From 2e3050c98994a4f4792839a3a1e1f294b24ba363 Mon Sep 17 00:00:00 2001
From: Jack Lloyd <jack@randombit.net>
Date: Sun, 15 Apr 2018 17:45:47 -0400
Subject: Use GCC builtins for clz operation

---
 src/lib/utils/bit_ops.h | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

(limited to 'src/lib/utils')

diff --git a/src/lib/utils/bit_ops.h b/src/lib/utils/bit_ops.h
index aa41db391..c7e401492 100644
--- a/src/lib/utils/bit_ops.h
+++ b/src/lib/utils/bit_ops.h
@@ -107,11 +107,36 @@ inline size_t ctz(T n)
 template<>
 inline size_t ctz(uint32_t n)
    {
+   if(n == 0)
+      return 32;
    return __builtin_ctz(n);
    }
 
-#endif
+template<>
+inline size_t ctz(uint64_t n)
+   {
+   if(n == 0)
+      return 64;
+   return __builtin_ctzll(n);
+   }
 
+template<>
+inline size_t high_bit(uint32_t x)
+   {
+   if(x == 0)
+      return 0;
+   return (32 - __builtin_clz(x));
+   }
+
+template<>
+inline size_t high_bit(uint64_t x)
+   {
+   if(x == 0)
+      return 0;
+   return (64 - __builtin_clzll(x));
+   }
+
+#endif
 
 template<typename T>
 size_t ceil_log2(T x)
-- 
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