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1 %//////////////////////////////////////////////////////////////////////////////
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2 %
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3 % Copyright (c) 2007,2009 Daniel Adler <dadler@uni-goettingen.de>,
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4 % Tassilo Philipp <tphilipp@potion-studios.com>
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5 %
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6 % Permission to use, copy, modify, and distribute this software for any
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7 % purpose with or without fee is hereby granted, provided that the above
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8 % copyright notice and this permission notice appear in all copies.
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9 %
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10 % THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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11 % WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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12 % MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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13 % ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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14 % WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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15 % ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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16 % OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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17 %
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18 %//////////////////////////////////////////////////////////////////////////////
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19
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20 % ==================================================
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21 % PowerPC 32
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22 % ==================================================
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23 \subsection{PowerPC (32bit) Calling Convention}
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24
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25 \paragraph{Overview}
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26
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27 \begin{itemize}
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28 \item Word size is 32 bits
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29 \item Big endian (MSB) and litte endian (LSB) operating modes.
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30 \item Processor operates on floats in double precision floating point arithmetc (IEEE-754) values directly (single precision is converted on the fly)
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31 \item Apple Mac OS X/Darwin PPC is specified in "Mac OS X ABI Function Call Guide"\cite{ppcMacOSX}. It uses Big Endian (MSB).
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32 \item Linux PPC 32-bit ABI is specified in "LSB for PPC"\cite{ppc32LSB} which is based on "System V ABI". It uses Big Endian (MSB).
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33 \item PowerPC EABI is defined in the "PowerPC Embedded Application Binary Interface 32-Bit Implementation".
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34 \end{itemize}
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35
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36
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37 \paragraph{\product{dyncall} support}
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38
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39 \product{Dyncall} and \product{dyncallback} are supported for PowerPC (32bit) Big Endian (MSB) on Darwin (tested on Apple Mac OS X) and Linux, however, fail for *BSD.
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40
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41
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42 \subsubsection{Mac OS X/Darwin}
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43
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44 \paragraph{Registers and register usage}
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45
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46 \begin{table}[h]
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47 \begin{tabular}{3 B}
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48 \hline
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49 Name & Brief description\\
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50 \hline
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51 {\bf gpr0} & scratch\\
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52 {\bf gpr1} & stack pointer\\
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53 {\bf gpr2} & scratch\\
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54 {\bf gpr3} & return value, parameter 0 if integer or pointer\\
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55 {\bf gpr4-gpr10} & return value, parameter 1-7 for integer or pointer parameters\\
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56 {\bf gpr11} & permanent\\
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57 {\bf gpr12} & branch target for dynamic code generation\\
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58 {\bf gpr13-31} & permanent\\
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59 {\bf fpr0} & scratch\\
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60 {\bf fpr1-fpr13} & parameter 0-12 for floating point (always double precision)\\
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61 {\bf fpr14-fpr31} & permanent\\
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62 {\bf v0-v1} & scratch\\
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63 {\bf v2-v13} & vector parameters\\
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64 {\bf v14-v19} & scratch\\
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65 {\bf v20-v31} & permanent\\
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66 {\bf lr} & scratch, link-register\\
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67 {\bf ctr} & scratch, count-register\\
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68 {\bf cr0-cr1} & scratch\\
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69 {\bf cr2-cr4} & permanent\\
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70 {\bf cr5-cr7} & scratch\\
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71 \hline
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72 \end{tabular}
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73 \caption{Register usage on Darwin PowerPC 32-Bit}
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74 \end{table}
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75
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76 \paragraph{Parameter passing}
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77
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78 \begin{itemize}
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79 \item stack parameter order: right-to-left@@@?
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80 \item caller cleans up the stack@@@?
