[PATCH 4/12] generic fls() and fls64()

From: Akinobu Mita <mita_at_miraclelinux.com>
Date: 2006-01-26 14:32:36
This patch introduces the C-language equivalent of the function:
int fls(int x);
int fls64(__u64 x);

HAVE_ARCH_FLS_BITOPS is defined when the architecture has its own
fls().
HAVE_ARCH_FLS64_BITOPS is defined when the architecture has its own
fls64()

This code largely copied from:
include/linux/bitops.h


Index: 2.6-git/include/asm-generic/bitops.h
===================================================================
--- 2.6-git.orig/include/asm-generic/bitops.h	2006-01-25 19:14:10.000000000 +0900
+++ 2.6-git/include/asm-generic/bitops.h	2006-01-25 19:14:10.000000000 +0900
@@ -237,12 +237,54 @@
 
 #endif /* HAVE_ARCH_FFZ_BITOPS */
 
+#ifndef HAVE_ARCH_FLS_BITOPS
+
 /*
  * fls: find last bit set.
  */
 
-#define fls(x) generic_fls(x)
-#define fls64(x)   generic_fls64(x)
+static __inline__ int fls(int x)
+{
+	int r = 32;
+
+	if (!x)
+		return 0;
+	if (!(x & 0xffff0000u)) {
+		x <<= 16;
+		r -= 16;
+	}
+	if (!(x & 0xff000000u)) {
+		x <<= 8;
+		r -= 8;
+	}
+	if (!(x & 0xf0000000u)) {
+		x <<= 4;
+		r -= 4;
+	}
+	if (!(x & 0xc0000000u)) {
+		x <<= 2;
+		r -= 2;
+	}
+	if (!(x & 0x80000000u)) {
+		x <<= 1;
+		r -= 1;
+	}
+	return r;
+}
+
+#endif /* HAVE_ARCH_FLS_BITOPS */
+
+#ifndef HAVE_ARCH_FLS64_BITOPS
+
+static inline int fls64(__u64 x)
+{
+	__u32 h = x >> 32;
+	if (h)
+		return fls(x) + 32;
+	return fls(x);
+}
+
+#endif /* HAVE_ARCH_FLS64_BITOPS */
 
 #ifdef __KERNEL__
 
-
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Received on Thu Jan 26 14:32:58 2006

This archive was generated by hypermail 2.1.8 : 2006-01-26 14:34:06 EST