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1 // picoChip ASM file
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2 //
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3 // Support for 16-bit signed division/modulus.
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4 //
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5 // Copyright (C) 2003, 2004, 2005, 2008, 2009 Free Software Foundation, Inc.
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6 // Contributed by picoChip Designs Ltd.
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7 // Maintained by Daniel Towner (daniel.towner@picochip.com)
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8 //
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9 // This file is free software; you can redistribute it and/or modify it
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10 // under the terms of the GNU General Public License as published by the
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11 // Free Software Foundation; either version 3, or (at your option) any
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12 // later version.
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13 //
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14 // This file is distributed in the hope that it will be useful, but
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15 // WITHOUT ANY WARRANTY; without even the implied warranty of
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16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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17 // General Public License for more details.
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18 //
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19 // Under Section 7 of GPL version 3, you are granted additional
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20 // permissions described in the GCC Runtime Library Exception, version
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21 // 3.1, as published by the Free Software Foundation.
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22 //
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23 // You should have received a copy of the GNU General Public License and
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24 // a copy of the GCC Runtime Library Exception along with this program;
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25 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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26 // <http://www.gnu.org/licenses/>.
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27
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28 .section .text
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29
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30 .align 8
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31 .global __divmodhi4
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32 __divmodhi4:
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33 _picoMark_FUNCTION_BEGIN=
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34
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35 // picoChip Function Prologue : &__divmodhi4 = 4 bytes
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36
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37 // 16-bit signed division. Most of the special cases are dealt
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38 // with by the 15-bit signed division library (e.g., division by
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39 // zero, division by 1, and so on). This wrapper simply inverts
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40 // any negative inputs, calls the 15-bit library, and flips any
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41 // results as necessary. The
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42 // only special cases to be handled here are where either the
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43 // divisor or the dividend are the maximum negative values.
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44
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45 // Encode r5 with a bit pattern which indicates whether the
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46 // outputs of the division must be negated. The MSB will be set
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47 // to the sign of the dividend (which controls the remainder's
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48 // sign), while the LSB will store the XOR of the two signs,
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49 // which indicates the quotient's sign. R5 is not modified by the
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50 // 15-bit divmod routine.
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51 sub.0 r1,16#8000#,r15 \ asr.1 r0,15,r4
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52 beq divisorIsLargestNegative \ lsr.0 r1,15,r3
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53 =-> sub.0 r0,16#8000#,r15 \ xor.1 r3,r4,r5
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54
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55 // Handle least negative dividend with a special case. Note that the
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56 // absolute value of the divisor is also computed here.
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57 add.0 [asr r1,15],r1,r3 \ beq dividendIsLargestNegative
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58 =-> xor.0 [asr r1,15],r3,r1 \ stw lr,(fp)-1
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59
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60 // Compute the absolute value of the dividend, and call the main
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61 // divide routine.
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62 add.0 r4,r0,r2 \ jl (&__divmod15) // fn_call &__divmod15
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63 =-> xor.0 r4,r2,r0
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64
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65 handleNegatedResults:
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66 // Speculatively store the negation of the results.
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67 sub.0 0,r0,r2 \ sub.1 0,r1,r3
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68
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69 // Does the quotient need negating? The LSB indicates this.
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70 and.0 r5,1,r15 \ ldw (fp)-1,lr
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71 copyne r2,r0
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72
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73 asr.0 r5,15,r15 \ jr (lr)
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74 =-> copyne r3,r1
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75
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76 dividendIsLargestNegative:
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77
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78 // Divide the constant -32768. Use the Hacker's Delight
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79 // algorithm (i.e., ((dividend / 2) / divisor) * 2) gives
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80 // approximate answer). This code is a special case, so no
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81 // great effort is made to make it fast, only to make it
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82 // small.
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83
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84 lsr.0 r0,1,r0 \ jl (&__divmod15) // fn_call &__divmod15
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85 =-> stw r1,(fp)-2
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86
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87 // Load the original divisor, and compute the new quotient and
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88 // remainder.
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89 lsl.0 r0,1,r0 \ ldw (fp)-2,r3
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90 lsl.0 r1,1,r1 // Fill stall slot
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91
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92 // The error in the quotient is 0 or 1. The error can be determined
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93 // by comparing the remainder to the original divisor. If the
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94 // remainder is bigger, then an error of 1 has been introduced,
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95 // which must be fixed.
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96 sub.0 r1,r3,r15
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97 blo noCompensationForError
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98 =-> nop
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99 add.0 r0,1,r0 \ sub.1 r1,r3,r1
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100 noCompensationForError:
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101 bra handleNegatedResults
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102 =-> nop
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103
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104 divisorIsLargestNegative:
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105 // The flags indicate whether the dividend is also the maximum negative
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106 copy.0 r0,r1 \ copy.1 0,r0
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107 copyeq r0,r1 \ jr (lr)
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108 =-> copyeq 1,r0
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109
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110 _picoMark_FUNCTION_END=
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111 // picoChip Function Epilogue : __divmodhi4
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112
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113
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114 //============================================================================
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115 // All DWARF information between this marker, and the END OF DWARF
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116 // marker should be included in the source file. Search for
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117 // FUNCTION_STACK_SIZE_GOES_HERE and FUNCTION NAME GOES HERE, and
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118 // provide the relevent information. Add markers called
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119 // _picoMark_FUNCTION_BEGIN and _picoMark_FUNCTION_END around the
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120 // function in question.
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121 //============================================================================
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122
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123 //============================================================================
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124 // Frame information.
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125 //============================================================================
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126
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127 .section .debug_frame
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128 _picoMark_DebugFrame=
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129
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130 // Common CIE header.