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81 \item the first 8 integer parameters are passed in registers gpr3-gpr10
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82 \item the first 12 floating point parameters are passed in registers fpr1-fpr13
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83 \item if a float parameter is passed via a register, gpr registers are skipped for subsequent integer parameters (based on the size of
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84 the float - 1 register for single precision and 2 for double precision floating point values)
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85 \item the caller pushes subsequent parameters onto the stack
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86 \item for every parameter passed via a register, space is reserved in the stack parameter area (in order to spill the parameters if
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87 needed - e.g. varargs)
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88 \item ellipsis calls take floating point values in int and float registers (single precision floats are promoted to double precision
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89 as defined for ellipsis calls)
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90 \item all nonvector parameters are aligned on 4-byte boundaries
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91 \item vector parameters are aligned on 16-byte boundaries
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92 \item integer parameters \textless\ 32 bit occupy high-order bytes of their 4-byte area
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93 \item composite parameters with size of 1 or 2 bytes occupy low-order bytes of their 4-byte area. INCONSISTENT with other 32-bit PPC
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94 binary interfaces. In AIX and OS 9, padding bytes always follow the data structure
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95 \item composite parameters 3 bytes or larger in size occupy high-order bytes
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96 \end{itemize}
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97
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98
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99 \paragraph{Return values}
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100
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101 \begin{itemize}
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102 \item return values of integer \textless=\ 32bit or pointer type use gpr3
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103 \item 64 bit integers use gpr3 and gpr4 (hiword in gpr3, loword in gpr4)
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104 \item floating point values are returned via fpr1
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105 \item structures \textless=\ 64 bits use gpr3 and gpr4
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106 \item for types \textgreater\ 64 bits, a secret first parameter with an address to the return value is passed
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107 \end{itemize}
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108
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109 \pagebreak
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110
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111 \paragraph{Stack layout}
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112
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113 Stack frame is always 16-byte aligned. Stack directly after function prolog:\\
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114
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115 \begin{figure}[h]
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116 \begin{tabular}{5|3|1 1}
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117 \hhline{~-~~}
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118 & \vdots & & \\
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119 \hhline{~=~~}
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120 local data & & & \mrrbrace{13}{caller's frame} \\
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121 \hhline{~-~~}
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122 \mrlbrace{6}{parameter area} & \ldots & \mrrbrace{3}{stack parameters} & \\
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123 & \ldots & & \\
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124 & \ldots & & \\
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125 & \ldots & \mrrbrace{3}{spill area (as needed)} & \\
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126 & \ldots & & \\
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127 & gpr3 or fpr1 & & \\
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128 \hhline{~-~~}
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129 \mrlbrace{6}{linkage area} & reserved & & \\
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130 & reserved & & \\
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131 & reserved & & \\
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132 & return address & & \\
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133 & reserved for callee & & \\
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134 & saved by callee & & \\
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135 \hhline{~=~~}
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136 local data & & & \mrrbrace{3}{current frame} \\
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137 \hhline{~-~~}
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138 parameter area & & & \\
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139 \hhline{~-~~}
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140 linkage area & \vdots & & \\
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141 \hhline{~-~~}
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142 \end{tabular}
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143 \caption{Stack layout on ppc32 Darwin}
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144 \end{figure}
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145
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146 \subsubsection{System V PPC 32-bit}
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147
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148 \paragraph{Status}
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149
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150 \begin{itemize}
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151 \item C++ this calls do not work.
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152 \item Callbacks don't work on *BSD.
