diff options
Diffstat (limited to 'include/linux/unroll.h')
| -rw-r--r-- | include/linux/unroll.h | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/include/linux/unroll.h b/include/linux/unroll.h index d42fd6366373..863fb69f6a7e 100644 --- a/include/linux/unroll.h +++ b/include/linux/unroll.h @@ -9,6 +9,50 @@ #include <linux/args.h> +#ifdef CONFIG_CC_IS_CLANG +#define __pick_unrolled(x, y) _Pragma(#x) +#elif CONFIG_GCC_VERSION >= 80000 +#define __pick_unrolled(x, y) _Pragma(#y) +#else +#define __pick_unrolled(x, y) /* not supported */ +#endif + +/** + * unrolled - loop attributes to ask the compiler to unroll it + * + * Usage: + * + * #define BATCH 8 + * + * unrolled_count(BATCH) + * for (u32 i = 0; i < BATCH; i++) + * // loop body without cross-iteration dependencies + * + * This is only a hint and the compiler is free to disable unrolling if it + * thinks the count is suboptimal and may hurt performance and/or hugely + * increase object code size. + * Not having any cross-iteration dependencies (i.e. when iter x + 1 depends + * on what iter x will do with variables) is not a strict requirement, but + * provides best performance and object code size. + * Available only on Clang and GCC 8.x onwards. + */ + +/* Ask the compiler to pick an optimal unroll count, Clang only */ +#define unrolled \ + __pick_unrolled(clang loop unroll(enable), /* nothing */) + +/* Unroll each @n iterations of the loop */ +#define unrolled_count(n) \ + __pick_unrolled(clang loop unroll_count(n), GCC unroll n) + +/* Unroll the whole loop */ +#define unrolled_full \ + __pick_unrolled(clang loop unroll(full), GCC unroll 65534) + +/* Never unroll the loop */ +#define unrolled_none \ + __pick_unrolled(clang loop unroll(disable), GCC unroll 1) + #define UNROLL(N, MACRO, args...) CONCATENATE(__UNROLL_, N)(MACRO, args) #define __UNROLL_0(MACRO, args...) |