1 | ; $Id: ASMMemFirstMismatchingU8.asm 98103 2023-01-17 14:15:46Z vboxsync $
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2 | ;; @file
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3 | ; IPRT - ASMMemFirstMismatchingU8().
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4 | ;
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5 |
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6 | ;
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7 | ; Copyright (C) 2006-2023 Oracle and/or its affiliates.
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8 | ;
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9 | ; This file is part of VirtualBox base platform packages, as
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10 | ; available from https://www.virtualbox.org.
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11 | ;
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12 | ; This program is free software; you can redistribute it and/or
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13 | ; modify it under the terms of the GNU General Public License
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14 | ; as published by the Free Software Foundation, in version 3 of the
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15 | ; License.
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16 | ;
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17 | ; This program is distributed in the hope that it will be useful, but
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18 | ; WITHOUT ANY WARRANTY; without even the implied warranty of
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19 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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20 | ; General Public License for more details.
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21 | ;
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22 | ; You should have received a copy of the GNU General Public License
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23 | ; along with this program; if not, see <https://www.gnu.org/licenses>.
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24 | ;
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25 | ; The contents of this file may alternatively be used under the terms
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26 | ; of the Common Development and Distribution License Version 1.0
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27 | ; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
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28 | ; in the VirtualBox distribution, in which case the provisions of the
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29 | ; CDDL are applicable instead of those of the GPL.
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30 | ;
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31 | ; You may elect to license modified versions of this file under the
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32 | ; terms and conditions of either the GPL or the CDDL or both.
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33 | ;
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34 | ; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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35 | ;
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36 |
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37 |
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38 | ;*******************************************************************************
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39 | ;* Header Files *
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40 | ;*******************************************************************************
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41 | %define RT_ASM_WITH_SEH64
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42 | %include "iprt/asmdefs.mac"
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43 |
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44 |
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45 | BEGINCODE
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46 |
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47 | ;;
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48 | ; Variant of ASMMemFirstMismatchingU8 with a fixed @a u8 value.
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49 | ; We repeat the prolog and join the generic function.
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50 | ;
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51 | RT_BEGINPROC ASMMemFirstNonZero
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52 | ;
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53 | ; Prologue.
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54 | ;
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55 | %if ARCH_BITS != 64
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56 | push xBP
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57 | mov xBP, xSP
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58 | push xDI
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59 | %if ARCH_BITS == 16
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60 | push es
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61 | %endif
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62 | %elifdef ASM_CALL64_MSC
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63 | mov r9, rdi ; save rdi in r9
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64 | %endif
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65 | SEH64_END_PROLOGUE
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66 |
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67 | ;
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68 | ; Normalize input; rdi=pv, rcx=cb, rax=0
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69 | ;
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70 | %if ARCH_BITS == 64
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71 | %ifdef ASM_CALL64_MSC
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72 | mov rdi, rcx
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73 | mov rcx, rdx
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74 | jrcxz RT_CONCAT(NAME(ASMMemFirstMismatchingU8),.return_all_same)
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75 | xor eax, eax
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76 | %else
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77 | mov rcx, rsi
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78 | jrcxz RT_CONCAT(NAME(ASMMemFirstMismatchingU8),.return_all_same)
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79 | xor eax, eax
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80 | %endif
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81 |
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82 | %elif ARCH_BITS == 32
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83 | mov ecx, [ebp + 0ch]
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84 | jecxz RT_CONCAT(NAME(ASMMemFirstMismatchingU8),.return_all_same)
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85 | mov edi, [ebp + 08h]
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86 | xor eax, eax
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87 |
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88 | %elif ARCH_BITS == 16
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89 | mov cx, [bp + 08h] ; cb
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90 | jcxz RT_CONCAT(NAME(ASMMemFirstMismatchingU8),.return16_all_same)
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91 | les di, [bp + 04h] ; pv (far)
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92 | xor ax, ax
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93 |
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94 | %else
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95 | %error "Invalid ARCH_BITS value"
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96 | %endif
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97 |
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98 | ;
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99 | ; Join ASMMemFirstMismatchingU8
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100 | ;
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101 | jmp RT_CONCAT(NAME(ASMMemFirstMismatchingU8),.is_all_zero_joining)
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102 | ENDPROC ASMMemFirstNonZero
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103 |
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104 |
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105 | ;;
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106 | ; Inverted memchr.