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131 .unalignedInitLong _picoMark_CieEnd-_picoMark_CieBegin
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132 _picoMark_CieBegin=
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133 .unalignedInitLong 0xffffffff
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134 .initByte 0x1 // CIE Version
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135 .ascii 16#0# // CIE Augmentation
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136 .uleb128 0x1 // CIE Code Alignment Factor
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137 .sleb128 2 // CIE Data Alignment Factor
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138 .initByte 0xc // CIE RA Column
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139 .initByte 0xc // DW_CFA_def_cfa
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140 .uleb128 0xd
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141 .uleb128 0x0
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142 .align 2
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143 _picoMark_CieEnd=
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144
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145 // FDE
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146 _picoMark_LSFDE0I900821033007563=
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147 .unalignedInitLong _picoMark_FdeEnd-_picoMark_FdeBegin
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148 _picoMark_FdeBegin=
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149 .unalignedInitLong _picoMark_DebugFrame // FDE CIE offset
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150 .unalignedInitWord _picoMark_FUNCTION_BEGIN // FDE initial location
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151 .unalignedInitWord _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN
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152 .initByte 0xe // DW_CFA_def_cfa_offset
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153 .uleb128 0x4 // <-- FUNCTION_STACK_SIZE_GOES_HERE
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154 .initByte 0x4 // DW_CFA_advance_loc4
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155 .unalignedInitLong _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN
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156 .initByte 0xe // DW_CFA_def_cfa_offset
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157 .uleb128 0x0
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158 .align 2
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159 _picoMark_FdeEnd=
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160
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161 //============================================================================
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162 // Abbrevation information.
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163 //============================================================================
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164
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165 .section .debug_abbrev
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166 _picoMark_ABBREVIATIONS=
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167
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168 .section .debug_abbrev
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169 .uleb128 0x1 // (abbrev code)
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170 .uleb128 0x11 // (TAG: DW_TAG_compile_unit)
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171 .initByte 0x1 // DW_children_yes
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172 .uleb128 0x10 // (DW_AT_stmt_list)
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173 .uleb128 0x6 // (DW_FORM_data4)
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174 .uleb128 0x12 // (DW_AT_high_pc)
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175 .uleb128 0x1 // (DW_FORM_addr)
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176 .uleb128 0x11 // (DW_AT_low_pc)
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177 .uleb128 0x1 // (DW_FORM_addr)
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178 .uleb128 0x25 // (DW_AT_producer)
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179 .uleb128 0x8 // (DW_FORM_string)
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180 .uleb128 0x13 // (DW_AT_language)
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181 .uleb128 0x5 // (DW_FORM_data2)
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182 .uleb128 0x3 // (DW_AT_name)
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183 .uleb128 0x8 // (DW_FORM_string)
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184 .initByte 0x0
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185 .initByte 0x0
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186
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187 .uleb128 0x2 ;# (abbrev code)
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188 .uleb128 0x2e ;# (TAG: DW_TAG_subprogram)
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189 .initByte 0x0 ;# DW_children_no
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190 .uleb128 0x3 ;# (DW_AT_name)
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191 .uleb128 0x8 ;# (DW_FORM_string)
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192 .uleb128 0x11 ;# (DW_AT_low_pc)
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193 .uleb128 0x1 ;# (DW_FORM_addr)
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194 .uleb128 0x12 ;# (DW_AT_high_pc)
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195 .uleb128 0x1 ;# (DW_FORM_addr)
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196 .initByte 0x0
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197 .initByte 0x0
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198
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199 .initByte 0x0
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200
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201 //============================================================================
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202 // Line information. DwarfLib requires this to be present, but it can
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203 // be empty.
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204 //============================================================================
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205
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206 .section .debug_line
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207 _picoMark_LINES=
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208
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209 //============================================================================
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210 // Debug Information
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211 //============================================================================
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212 .section .debug_info
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213
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214 //Fixed header.
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215 .unalignedInitLong _picoMark_DEBUG_INFO_END-_picoMark_DEBUG_INFO_BEGIN
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216 _picoMark_DEBUG_INFO_BEGIN=
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217 .unalignedInitWord 0x2
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218 .unalignedInitLong _picoMark_ABBREVIATIONS
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219 .initByte 0x2
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220
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221 // Compile unit information.
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222 .uleb128 0x1 // (DIE 0xb) DW_TAG_compile_unit)
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223 .unalignedInitLong _picoMark_LINES
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224 .unalignedInitWord _picoMark_FUNCTION_END
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225 .unalignedInitWord _picoMark_FUNCTION_BEGIN
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226 // Producer is `picoChip'
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227 .ascii 16#70# 16#69# 16#63# 16#6f# 16#43# 16#68# 16#69# 16#70# 16#00#
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228 .unalignedInitWord 0xcafe // ASM language
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229 .ascii 16#0# // Name. DwarfLib expects this to be present.
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230
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231 .uleb128 0x2 ;# (DIE DW_TAG_subprogram)
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232
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233 // FUNCTION NAME GOES HERE. Use `echo name | od -t x1' to get the hex. Each hex
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234 // digit is specified using the format 16#XX#
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235 .ascii 16#5f# 16#64# 16#69# 16#76# 16#6d# 16#6f# 16#64# 16#68# 16#69# 16#34# 16#0# // Function name `_divmodhi4'
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236 .unalignedInitWord _picoMark_FUNCTION_BEGIN // DW_AT_low_pc
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237 .unalignedInitWord _picoMark_FUNCTION_END // DW_AT_high_pc
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238
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239 .initByte 0x0 // end of compile unit children.
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240
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241 _picoMark_DEBUG_INFO_END=
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242
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243 //============================================================================
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244 // END OF DWARF
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245 //============================================================================
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246 .section .endFile
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