mirror of https://gitee.com/openkylin/linux.git
78 lines
3.0 KiB
C
78 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
|
|
#ifndef __ASM_UNROLL_H__
|
|
#define __ASM_UNROLL_H__
|
|
|
|
/*
|
|
* Explicitly unroll a loop, for use in cases where doing so is performance
|
|
* critical.
|
|
*
|
|
* Ideally we'd rely upon the compiler to provide this but there's no commonly
|
|
* available means to do so. For example GCC's "#pragma GCC unroll"
|
|
* functionality would be ideal but is only available from GCC 8 onwards. Using
|
|
* -funroll-loops is an option but GCC tends to make poor choices when
|
|
* compiling our string functions. -funroll-all-loops leads to massive code
|
|
* bloat, even if only applied to the string functions.
|
|
*/
|
|
#define unroll(times, fn, ...) do { \
|
|
extern void bad_unroll(void) \
|
|
__compiletime_error("Unsupported unroll"); \
|
|
\
|
|
/* \
|
|
* We can't unroll if the number of iterations isn't \
|
|
* compile-time constant. Unfortunately GCC versions \
|
|
* up until 4.6 tend to miss obvious constants & cause \
|
|
* this check to fail, even though they go on to \
|
|
* generate reasonable code for the switch statement, \
|
|
* so we skip the sanity check for those compilers. \
|
|
*/ \
|
|
BUILD_BUG_ON((CONFIG_GCC_VERSION >= 40700 || \
|
|
CONFIG_CLANG_VERSION >= 80000) && \
|
|
!__builtin_constant_p(times)); \
|
|
\
|
|
switch (times) { \
|
|
case 32: fn(__VA_ARGS__); /* fall through */ \
|
|
case 31: fn(__VA_ARGS__); /* fall through */ \
|
|
case 30: fn(__VA_ARGS__); /* fall through */ \
|
|
case 29: fn(__VA_ARGS__); /* fall through */ \
|
|
case 28: fn(__VA_ARGS__); /* fall through */ \
|
|
case 27: fn(__VA_ARGS__); /* fall through */ \
|
|
case 26: fn(__VA_ARGS__); /* fall through */ \
|
|
case 25: fn(__VA_ARGS__); /* fall through */ \
|
|
case 24: fn(__VA_ARGS__); /* fall through */ \
|
|
case 23: fn(__VA_ARGS__); /* fall through */ \
|
|
case 22: fn(__VA_ARGS__); /* fall through */ \
|
|
case 21: fn(__VA_ARGS__); /* fall through */ \
|
|
case 20: fn(__VA_ARGS__); /* fall through */ \
|
|
case 19: fn(__VA_ARGS__); /* fall through */ \
|
|
case 18: fn(__VA_ARGS__); /* fall through */ \
|
|
case 17: fn(__VA_ARGS__); /* fall through */ \
|
|
case 16: fn(__VA_ARGS__); /* fall through */ \
|
|
case 15: fn(__VA_ARGS__); /* fall through */ \
|
|
case 14: fn(__VA_ARGS__); /* fall through */ \
|
|
case 13: fn(__VA_ARGS__); /* fall through */ \
|
|
case 12: fn(__VA_ARGS__); /* fall through */ \
|
|
case 11: fn(__VA_ARGS__); /* fall through */ \
|
|
case 10: fn(__VA_ARGS__); /* fall through */ \
|
|
case 9: fn(__VA_ARGS__); /* fall through */ \
|
|
case 8: fn(__VA_ARGS__); /* fall through */ \
|
|
case 7: fn(__VA_ARGS__); /* fall through */ \
|
|
case 6: fn(__VA_ARGS__); /* fall through */ \
|
|
case 5: fn(__VA_ARGS__); /* fall through */ \
|
|
case 4: fn(__VA_ARGS__); /* fall through */ \
|
|
case 3: fn(__VA_ARGS__); /* fall through */ \
|
|
case 2: fn(__VA_ARGS__); /* fall through */ \
|
|
case 1: fn(__VA_ARGS__); /* fall through */ \
|
|
case 0: break; \
|
|
\
|
|
default: \
|
|
/* \
|
|
* Either the iteration count is unreasonable \
|
|
* or we need to add more cases above. \
|
|
*/ \
|
|
bad_unroll(); \
|
|
break; \
|
|
} \
|
|
} while (0)
|
|
|
|
#endif /* __ASM_UNROLL_H__ */
|