18c2ecf20Sopenharmony_ci/* SPDX-License-Identifier: GPL-2.0-only */ 28c2ecf20Sopenharmony_ci#ifndef __ASM_UNROLL_H__ 38c2ecf20Sopenharmony_ci#define __ASM_UNROLL_H__ 48c2ecf20Sopenharmony_ci 58c2ecf20Sopenharmony_ci/* 68c2ecf20Sopenharmony_ci * Explicitly unroll a loop, for use in cases where doing so is performance 78c2ecf20Sopenharmony_ci * critical. 88c2ecf20Sopenharmony_ci * 98c2ecf20Sopenharmony_ci * Ideally we'd rely upon the compiler to provide this but there's no commonly 108c2ecf20Sopenharmony_ci * available means to do so. For example GCC's "#pragma GCC unroll" 118c2ecf20Sopenharmony_ci * functionality would be ideal but is only available from GCC 8 onwards. Using 128c2ecf20Sopenharmony_ci * -funroll-loops is an option but GCC tends to make poor choices when 138c2ecf20Sopenharmony_ci * compiling our string functions. -funroll-all-loops leads to massive code 148c2ecf20Sopenharmony_ci * bloat, even if only applied to the string functions. 158c2ecf20Sopenharmony_ci */ 168c2ecf20Sopenharmony_ci#define unroll(times, fn, ...) do { \ 178c2ecf20Sopenharmony_ci extern void bad_unroll(void) \ 188c2ecf20Sopenharmony_ci __compiletime_error("Unsupported unroll"); \ 198c2ecf20Sopenharmony_ci \ 208c2ecf20Sopenharmony_ci /* \ 218c2ecf20Sopenharmony_ci * We can't unroll if the number of iterations isn't \ 228c2ecf20Sopenharmony_ci * compile-time constant. Unfortunately clang versions \ 238c2ecf20Sopenharmony_ci * up until 8.0 tend to miss obvious constants & cause \ 248c2ecf20Sopenharmony_ci * this check to fail, even though they go on to \ 258c2ecf20Sopenharmony_ci * generate reasonable code for the switch statement, \ 268c2ecf20Sopenharmony_ci * so we skip the sanity check for those compilers. \ 278c2ecf20Sopenharmony_ci */ \ 288c2ecf20Sopenharmony_ci BUILD_BUG_ON(!__builtin_constant_p(times)); \ 298c2ecf20Sopenharmony_ci \ 308c2ecf20Sopenharmony_ci switch (times) { \ 318c2ecf20Sopenharmony_ci case 32: fn(__VA_ARGS__); fallthrough; \ 328c2ecf20Sopenharmony_ci case 31: fn(__VA_ARGS__); fallthrough; \ 338c2ecf20Sopenharmony_ci case 30: fn(__VA_ARGS__); fallthrough; \ 348c2ecf20Sopenharmony_ci case 29: fn(__VA_ARGS__); fallthrough; \ 358c2ecf20Sopenharmony_ci case 28: fn(__VA_ARGS__); fallthrough; \ 368c2ecf20Sopenharmony_ci case 27: fn(__VA_ARGS__); fallthrough; \ 378c2ecf20Sopenharmony_ci case 26: fn(__VA_ARGS__); fallthrough; \ 388c2ecf20Sopenharmony_ci case 25: fn(__VA_ARGS__); fallthrough; \ 398c2ecf20Sopenharmony_ci case 24: fn(__VA_ARGS__); fallthrough; \ 408c2ecf20Sopenharmony_ci case 23: fn(__VA_ARGS__); fallthrough; \ 418c2ecf20Sopenharmony_ci case 22: fn(__VA_ARGS__); fallthrough; \ 428c2ecf20Sopenharmony_ci case 21: fn(__VA_ARGS__); fallthrough; \ 438c2ecf20Sopenharmony_ci case 20: fn(__VA_ARGS__); fallthrough; \ 448c2ecf20Sopenharmony_ci case 19: fn(__VA_ARGS__); fallthrough; \ 458c2ecf20Sopenharmony_ci case 18: fn(__VA_ARGS__); fallthrough; \ 468c2ecf20Sopenharmony_ci case 17: fn(__VA_ARGS__); fallthrough; \ 478c2ecf20Sopenharmony_ci case 16: fn(__VA_ARGS__); fallthrough; \ 488c2ecf20Sopenharmony_ci case 15: fn(__VA_ARGS__); fallthrough; \ 498c2ecf20Sopenharmony_ci case 14: fn(__VA_ARGS__); fallthrough; \ 508c2ecf20Sopenharmony_ci case 13: fn(__VA_ARGS__); fallthrough; \ 518c2ecf20Sopenharmony_ci case 12: fn(__VA_ARGS__); fallthrough; \ 528c2ecf20Sopenharmony_ci case 11: fn(__VA_ARGS__); fallthrough; \ 538c2ecf20Sopenharmony_ci case 10: fn(__VA_ARGS__); fallthrough; \ 548c2ecf20Sopenharmony_ci case 9: fn(__VA_ARGS__); fallthrough; \ 558c2ecf20Sopenharmony_ci case 8: fn(__VA_ARGS__); fallthrough; \ 568c2ecf20Sopenharmony_ci case 7: fn(__VA_ARGS__); fallthrough; \ 578c2ecf20Sopenharmony_ci case 6: fn(__VA_ARGS__); fallthrough; \ 588c2ecf20Sopenharmony_ci case 5: fn(__VA_ARGS__); fallthrough; \ 598c2ecf20Sopenharmony_ci case 4: fn(__VA_ARGS__); fallthrough; \ 608c2ecf20Sopenharmony_ci case 3: fn(__VA_ARGS__); fallthrough; \ 618c2ecf20Sopenharmony_ci case 2: fn(__VA_ARGS__); fallthrough; \ 628c2ecf20Sopenharmony_ci case 1: fn(__VA_ARGS__); fallthrough; \ 638c2ecf20Sopenharmony_ci case 0: break; \ 648c2ecf20Sopenharmony_ci \ 658c2ecf20Sopenharmony_ci default: \ 668c2ecf20Sopenharmony_ci /* \ 678c2ecf20Sopenharmony_ci * Either the iteration count is unreasonable \ 688c2ecf20Sopenharmony_ci * or we need to add more cases above. \ 698c2ecf20Sopenharmony_ci */ \ 708c2ecf20Sopenharmony_ci bad_unroll(); \ 718c2ecf20Sopenharmony_ci break; \ 728c2ecf20Sopenharmony_ci } \ 738c2ecf20Sopenharmony_ci} while (0) 748c2ecf20Sopenharmony_ci 758c2ecf20Sopenharmony_ci#endif /* __ASM_UNROLL_H__ */ 76