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0
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1 module dmd.ReturnStatement;
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2
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3 import dmd.Loc;
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4 import dmd.Statement;
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5 import dmd.GotoStatement;
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6 import dmd.STC;
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7 import dmd.CompoundStatement;
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8 import dmd.Id;
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9 import dmd.AssignExp;
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10 import dmd.ExpStatement;
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11 import dmd.FuncDeclaration;
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12 import dmd.IntegerExp;
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13 import dmd.ThisExp;
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14 import dmd.StructDeclaration;
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15 import dmd.TypeFunction;
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16 import dmd.CSX;
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17 import dmd.RET;
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18 import dmd.TOK;
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19 import dmd.Type;
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20 import dmd.Expression;
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21 import dmd.StructLiteralExp;
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22 import dmd.TypeStruct;
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23 import dmd.Scope;
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24 import dmd.OutBuffer;
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25 import dmd.HdrGenState;
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26 import dmd.InterState;
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27 import dmd.InlineCostState;
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28 import dmd.InlineDoState;
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29 import dmd.InlineScanState;
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30 import dmd.IRState;
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31 import dmd.TY;
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32 import dmd.WANT;
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33 import dmd.VarExp;
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34 import dmd.VarDeclaration;
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35 import dmd.BE;
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36 import dmd.codegen.Util;
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37
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38 import dmd.backend.Blockx;
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39 import dmd.backend.elem;
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40 import dmd.backend.TYM;
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41 import dmd.backend.Util;
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42 import dmd.backend.OPER;
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43 import dmd.backend.mTY;
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44 import dmd.backend.BC;
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45
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46 class ReturnStatement : Statement
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47 {
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48 Expression exp;
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49
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50 this(Loc loc, Expression exp)
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51 {
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52 super(loc);
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53 this.exp = exp;
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54 }
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55
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56 Statement syntaxCopy()
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57 {
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58 Expression e = exp ? exp.syntaxCopy() : null;
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59 return new ReturnStatement(loc, e);
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60 }
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61
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62 void toCBuffer(OutBuffer buf, HdrGenState* hgs)
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63 {
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64 assert(false);
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65 }
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66
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67 Statement semantic(Scope sc)
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68 {
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69 //printf("ReturnStatement.semantic() %s\n", toChars());
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70
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71 FuncDeclaration fd = sc.parent.isFuncDeclaration();
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72 Scope scx = sc;
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73 int implicit0 = 0;
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74
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75 if (sc.fes)
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76 {
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77 // Find scope of function foreach is in
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78 for (; 1; scx = scx.enclosing)
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79 {
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80 assert(scx);
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81 if (scx.func !is fd)
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82 {
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83 fd = scx.func; // fd is now function enclosing foreach
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84 break;
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85 }
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86 }
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87 }
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88
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89 Type tret = fd.type.nextOf();
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90 if (fd.tintro) {
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91 /* We'll be implicitly casting the return expression to tintro
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92 */
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93 tret = fd.tintro.nextOf();
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94 }
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95
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96 Type tbret = null;
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97
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98 if (tret) {
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99 tbret = tret.toBasetype();
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100 }
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101
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102 // main() returns 0, even if it returns void
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103 if (!exp && (!tbret || tbret.ty == TY.Tvoid) && fd.isMain())
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104 {
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105 implicit0 = 1;
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106 exp = new IntegerExp(0);
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107 }
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108
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109 if (sc.incontract || scx.incontract)
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110 error("return statements cannot be in contracts");
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111
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112 if (sc.tf || scx.tf)
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113 error("return statements cannot be in finally, scope(exit) or scope(success) bodies");
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114
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115 if (fd.isCtorDeclaration())
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116 {
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117 // Constructors implicitly do:
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118 // return this;
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119 if (exp && exp.op != TOK.TOKthis) {
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120 error("cannot return expression from constructor");
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121 }
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122
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123 exp = new ThisExp(Loc(0));
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124 }
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125
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126 if (!exp) {
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127 fd.nrvo_can = 0;
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128 }
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129
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130 if (exp)