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153 \end{itemize}
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154
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155 \paragraph{Registers and register usage}
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156
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157 \begin{table}[h]
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158 \begin{tabular}{3 B}
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159 \hline
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160 Name & Brief description\\
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161 \hline
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162 {\bf r0} & scratch\\
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163 {\bf r1} & stack pointer\\
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164 {\bf r2} & system-reserved\\
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165 {\bf r3-r4} & parameter passing and return value\\
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166 {\bf r5-r10} & parameter passing\\
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167 {\bf r11-r12} & scratch\\
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168 {\bf r13} & Small data area pointer register\\
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169 {\bf r14-r30} & Local variables\\
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170 {\bf r31} & Used for local variables or \emph{environment pointer}\\
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171 {\bf f0} & scratch\\
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172 {\bf f1} & parameter passing and return value\\
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173 {\bf f2-f8} & parameter passing\\
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174 {\bf f9-13} & scratch\\
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175 {\bf f14-f31} & Local variables\\
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176 {\bf cr0-cr7} & Conditional register fields, each 4-bit wide (cr0-cr1 and cr5-cr7 are scratch)\\
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177 {\bf lr} & Link register (scratch)\\
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178 {\bf ctr} & Count register (scratch) \\
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179 {\bf xer} & Fixed-point exception register (scratch)\\
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180 {\bf fpscr} & Floating-point Status and Control Register\\
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181
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182 % {\bf v0-v1} & scratch\\
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183 % {\bf v2-v13} & vector parameters\\
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184 % {\bf v14-v19} & scratch\\
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185 % {\bf v20-v31} & permanent\\
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186 % {\bf lr} & scratch, link-register\\
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187 % {\bf ctr} & scratch, count-register\\
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188 % {\bf cr0-cr1} & scratch\\
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189 % {\bf cr2-cr4} & permanent\\
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190 % {\bf cr5-cr7} & scratch\\
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191 \hline
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192 \end{tabular}
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193 \caption{Register usage on System V ABI PowerPC Processor}
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194 \end{table}
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195
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196 \paragraph{Parameter passing}
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197
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198 \begin{itemize}
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199 \item Stack pointer (r1) is always 16-byte aligned. The EABI differs here - it is 8-byte alignment.
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200 \item 8 general-purpose registers (r3-r10) for integer and pointer types.
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201 \item 8 floating-pointer registers (f1-f8) for float (promoted to double) and double types.
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202 \item Additional arguments are passed on the stack directly after the back-chain and saved return address (8 bytes structure) on the callers stack frame.
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203 \item 64-bit integer data types are passed in general-purpose registers as a whole in two
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204 32-bit general purpose registers (an odd and an even e.g. r3 and r4), probably skipping an even integer register.
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205 or passed on the stack. They are never splitted into a register and stack part.
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206 \item Ellipse calls set CR bit 6
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207
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208 \end{itemize}
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209
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210 \paragraph{Return values}
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211
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212 \begin{itemize}
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213 \item 32-bit integers use register r3, 64-bit use registers r3 and r4 (hiword in r3, loword in r4).
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214 \item floating-point values are returned using register f1.
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215 \end{itemize}
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216
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217 \pagebreak
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218
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219 \paragraph{Stack layout}
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220
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221 Stack frame is always 16-byte aligned. Stack directly after function prolog:\\
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222
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223 \begin{figure}[h]
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224 \begin{tabular}{5|3|1 1}
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225 \hhline{~-~~}
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226 & \vdots & & \\
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227 \hhline{~=~~}
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228 local data & & & \mrrbrace{6}{caller's frame} \\
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229 \hhline{~-~~}
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230 \mrlbrace{3}{parameter area} & \ldots & \mrrbrace{3}{stack parameters} & \\
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231 & \ldots & & \\
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232 & \ldots & & \\
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233 \hhline{~-~~}
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234 & saved return address (for callee) & & \\
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235 \hhline{~-~~}
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236 & parent stack frame pointer & & \\
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237 \hhline{~=~~}
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238 local data & & & \mrrbrace{3}{current frame} \\
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239 \hhline{~-~~}
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240 parameter area & & & \\
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241 \hhline{~-~~}
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242 & \vdots & & \\
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243 \hhline{~-~~}
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244 \end{tabular}
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245 \\
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246 \\
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247 \\
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248 \caption{Stack layout on System V ABI for PowerPC 32-bit calling convention}
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249 \end{figure}
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