1 /* SPDX-License-Identifier: GPL-2.0 */ 2 3 /* 4 * Copyright (C) 2023 Google LLC. 5 */ 6 7 #ifndef __UNROLL_H 8 #define __UNROLL_H 9 10 #include <linux/args.h> 11 12 #ifdef CONFIG_CC_IS_CLANG 13 #define __pick_unrolled(x, y) _Pragma(#x) 14 #elif CONFIG_GCC_VERSION >= 80000 15 #define __pick_unrolled(x, y) _Pragma(#y) 16 #else 17 #define __pick_unrolled(x, y) /* not supported */ 18 #endif 19 20 /** 21 * unrolled - loop attributes to ask the compiler to unroll it 22 * 23 * Usage: 24 * 25 * #define BATCH 8 26 * 27 * unrolled_count(BATCH) 28 * for (u32 i = 0; i < BATCH; i++) 29 * // loop body without cross-iteration dependencies 30 * 31 * This is only a hint and the compiler is free to disable unrolling if it 32 * thinks the count is suboptimal and may hurt performance and/or hugely 33 * increase object code size. 34 * Not having any cross-iteration dependencies (i.e. when iter x + 1 depends 35 * on what iter x will do with variables) is not a strict requirement, but 36 * provides best performance and object code size. 37 * Available only on Clang and GCC 8.x onwards. 38 */ 39 40 /* Ask the compiler to pick an optimal unroll count, Clang only */ 41 #define unrolled \ 42 __pick_unrolled(clang loop unroll(enable), /* nothing */) 43 44 /* Unroll each @n iterations of the loop */ 45 #define unrolled_count(n) \ 46 __pick_unrolled(clang loop unroll_count(n), GCC unroll n) 47 48 /* Unroll the whole loop */ 49 #define unrolled_full \ 50 __pick_unrolled(clang loop unroll(full), GCC unroll 65534) 51 52 /* Never unroll the loop */ 53 #define unrolled_none \ 54 __pick_unrolled(clang loop unroll(disable), GCC unroll 1) 55 56 #define UNROLL(N, MACRO, args...) CONCATENATE(__UNROLL_, N)(MACRO, args) 57 58 #define __UNROLL_0(MACRO, args...) 59 #define __UNROLL_1(MACRO, args...) __UNROLL_0(MACRO, args) MACRO(0, args) 60 #define __UNROLL_2(MACRO, args...) __UNROLL_1(MACRO, args) MACRO(1, args) 61 #define __UNROLL_3(MACRO, args...) __UNROLL_2(MACRO, args) MACRO(2, args) 62 #define __UNROLL_4(MACRO, args...) __UNROLL_3(MACRO, args) MACRO(3, args) 63 #define __UNROLL_5(MACRO, args...) __UNROLL_4(MACRO, args) MACRO(4, args) 64 #define __UNROLL_6(MACRO, args...) __UNROLL_5(MACRO, args) MACRO(5, args) 65 #define __UNROLL_7(MACRO, args...) __UNROLL_6(MACRO, args) MACRO(6, args) 66 #define __UNROLL_8(MACRO, args...) __UNROLL_7(MACRO, args) MACRO(7, args) 67 #define __UNROLL_9(MACRO, args...) __UNROLL_8(MACRO, args) MACRO(8, args) 68 #define __UNROLL_10(MACRO, args...) __UNROLL_9(MACRO, args) MACRO(9, args) 69 #define __UNROLL_11(MACRO, args...) __UNROLL_10(MACRO, args) MACRO(10, args) 70 #define __UNROLL_12(MACRO, args...) __UNROLL_11(MACRO, args) MACRO(11, args) 71 #define __UNROLL_13(MACRO, args...) __UNROLL_12(MACRO, args) MACRO(12, args) 72 #define __UNROLL_14(MACRO, args...) __UNROLL_13(MACRO, args) MACRO(13, args) 73 #define __UNROLL_15(MACRO, args...) __UNROLL_14(MACRO, args) MACRO(14, args) 74 #define __UNROLL_16(MACRO, args...) __UNROLL_15(MACRO, args) MACRO(15, args) 75 #define __UNROLL_17(MACRO, args...) __UNROLL_16(MACRO, args) MACRO(16, args) 76 #define __UNROLL_18(MACRO, args...) __UNROLL_17(MACRO, args) MACRO(17, args) 77 #define __UNROLL_19(MACRO, args...) __UNROLL_18(MACRO, args) MACRO(18, args) 78 #define __UNROLL_20(MACRO, args...) __UNROLL_19(MACRO, args) MACRO(19, args) 79 80 #endif /* __UNROLL_H */ 81