linux/arch/x86_64
David Howells f0d1b0b30d [PATCH] LOG2: Implement a general integer log2 facility in the kernel
This facility provides three entry points:

	ilog2()		Log base 2 of unsigned long
	ilog2_u32()	Log base 2 of u32
	ilog2_u64()	Log base 2 of u64

These facilities can either be used inside functions on dynamic data:

	int do_something(long q)
	{
		...;
		y = ilog2(x)
		...;
	}

Or can be used to statically initialise global variables with constant values:

	unsigned n = ilog2(27);

When performing static initialisation, the compiler will report "error:
initializer element is not constant" if asked to take a log of zero or of
something not reducible to a constant.  They treat negative numbers as
unsigned.

When not dealing with a constant, they fall back to using fls() which permits
them to use arch-specific log calculation instructions - such as BSR on
x86/x86_64 or SCAN on FRV - if available.

[akpm@osdl.org: MMC fix]
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Howells <dhowells@redhat.com>
Cc: Wojtek Kaniewski <wojtekka@toxygen.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:28:51 -08:00
..
boot [PATCH] x86-64: shorten the x86_64 boot setup GDT to what the comment says 2006-11-14 16:57:46 +01:00
crypto [CRYPTO] api: Get rid of flags argument to setkey 2006-09-21 11:41:02 +10:00
ia32 [PATCH] x86_64: change uses of f_{dentry, vfsmnt} to use f_path 2006-12-08 08:28:42 -08:00
kernel [PATCH] Generic BUG for x86-64 2006-12-08 08:28:39 -08:00
lib [PATCH] x86-64: Don't force inlining of do_csum 2006-12-07 02:14:07 +01:00
mm [PATCH] x86-64: fix perms/range of vsyscall vma in /proc/*/maps 2006-12-07 02:14:09 +01:00
oprofile [PATCH] Move Kprobes and Oprofile to "Instrumentation Support" menu 2005-11-07 07:53:35 -08:00
pci Revert "[PATCH] MMCONFIG and new Intel motherboards" 2006-11-14 16:56:33 +01:00
defconfig [PATCH] x86-64: Update defconfig 2006-12-07 02:14:00 +01:00
Kconfig [PATCH] LOG2: Implement a general integer log2 facility in the kernel 2006-12-08 08:28:51 -08:00
Kconfig.debug [PATCH] lockdep: irqtrace subsystem, x86_64 support 2006-07-03 15:27:03 -07:00
Makefile [PATCH] x86-64: Add option to compile for Core2 2006-12-07 02:14:09 +01:00