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-rw-r--r--lib/clzti2.c32
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diff --git a/lib/clzti2.c b/lib/clzti2.c
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+//===-- clzti2.c - Implement __clzti2 -------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __clzti2 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#if __x86_64
+
+#include "int_lib.h"
+
+// Returns: the number of leading 0-bits
+
+// Precondition: a != 0
+
+si_int
+__clzti2(ti_int a)
+{
+ twords x;
+ x.all = a;
+ const di_int f = -(x.high == 0);
+ return __builtin_clzll((x.high & ~f) | (x.low & f)) +
+ ((si_int)f & ((si_int)(sizeof(di_int) * CHAR_BIT)));
+}
+
+#endif