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| /*
| * 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 <linux/linkage.h>
| #include <variant/core.h>
| #include <asm/asmmacro.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).
| */
|
| .text
| ENTRY(__memset)
| WEAK(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(10f) s32i a3, a5, 0
| EX(10f) s32i a3, a5, 4
| EX(10f) s32i a3, a5, 8
| EX(10f) s32i a3, a5, 12
| 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(10f) s32i a3, a5, 0
| EX(10f) s32i a3, a5, 4
| addi a5, a5, 8
| .L2:
| bbci.l a4, 2, .L3
| # set 4 bytes
| EX(10f) s32i a3, a5, 0
| addi a5, a5, 4
| .L3:
| bbci.l a4, 1, .L4
| # set 2 bytes
| EX(10f) s16i a3, a5, 0
| addi a5, a5, 2
| .L4:
| bbci.l a4, 0, .L5
| # set 1 byte
| EX(10f) s8i a3, a5, 0
| .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(10f) s8i a3, a5, 0
| 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(10f) s16i a3, a5, 0
| 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(10f) s8i a3, a5, 0
| addi a5, a5, 1
| #if !XCHAL_HAVE_LOOPS
| blt a5, a6, .Lbyteloop
| #endif /* !XCHAL_HAVE_LOOPS */
| .Lbytesetdone:
| retw
|
| ENDPROC(__memset)
|
| .section .fixup, "ax"
| .align 4
|
| /* We return zero if a failure occurred. */
|
| 10:
| movi a2, 0
| retw
|
|
