It looks like there aren't actually users of this macro anywhere:

 * The kernel doesn't use it on x86 because we don't suppor ELF FDPIC.

 * The only Google results point to LMKL patches, both the one that
   wrote this (from 2010) and my patch to hide it behind __KERNEL__.

 * I grep'd through all the source tarballs on my machine, and the
   only packages that matched were the kernel and crui (which copied a
   PPC kernel header).

Since I'm not sure how to actually provide the right answer (if I
understand correctly, CONFIG_IA32_EMULATION is not __i386__), the only
thing I can think of to do is to just remove the definition.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Reviewed-by: Andrew Waterman <redacted>
Reviewed-by: Albert Ou <aou@eecs.berkeley.edu>
---
 arch/x86/include/uapi/asm/auxvec.h | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/include/uapi/asm/auxvec.h b/arch/x86/include/uapi/asm/auxvec.h
index 77203ac..1316b4c 100644
--- a/arch/x86/include/uapi/asm/auxvec.h
+++ b/arch/x86/include/uapi/asm/auxvec.h

@@ -9,11 +9,4 @@
 #endif
 #define AT_SYSINFO_EHDR		33
 
-/* entries in ARCH_DLINFO: */
-#if defined(CONFIG_IA32_EMULATION) || !defined(CONFIG_X86_64)
-# define AT_VECTOR_SIZE_ARCH 2
-#else /* else it's non-compat x86-64 */
-# define AT_VECTOR_SIZE_ARCH 1
-#endif
-
 #endif /* _ASM_X86_AUXVEC_H */

-- 
2.4.10