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107 | ;
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108 | ; @returns Pointer to the byte which doesn't equal u8.
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109 | ; @returns NULL if all equal to u8.
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110 | ;
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111 | ; @param msc:rcx gcc:rdi pv Pointer to the memory block.
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112 | ; @param msc:rdx gcc:rsi cb Number of bytes in the block. This MUST be aligned on 32-bit!
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113 | ; @param msc:r8b gcc:dl u8 The value it's supposed to be filled with.
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114 | ;
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115 | ; @cproto DECLINLINE(void *) ASMMemFirstMismatchingU8(void const *pv, size_t cb, uint8_t u8)
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116 | ;
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117 | RT_BEGINPROC ASMMemFirstMismatchingU8
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118 | ;
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119 | ; Prologue.
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120 | ;
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121 | %if ARCH_BITS != 64
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122 | push xBP
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123 | mov xBP, xSP
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124 | push xDI
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125 | %if ARCH_BITS == 16
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126 | push es
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127 | %endif
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128 | %elifdef ASM_CALL64_MSC
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129 | mov r9, rdi ; save rdi in r9
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130 | %endif
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131 | SEH64_END_PROLOGUE
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132 |
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133 | %if ARCH_BITS != 16
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134 | ;
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135 | ; The 32-bit and 64-bit variant of the code.
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136 | ;
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137 |
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138 | ; Normalize input; rdi=pv, rcx=cb, rax=eight-times-u8
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139 | %if ARCH_BITS == 64
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140 | %ifdef ASM_CALL64_MSC
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141 | mov rdi, rcx
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142 | mov rcx, rdx
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143 | jrcxz .return_all_same
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144 | movzx r8d, r8b
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145 | mov rax, qword 0101010101010101h
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146 | imul rax, r8
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147 | %else
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148 | mov rcx, rsi
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149 | jrcxz .return_all_same
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150 | movzx edx, dl
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151 | mov rax, qword 0101010101010101h
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152 | imul rax, rdx
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153 | %endif
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154 |
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155 | %elif ARCH_BITS == 32
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156 | mov ecx, [ebp + 0ch]
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157 | jecxz .return_all_same
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158 | mov edi, [ebp + 08h]
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159 | movzx eax, byte [ebp + 10h]
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160 | mov ah, al
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161 | movzx edx, ax
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162 | shl eax, 16
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163 | or eax, edx
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164 | %else
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165 | %error "Invalid ARCH_BITS value"
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166 | %endif
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167 |
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168 | .is_all_zero_joining:
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169 | cld
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170 |
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171 | ; Unaligned pointer? Align it (elsewhere).
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172 | test edi, xCB - 1
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173 | jnz .unaligned_pv
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174 | .aligned_pv:
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175 |
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176 | ; Do the dword/qword scan.
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177 | mov edx, xCB - 1
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178 | and edx, ecx ; Remaining bytes for tail scan
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179 | %if ARCH_BITS == 64
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180 | shr xCX, 3
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181 | repe scasq
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182 | %else
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183 | shr xCX, 2
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184 | repe scasd
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185 | %endif
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186 | jne .multibyte_mismatch
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187 |
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188 | ; Prep for tail scan.
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189 | mov ecx, edx
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190 |
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191 | ;
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192 | ; Byte by byte scan.
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193 | ;
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194 | .byte_by_byte:
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195 | repe scasb
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196 | jne .return_xDI
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197 |
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198 | .return_all_same:
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199 | xor eax, eax
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200 | %ifdef ASM_CALL64_MSC
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201 | mov rdi, r9 ; restore rdi
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202 | %elif ARCH_BITS == 32
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203 | pop edi
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204 | leave
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205 | %endif
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206 | ret
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207 |
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208 | ; Return after byte scan mismatch.
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209 | .return_xDI:
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210 | lea xAX, [xDI - 1]
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211 | %ifdef ASM_CALL64_MSC
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212 | mov rdi, r9 ; restore rdi
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213 | %elif ARCH_BITS == 32
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214 | pop edi
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215 | leave
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216 | %endif
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217 | ret
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218 |
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219 | ;
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220 | ; Multibyte mismatch. We rewind and do a byte scan of the remainder.
