x86/hweight: Force inlining of __arch_hweight{32,64}()

With this config:

http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os

gcc-4.7.2 generates many copies of these tiny functions:

__arch_hweight32 (35 copies):
55 push %rbp
e8 66 9b 4a 00 callq __sw_hweight32
48 89 e5 mov %rsp,%rbp
5d pop %rbp
c3 retq

__arch_hweight64 (8 copies):
55 push %rbp
e8 5e c2 8a 00 callq __sw_hweight64
48 89 e5 mov %rsp,%rbp
5d pop %rbp
c3 retq

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122

This patch fixes this via s/inline/__always_inline/

To avoid touching 32-bit case where such change was not tested
to be a win, reformat __arch_hweight64() to have completely
disjoint 64-bit and 32-bit implementations. IOW: made #ifdef /
32 bits and 64 bits instead of having #ifdef / #else / #endif
inside a single function body. Only 64-bit __arch_hweight64() is
__always_inline'd.

text data bss dec filename
86971120 17195912 36659200 140826232 vmlinux.before
86970954 17195912 36659200 140826066 vmlinux

Signed-off-by: Denys Vlasenko <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Thomas Graf <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/include/asm/arch_hweight.h

···
  * ARCH_HWEIGHT_CFLAGS in <arch/x86/Kconfig> for the respective
  * compiler switches.
  */
-static inline unsigned int __arch_hweight32(unsigned int w)
+static __always_inline unsigned int __arch_hweight32(unsigned int w)
 {
 	unsigned int res = 0;
 
···
 	return __arch_hweight32(w & 0xff);
 }
 
+#ifdef CONFIG_X86_32
 static inline unsigned long __arch_hweight64(__u64 w)
+{
+	return  __arch_hweight32((u32)w) +
+		__arch_hweight32((u32)(w >> 32));
+}
+#else
+static __always_inline unsigned long __arch_hweight64(__u64 w)
 {
 	unsigned long res = 0;
 
-#ifdef CONFIG_X86_32
-	return  __arch_hweight32((u32)w) +
-		__arch_hweight32((u32)(w >> 32));
-#else
 	asm (ALTERNATIVE("call __sw_hweight64", POPCNT64, X86_FEATURE_POPCNT)
 		     : "="REG_OUT (res)
 		     : REG_IN (w));
-#endif /* CONFIG_X86_32 */
 
 	return res;
 }
+#endif /* CONFIG_X86_32 */
 
 #endif