[PATCH] LOG2: Provide ilog2() fallbacks for powerpc

Provide ilog2() fallbacks for powerpc for 32-bit numbers and 64-bit numbers on
ppc64.

Signed-off-by: David Howells <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/powerpc/Kconfig

···
 
 config ARCH_HAS_ILOG2_U32
 	bool
-	default n
+	default y
 
 config ARCH_HAS_ILOG2_U64
 	bool
-	default n
+	default y if 64BIT
 
 config GENERIC_HWEIGHT
 	bool

include/asm-powerpc/bitops.h

···
  * Return the zero-based bit position (LE, not IBM bit numbering) of
  * the most significant 1-bit in a double word.
  */
-static __inline__ int __ilog2(unsigned long x)
+static __inline__ __attribute__((const))
+int __ilog2(unsigned long x)
 {
 	int lz;
 
 	asm (PPC_CNTLZL "%0,%1" : "=r" (lz) : "r" (x));
 	return BITS_PER_LONG - 1 - lz;
 }
+
+static inline __attribute__((const))
+int __ilog2_u32(u32 n)
+{
+	int bit;
+	asm ("cntlzw %0,%1" : "=r" (bit) : "r" (n));
+	return 31 - bit;
+}
+
+#ifdef __powerpc64__
+static inline __attribute__((const))
+int __ilog2_u64(u32 n)
+{
+	int bit;
+	asm ("cntlzd %0,%1" : "=r" (bit) : "r" (n));
+	return 63 - bit;
+}
+#endif
 
 /*
  * Determines the bit position of the least significant 0 bit in the

include/asm-powerpc/page_32.h

···
 static inline void clear_page(void *page) { clear_pages(page, 0); }
 extern void copy_page(void *to, void *from);
 
-/* Pure 2^n version of get_order */
-extern __inline__ int get_order(unsigned long size)
-{
-	int lz;
-
-	size = (size-1) >> PAGE_SHIFT;
-	asm ("cntlzw %0,%1" : "=r" (lz) : "r" (size));
-	return 32 - lz;
-}
+#include <asm-generic/page.h>
 
 #endif /* __ASSEMBLY__ */