/* * 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