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131 {
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132 fd.hasReturnExp |= 1;
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133
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134 exp = exp.semantic(sc);
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135 exp = resolveProperties(sc, exp);
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136 exp = exp.optimize(WANT.WANTvalue);
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137
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138 if (fd.nrvo_can && exp.op == TOK.TOKvar) {
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139 VarExp ve = cast(VarExp)exp;
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140 VarDeclaration v = ve.var.isVarDeclaration();
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141
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142 if ((cast(TypeFunction)fd.type).isref) {
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143 // Function returns a reference
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144 fd.nrvo_can = 0;
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145 } else if (!v || v.isOut() || v.isRef()) {
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146 fd.nrvo_can = 0;
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147 } else if (tbret.ty == TY.Tstruct && (cast(TypeStruct)tbret).sym.dtor) {
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148 // Struct being returned has destructors
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149 fd.nrvo_can = 0;
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150 } else if (fd.nrvo_var is null) {
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151 if (!v.isDataseg() && !v.isParameter() && v.toParent2() == fd) {
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152 //printf("Setting nrvo to %s\n", v.toChars());
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153 fd.nrvo_var = v;
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154 } else {
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155 fd.nrvo_can = 0;
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156 }
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157 } else if (fd.nrvo_var != v) {
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158 fd.nrvo_can = 0;
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159 }
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160 } else {
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161 fd.nrvo_can = 0;
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162 }
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163
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164 if (fd.returnLabel && tbret.ty != TY.Tvoid) {
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165 ;
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166 } else if (fd.inferRetType) {
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167 if (fd.type.nextOf()) {
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168 if (!exp.type.equals(fd.type.nextOf()))
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169 error("mismatched function return type inference of %s and %s", exp.type.toChars(), fd.type.nextOf().toChars());
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170 }
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171 else
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172 {
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173 (cast(TypeFunction)fd.type).next = exp.type;
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174 fd.type = fd.type.semantic(loc, sc);
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175 if (!fd.tintro)
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176 {
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177 tret = fd.type.nextOf();
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178 tbret = tret.toBasetype();
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179 }
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180 }
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181 } else if (tbret.ty != TY.Tvoid)
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182 {
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183 exp = exp.implicitCastTo(sc, tret);
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184 exp = exp.optimize(WANT.WANTvalue);
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185 }
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186 } else if (fd.inferRetType) {
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187 if (fd.type.nextOf())
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188 {
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189 if (fd.type.nextOf().ty != TY.Tvoid) {
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190 error("mismatched function return type inference of void and %s", fd.type.nextOf().toChars());
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191 }
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192 }
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193 else
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194 {
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195 (cast(TypeFunction*)fd.type).next = Type.tvoid;
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196 fd.type = fd.type.semantic(loc, sc);
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197 if (!fd.tintro)
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198 {
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199 tret = Type.tvoid;
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200 tbret = tret;
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201 }
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202 }
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203 }
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204 else if (tbret.ty != TY.Tvoid) {// if non-void return
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205 error("return expression expected");
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206 }
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207
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208 if (sc.fes)
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209 {
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210 Statement s;
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211
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212 if (exp && !implicit0)
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213 {
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214 exp = exp.implicitCastTo(sc, tret);
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215 }
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216 if (!exp || exp.op == TOK.TOKint64 || exp.op == TOK.TOKfloat64 ||
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217 exp.op == TOK.TOKimaginary80 || exp.op == TOK.TOKcomplex80 ||
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218 exp.op == TOK.TOKthis || exp.op == TOK.TOKsuper || exp.op == TOK.TOKnull ||
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219 exp.op == TOK.TOKstring)
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220 {
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221 sc.fes.cases.push(cast(void*)this);
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222 // Construct: return cases.dim+1;
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223 s = new ReturnStatement(Loc(0), new IntegerExp(sc.fes.cases.dim + 1));
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224 }
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225 else if (fd.type.nextOf().toBasetype() == Type.tvoid)
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226 {
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227 s = new ReturnStatement(Loc(0), null);
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228 sc.fes.cases.push(cast(void*)s);
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229
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230 // Construct: { exp; return cases.dim + 1; }
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231 Statement s1 = new ExpStatement(loc, exp);
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232 Statement s2 = new ReturnStatement(Loc(0), new IntegerExp(sc.fes.cases.dim + 1));
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233 s = new CompoundStatement(loc, s1, s2);
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234 }
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235 else
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236 {
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237 // Construct: return vresult;
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238 if (!fd.vresult)
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239 {
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240 // Declare vresult
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241 VarDeclaration v = new VarDeclaration(loc, tret, Id.result, null);
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242 v.noauto = true;
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243 v.semantic(scx);
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244 if (!scx.insert(v)) {
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245 assert(0);
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246 }
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247 v.parent = fd;
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248 fd.vresult = v;
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249 }
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250
