This series introduces fast paths for find_bit() routines. It is beneficial for typical systems, but those who limited in I-cache may be concerned about increasing the .text size of the Image. To address this concern, one can disable FAST_PATH option in the config and some save memory. The effect of this option on my arm64 next-20210217 build is: Before: Sections: Idx Name Size VMA LMA File off Algn 0 .head.text 00010000 ffff800010000000 ffff800010000000 00010000 2**16 CONTENTS, ALLOC, LOAD, READONLY, CODE 1 .text 0115e3a8 ffff800010010000 ffff800010010000 00020000 2**16 CONTENTS, ALLOC, LOAD, READONLY, CODE 2 .got.plt 00000018 ffff80001116e3a8 ffff80001116e3a8 0117e3a8 2**3 CONTENTS, ALLOC, LOAD, DATA 3 .rodata 007a72ca ffff800011170000 ffff800011170000 01180000 2**12 CONTENTS, ALLOC, LOAD, DATA ... After: Sections: Idx Name Size VMA LMA File off Algn 0 .head.text 00010000 ffff800010000000 ffff800010000000 00010000 2**16 CONTENTS, ALLOC, LOAD, READONLY, CODE 1 .text 011623a8 ffff800010010000 ffff800010010000 00020000 2**16 CONTENTS, ALLOC, LOAD, READONLY, CODE 2 .got.plt 00000018 ffff8000111723a8 ffff8000111723a8 011823a8 2**3 CONTENTS, ALLOC, LOAD, DATA 3 .rodata 007a772a ffff800011180000 ffff800011180000 01190000 2**12 CONTENTS, ALLOC, LOAD, DATA ... Notice that this is the cumulive effect on already existing fast paths controlled by SMALL_CONST() together with ones added by this series. Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx> --- include/asm-generic/bitsperlong.h | 4 ++++ lib/Kconfig | 7 +++++++ 2 files changed, 11 insertions(+) diff --git a/include/asm-generic/bitsperlong.h b/include/asm-generic/bitsperlong.h index 0eeb77544f1d..209e531074c1 100644 --- a/include/asm-generic/bitsperlong.h +++ b/include/asm-generic/bitsperlong.h @@ -23,6 +23,10 @@ #define BITS_PER_LONG_LONG 64 #endif +#ifdef CONFIG_FAST_PATH #define SMALL_CONST(n) (__builtin_constant_p(n) && (unsigned long)(n) < BITS_PER_LONG) +#else +#define SMALL_CONST(n) (0) +#endif #endif /* __ASM_GENERIC_BITS_PER_LONG */ diff --git a/lib/Kconfig b/lib/Kconfig index a38cc61256f1..7a1b9c8d2a32 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -39,6 +39,13 @@ config PACKING When in doubt, say N. +config FAST_PATH + bool "Enable fast path code generation" + default y + help + This option enables fast path optimization with the cost of increasing + the text section. + config BITREVERSE tristate -- 2.25.1
