Merge tag 'byteswap-for-linus-20121219' of git://git.infradead.org/users/dwmw2/byteswap

[karo-tx-linux.git] / arch / Kconfig

diff --git a/arch/Kconfig b/arch/Kconfig
index 34884faf98cd26f3f24c6483dd98b10855387232..8e9e3246b2b4e0f1a0b2218f5e49a8cacecb24d2 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -80,6 +80,7 @@ config UPROBES
        bool "Transparent user-space probes (EXPERIMENTAL)"
        depends on UPROBE_EVENT && PERF_EVENTS
        default n
+       select PERCPU_RWSEM
        help
          Uprobes is the user-space counterpart to kprobes: they
          enable instrumentation applications (such as 'perf probe')
@@ -112,6 +113,25 @@ config HAVE_EFFICIENT_UNALIGNED_ACCESS
          See Documentation/unaligned-memory-access.txt for more
          information on the topic of unaligned memory accesses.
 
+config ARCH_USE_BUILTIN_BSWAP
+       bool
+       help
+        Modern versions of GCC (since 4.4) have builtin functions
+        for handling byte-swapping. Using these, instead of the old
+        inline assembler that the architecture code provides in the
+        __arch_bswapXX() macros, allows the compiler to see what's
+        happening and offers more opportunity for optimisation. In
+        particular, the compiler will be able to combine the byteswap
+        with a nearby load or store and use load-and-swap or
+        store-and-swap instructions if the architecture has them. It
+        should almost *never* result in code which is worse than the
+        hand-coded assembler in <asm/swab.h>.  But just in case it
+        does, the use of the builtins is optional.
+
+        Any architecture with load-and-swap or store-and-swap
+        instructions should set this. And it shouldn't hurt to set it
+        on architectures that don't have such instructions.
+
 config HAVE_SYSCALL_WRAPPERS
        bool