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Diffstat (limited to 'arch/xtensa/lib/memset.S')
| -rw-r--r-- | arch/xtensa/lib/memset.S | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/arch/xtensa/lib/memset.S b/arch/xtensa/lib/memset.S new file mode 100644 index 0000000..4de2513 --- /dev/null +++ b/arch/xtensa/lib/memset.S @@ -0,0 +1,160 @@ +/* + * arch/xtensa/lib/memset.S + * + * ANSI C standard library function memset + * (Well, almost. .fixup code might return zero.) + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file "COPYING" in the main directory of + * this archive for more details. + * + * Copyright (C) 2002 Tensilica Inc. + */ + +#include <xtensa/coreasm.h> + +/* + * void *memset(void *dst, int c, size_t length) + * + * The algorithm is as follows: + * Create a word with c in all byte positions + * If the destination is aligned, + * do 16B chucks with a loop, and then finish up with + * 8B, 4B, 2B, and 1B stores conditional on the length. + * If destination is unaligned, align it by conditionally + * setting 1B and 2B and then go to aligned case. + * This code tries to use fall-through branches for the common + * case of an aligned destination (except for the branches to + * the alignment labels). + */ + +/* Load or store instructions that may cause exceptions use the EX macro. */ + +#define EX(insn,reg1,reg2,offset,handler) \ +9: insn reg1, reg2, offset; \ + .section __ex_table, "a"; \ + .word 9b, handler; \ + .previous + + +.text +.align 4 +.global memset +.type memset,@function +memset: + entry sp, 16 # minimal stack frame + # a2/ dst, a3/ c, a4/ length + extui a3, a3, 0, 8 # mask to just 8 bits + slli a7, a3, 8 # duplicate character in all bytes of word + or a3, a3, a7 # ... + slli a7, a3, 16 # ... + or a3, a3, a7 # ... + mov a5, a2 # copy dst so that a2 is return value + movi a6, 3 # for alignment tests + bany a2, a6, .Ldstunaligned # if dst is unaligned +.L0: # return here from .Ldstunaligned when dst is aligned + srli a7, a4, 4 # number of loop iterations with 16B + # per iteration + bnez a4, .Laligned + retw + +/* + * Destination is word-aligned. + */ + # set 16 bytes per iteration for word-aligned dst + .align 4 # 1 mod 4 alignment for LOOPNEZ + .byte 0 # (0 mod 4 alignment for LBEG) +.Laligned: +#if XCHAL_HAVE_LOOPS + loopnez a7, .Loop1done +#else /* !XCHAL_HAVE_LOOPS */ + beqz a7, .Loop1done + slli a6, a7, 4 + add a6, a6, a5 # a6 = end of last 16B chunk +#endif /* !XCHAL_HAVE_LOOPS */ +.Loop1: + EX(s32i, a3, a5, 0, memset_fixup) + EX(s32i, a3, a5, 4, memset_fixup) + EX(s32i, a3, a5, 8, memset_fixup) + EX(s32i, a3, a5, 12, memset_fixup) + addi a5, a5, 16 +#if !XCHAL_HAVE_LOOPS + blt a5, a6, .Loop1 +#endif /* !XCHAL_HAVE_LOOPS */ +.Loop1done: + bbci.l a4, 3, .L2 + # set 8 bytes + EX(s32i, a3, a5, 0, memset_fixup) + EX(s32i, a3, a5, 4, memset_fixup) + addi a5, a5, 8 +.L2: + bbci.l a4, 2, .L3 + # set 4 bytes + EX(s32i, a3, a5, 0, memset_fixup) + addi a5, a5, 4 +.L3: + bbci.l a4, 1, .L4 + # set 2 bytes + EX(s16i, a3, a5, 0, memset_fixup) + addi a5, a5, 2 +.L4: + bbci.l a4, 0, .L5 + # set 1 byte + EX(s8i, a3, a5, 0, memset_fixup) +.L5: +.Lret1: + retw + +/* + * Destination is unaligned + */ + +.Ldstunaligned: + bltui a4, 8, .Lbyteset # do short copies byte by byte + bbci.l a5, 0, .L20 # branch if dst alignment half-aligned + # dst is only byte aligned + # set 1 byte + EX(s8i, a3, a5, 0, memset_fixup) + addi a5, a5, 1 + addi a4, a4, -1 + # now retest if dst aligned + bbci.l a5, 1, .L0 # if now aligned, return to main algorithm +.L20: + # dst half-aligned + # set 2 bytes + EX(s16i, a3, a5, 0, memset_fixup) + addi a5, a5, 2 + addi a4, a4, -2 + j .L0 # dst is now aligned, return to main algorithm + +/* + * Byte by byte set + */ + .align 4 + .byte 0 # 1 mod 4 alignment for LOOPNEZ + # (0 mod 4 alignment for LBEG) +.Lbyteset: +#if XCHAL_HAVE_LOOPS + loopnez a4, .Lbytesetdone +#else /* !XCHAL_HAVE_LOOPS */ + beqz a4, .Lbytesetdone + add a6, a5, a4 # a6 = ending address +#endif /* !XCHAL_HAVE_LOOPS */ +.Lbyteloop: + EX(s8i, a3, a5, 0, memset_fixup) + addi a5, a5, 1 +#if !XCHAL_HAVE_LOOPS + blt a5, a6, .Lbyteloop +#endif /* !XCHAL_HAVE_LOOPS */ +.Lbytesetdone: + retw + + + .section .fixup, "ax" + .align 4 + +/* We return zero if a failure occurred. */ + +memset_fixup: + movi a2, 0 + retw |
