigned long);
-    while (n)
-      {
-        --res;
-        n >>= 1;
-      }
-    return res;
-  }
-
-  size_t
-  clz(unsigned long long n)
-  {
-    size_t res = CHAR_BIT*sizeof(unsigned long long);
-    while (n)
-      {
-        --res;
-        n >>= 1;
-      }
-    return res;
-  }
-#endif
-}
diff --git a/spot/misc/clz.hh b/spot/misc/clz.hh
index 5b3d674c7..648b6615c 100644
--- a/spot/misc/clz.hh
+++ b/spot/misc/clz.hh
@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2018 Laboratoire de Recherche et Développement
+// Copyright (C) 2018, 2021 Laboratoire de Recherche et Développement
 // de l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
@@ -25,9 +25,36 @@
 
 namespace spot
 {
-  SPOT_API size_t clz(unsigned n);
+  template<typename Type,
+           typename = std::enable_if_t<std::is_unsigned<Type>::value>>
+  inline constexpr unsigned clz(Type n) noexcept
+  {
+    unsigned res = CHAR_BIT * sizeof(Type);
+    while (n)
+      {
+        --res;
+        n >>= 1;
+      }
+    return res;
+  }
 
-  SPOT_API size_t clz(unsigned long n);
+#if __GNUC__
+  template<>
+  inline constexpr unsigned clz(unsigned n) noexcept
+  {
+    return __builtin_clz(n);
+  }
 
-  SPOT_API size_t clz(unsigned long long n);
+  template<>
+  inline constexpr unsigned clz(unsigned long n) noexcept
+  {
+    return __builtin_clzl(n);
+  }
+
+  template<>
+  inline constexpr unsigned clz(unsigned long long n) noexcept
+  {
+    return __builtin_clzll(n);
+  }
+#endif
 }