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221 | ; (can't just search the qword as the buffer must be considered volatile).
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222 | ;
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223 | .multibyte_mismatch:
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224 | lea xDI, [xDI - xCB]
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225 | lea xCX, [xCX * xCB + xCB]
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226 | or ecx, edx
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227 | jmp .byte_by_byte
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228 |
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229 | ;
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230 | ; Unaligned pointer. If it's worth it, align the pointer, but if the
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231 | ; memory block is too small do the byte scan variant.
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232 | ;
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233 | .unaligned_pv:
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234 | cmp xCX, 4*xCB ; 4 steps seems reasonable.
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235 | jbe .byte_by_byte
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236 |
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237 | ; Unrolled buffer realignment.
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238 | %if ARCH_BITS == 64
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239 | dec xCX
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240 | scasb
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241 | jne .return_xDI
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242 | test edi, xCB - 1
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243 | jz .aligned_pv
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244 |
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245 | dec xCX
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246 | scasb
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247 | jne .return_xDI
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248 | test edi, xCB - 1
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249 | jz .aligned_pv
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250 |
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251 | dec xCX
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252 | scasb
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253 | jne .return_xDI
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254 | test edi, xCB - 1
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255 | jz .aligned_pv
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256 |
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257 | dec xCX
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258 | scasb
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259 | jne .return_xDI
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260 | test edi, xCB - 1
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261 | jz .aligned_pv
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262 | %endif
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263 |
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264 | dec xCX
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265 | scasb
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266 | jne .return_xDI
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267 | test edi, xCB - 1
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268 | jz .aligned_pv
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269 |
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270 | dec xCX
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271 | scasb
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272 | jne .return_xDI
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273 | test edi, xCB - 1
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274 | jz .aligned_pv
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275 |
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276 | dec xCX
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277 | scasb
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278 | jne .return_xDI
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279 | jmp .aligned_pv
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280 |
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281 |
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282 | %else ; ARCH_BITS == 16
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283 |
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284 | ;
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285 | ; The 16-bit variant of the code is a little simpler since we're
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286 | ; working with two byte words in the 'fast' scan. We also keep
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287 | ; this separate from the 32-bit/64-bit code because that allows
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288 | ; avoid a few rex prefixes here and there by using extended
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289 | ; registers (e??) where we don't care about the whole register.
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290 | ;
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291 | CPU 8086
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292 |
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293 | ; Load input parameters.
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294 | mov cx, [bp + 08h] ; cb
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295 | jcxz .return16_all_same
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296 | les di, [bp + 04h] ; pv (far)
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297 | mov al, [bp + 0ah] ; u8
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298 | mov ah, al
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299 |
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300 | .is_all_zero_joining:
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301 | cld
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302 |
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303 | ; Align the pointer.
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304 | test di, 1
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305 | jz .word_scan
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306 |
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307 | dec cx
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308 | scasb
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309 | jne .return16_di
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310 | jcxz .return16_all_same
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311 |
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312 | ; Scan word-by-word.
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313 | .word_scan:
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314 | mov dx, cx
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315 | shr cx, 1
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316 | repe scasw
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317 | jne .word_mismatch
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318 |
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319 | ; do we have a tail byte?
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320 | test dl, 1
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321 | jz .return16_all_same
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322 | scasb
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323 | jne .return16_di
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324 |
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325 | .return16_all_same:
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326 | xor ax, ax
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327 | xor dx, dx
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328 | .return16:
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329 | pop es
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330 | pop di
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331 | pop bp
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332 | ret
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333 |
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334 | .word_mismatch:
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335 | ; back up a word.
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336 | inc cx
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337 | sub di, 2
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338 |
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339 | ; Do byte-by-byte scanning of the rest of the buffer.
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340 | shl cx, 1
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341 | mov dl, 1
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342 | and dl, [bp + 08h] ; cb
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343 | or cl, dl
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344 | repe scasb
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345 | je .return16_all_same
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346 |
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347 | .return16_di:
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348 | mov ax, di
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349 | dec ax
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350 | mov dx, es
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351 | jmp .return16
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352 |
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353 | %endif ; ARCH_BITS == 16
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354 | ENDPROC ASMMemFirstMismatchingU8
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355 |
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