124 lines
3.6 KiB
ArmAsm
124 lines
3.6 KiB
ArmAsm
/****************************************************************************
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* libs/libc/machine/xtensa/arch_strlen.S
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include "xtensa_asm.h"
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#include <arch/chip/core-isa.h>
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#include <arch/xtensa/xtensa_abi.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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.section .text
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.begin schedule
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.align 4
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.literal_position
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.global strlen
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.type strlen, @function
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strlen:
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ENTRY(16)
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/* a2 = s */
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addi a3, a2, -4 # because we overincrement at the end
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movi a4, MASK0
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movi a5, MASK1
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movi a6, MASK2
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movi a7, MASK3
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bbsi.l a2, 0, .L1mod2
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bbsi.l a2, 1, .L2mod4
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j .Laligned
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.L1mod2: # address is odd
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l8ui a8, a3, 4 # get byte 0
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addi a3, a3, 1 # advance string pointer
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beqz a8, .Lz3 # if byte 0 is zero
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bbci.l a3, 1, .Laligned # if string pointer is now word-aligned
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.L2mod4: # address is 2 mod 4
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addi a3, a3, 2 # advance ptr for aligned access
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l32i a8, a3, 0 # get word with first two bytes of string
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bnone a8, a6, .Lz2 # if byte 2 (of word, not string) is zero
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bany a8, a7, .Laligned # if byte 3 (of word, not string) is nonzero
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/* Byte 3 is zero. */
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addi a3, a3, 3 # point to zero byte
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sub a2, a3, a2 # subtract to get length
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RET(16)
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/* String is word-aligned. */
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.align 4
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#if XCHAL_HAVE_LOOPS
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#if XCHAL_HAVE_DENSITY
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/* (2 mod 4) alignment for loop instruction */
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#else
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/* (1 mod 4) alignment for loop instruction */
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.byte 0
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.byte 0
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#endif
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#endif
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.Laligned:
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#if XCHAL_HAVE_LOOPS
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#if XCHAL_HAVE_DENSITY
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_movi.n a8, 0 # set up for the maximum loop count
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#else
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_movi a8, 0 # set up for the maximum loop count
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#endif
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loop a8, .Lz3 # loop forever (almost anyway)
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#endif
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1: l32i a8, a3, 4 # get next word of string
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addi a3, a3, 4 # advance string pointer
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bnone a8, a4, .Lz0 # if byte 0 is zero
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bnone a8, a5, .Lz1 # if byte 1 is zero
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bnone a8, a6, .Lz2 # if byte 2 is zero
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#if XCHAL_HAVE_LOOPS
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bnone a8, a7, .Lz3 # if byte 3 is zero
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#else
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bany a8, a7, 1b # repeat if byte 3 is non-zero
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#endif
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.Lz3: /* Byte 3 is zero. */
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addi a3, a3, 3 # point to zero byte
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/* Fall through.... */
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.Lz0: /* Byte 0 is zero. */
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sub a2, a3, a2 # subtract to get length
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RET(16)
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.Lz1: /* Byte 1 is zero. */
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addi a3, a3, 1 # point to zero byte
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sub a2, a3, a2 # subtract to get length
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RET(16)
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.Lz2: /* Byte 2 is zero. */
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addi a3, a3, 2 # point to zero byte
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sub a2, a3, a2 # subtract to get length
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RET(16)
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.end schedule
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.size strlen, . - strlen
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