diff options
Diffstat (limited to 'arch/Kconfig')
| -rw-r--r-- | arch/Kconfig | 19 |
1 files changed, 8 insertions, 11 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 61130b88964b..31220f512b16 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -232,17 +232,14 @@ config HAVE_EFFICIENT_UNALIGNED_ACCESS 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. + GCC and Clang have builtin functions for handling byte-swapping. + Using these 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 |