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251 s = new ReturnStatement(Loc(0), new VarExp(Loc(0), fd.vresult));
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252 sc.fes.cases.push(cast(void*)s);
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253
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254 // Construct: { vresult = exp; return cases.dim + 1; }
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255 exp = new AssignExp(loc, new VarExp(Loc(0), fd.vresult), exp);
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256 exp.op = TOK.TOKconstruct;
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257 exp = exp.semantic(sc);
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258 Statement s1 = new ExpStatement(loc, exp);
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259 Statement s2 = new ReturnStatement(Loc(0), new IntegerExp(sc.fes.cases.dim + 1));
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260 s = new CompoundStatement(loc, s1, s2);
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261 }
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262 return s;
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263 }
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264
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265 if (exp)
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266 {
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267 if (fd.returnLabel && tbret.ty != TY.Tvoid)
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268 {
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269 assert(fd.vresult);
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270 VarExp v = new VarExp(Loc(0), fd.vresult);
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271
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272 exp = new AssignExp(loc, v, exp);
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273 exp.op = TOK.TOKconstruct;
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274 exp = exp.semantic(sc);
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275 }
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276
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277 if ((cast(TypeFunction)fd.type).isref && !fd.isCtorDeclaration())
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278 { // Function returns a reference
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279 if (tbret.isMutable())
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280 exp = exp.modifiableLvalue(sc, exp);
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281 else
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282 exp = exp.toLvalue(sc, exp);
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283
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284 if (exp.op == TOK.TOKvar)
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285 {
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286 VarExp ve = cast(VarExp)exp;
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287 VarDeclaration v = ve.var.isVarDeclaration();
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288 if (v && !v.isDataseg() && !(v.storage_class & (STC.STCref | STC.STCout))) {
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289 error("escaping reference to local variable %s", v.toChars());
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290 }
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291 }
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292 }
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293
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294 //exp.dump(0);
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295 //exp.print();
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296 exp.checkEscape();
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297 }
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298
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299 /* BUG: need to issue an error on:
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300 * this
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301 * { if (x) return;
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302 * super();
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303 * }
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304 */
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305
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306 if (sc.callSuper & CSX.CSXany_ctor && !(sc.callSuper & (CSX.CSXthis_ctor | CSX.CSXsuper_ctor))) {
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307 error("return without calling constructor");
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308 }
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309
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310 sc.callSuper |= CSX.CSXreturn;
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311
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312 // See if all returns are instead to be replaced with a goto returnLabel;
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313 if (fd.returnLabel)
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314 {
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315 GotoStatement gs = new GotoStatement(loc, Id.returnLabel);
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316
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317 gs.label = fd.returnLabel;
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318 if (exp)
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319 {
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320 /* Replace: return exp;
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321 * with: exp; goto returnLabel;
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322 */
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323 Statement s = new ExpStatement(Loc(0), exp);
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324 return new CompoundStatement(loc, s, gs);
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325 }
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326 return gs;
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327 }
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328
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329 if (exp && tbret.ty == TY.Tvoid && !fd.isMain())
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330 {
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331 /* Replace:
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332 * return exp;
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333 * with:
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334 * exp; return;
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335 */
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336 Statement s = new ExpStatement(loc, exp);
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337 loc = Loc(0);
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338 exp = null;
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339 return new CompoundStatement(loc, s, this);
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340 }
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341
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342 return this;
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343 }
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344
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345 BE blockExit()
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346 {
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347 BE result = BE.BEreturn;
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348 if (exp && exp.canThrow())
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349 result |= BE.BEthrow;
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350
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351 return result;
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352 }
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353
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354 Expression interpret(InterState* istate)
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355 {
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356 assert(false);
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357 }
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358
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359 int inlineCost(InlineCostState* ics)
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360 {
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361 // Can't handle return statements nested in if's
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362 if (ics.nested)
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363 return COST_MAX;
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364 return exp ? exp.inlineCost(ics) : 0;
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365 }
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366
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367 Expression doInline(InlineDoState ids)
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368 {
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369 //printf("ReturnStatement.doInline() '%s'\n", exp ? exp.toChars() : "");
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370 return exp ? exp.doInline(ids) : null;
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371 }
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372
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373 Statement inlineScan(InlineScanState* iss)
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374 {
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375 //printf("ReturnStatement.inlineScan()\n");
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376 if (exp)
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377 {
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378 exp = exp.inlineScan(iss);
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379 }
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380 return this;
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381 }
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382
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383 void toIR(IRState* irs)
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384 {
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385 Blockx* blx = irs.blx;
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386
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387 incUsage(irs, loc);
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388 if (exp)
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389 {
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390 elem *e;
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391
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392 FuncDeclaration func = irs.getFunc();
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393 assert(func);
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394 assert(func.type.ty == TY.Tfunction);
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395 TypeFunction tf = cast(TypeFunction)(func.type);
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396
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397 RET retmethod = tf.retStyle();
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398 if (retmethod == RET.RETstack)
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399 {
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400 elem* es;
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401
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402 /* If returning struct literal, write result
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403 * directly into return value
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404 */
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405 if (exp.op == TOK.TOKstructliteral)
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406 {
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407 assert(false);
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408 /*
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409 StructLiteralExp se = cast(StructLiteralExp)exp;
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410 char save[(StructLiteralExp).sizeof];
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411 memcpy(save, se, sizeof(StructLiteralExp));
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412 se.sym = irs.shidden;
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413 se.soffset = 0;
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414 se.fillHoles = 1;
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415 e = exp.toElem(irs);
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416 memcpy(se, save, sizeof(StructLiteralExp));
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417 */
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418 }
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419 else
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420 e = exp.toElem(irs);
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421
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422 assert(e);
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423
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424 if (exp.op == TOK.TOKstructliteral || (func.nrvo_can && func.nrvo_var))
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425 {
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426 // Return value via hidden pointer passed as parameter
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427 // Write exp; return shidden;
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428 es = e;
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429 }
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430 else
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431 {
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432 // Return value via hidden pointer passed as parameter
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433 // Write *shidden=exp; return shidden;
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434 int op;
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435 tym_t ety;
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436
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437 ety = e.Ety;
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438 es = el_una(OPER.OPind,ety,el_var(irs.shidden));
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439 op = (tybasic(ety) == TYM.TYstruct) ? OPER.OPstreq : OPER.OPeq;
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440 es = el_bin(op, ety, es, e);
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441 if (op == OPER.OPstreq)
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442 es.Enumbytes = cast(uint)exp.type.size();
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443 version (DMDV2) {
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444 /* Call postBlit() on *shidden
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445 */
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446 Type tb = exp.type.toBasetype();
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447 //if (tb.ty == TY.Tstruct) exp.dump(0);
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448 if ((exp.op == TOK.TOKvar || exp.op == TOK.TOKdotvar || exp.op == TOK.TOKstar) &&
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449 tb.ty == TY.Tstruct)
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450 { StructDeclaration sd = (cast(TypeStruct)tb).sym;
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451 if (sd.postblit)
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452 {
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453 FuncDeclaration fd = sd.postblit;
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454 elem* ec = el_var(irs.shidden);
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455 ec = callfunc(loc, irs, 1, Type.tvoid, ec, tb.pointerTo(), fd, fd.type, null, null);
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456 es = el_bin(OPER.OPcomma, ec.Ety, es, ec);
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457 }
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458
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459 static if (false) {
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460 /* It has been moved, so disable destructor
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461 */
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462 if (exp.op == TOK.TOKvar)
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463 {
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464 VarExp ve = cast(VarExp)exp;
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465 VarDeclaration v = ve.var.isVarDeclaration();
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466 if (v && v.rundtor)
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467 {
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468 elem* er = el_var(v.rundtor.toSymbol());
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469 er = el_bin(OPER.OPeq, TYM.TYint, er, el_long(TYM.TYint, 0));
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470 es = el_bin(OPER.OPcomma, TYM.TYint, es, er);
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471 }
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472 }
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473 }
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474 }
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475 }
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476 }
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477 e = el_var(irs.shidden);
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478 e = el_bin(OPER.OPcomma, e.Ety, es, e);
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479 }
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480 ///version (DMDV2) {
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481 else if (tf.isref)
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482 { // Reference return, so convert to a pointer
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483 Expression ae = exp.addressOf(null);
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484 e = ae.toElem(irs);
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485 }
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486 ///}
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487 else
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488 {
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489 e = exp.toElem(irs);
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490 assert(e);
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491 }
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492
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493 block_appendexp(blx.curblock, e);
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494 block_next(blx, BC.BCretexp, null);
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495 }
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496 else
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497 block_next(blx, BC.BCret, null);
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|
|
498 }
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|
499
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|
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500 ReturnStatement isReturnStatement() { return this; }
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|
|
501 } |
