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1 module dmd.IfStatement;
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2
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114
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3 import dmd.common;
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4 import dmd.Statement;
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5 import dmd.Argument;
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6 import dmd.Loc;
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7 import dmd.Expression;
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8 import dmd.VarDeclaration;
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9 import dmd.Scope;
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10 import dmd.InterState;
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11 import dmd.OutBuffer;
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12 import dmd.HdrGenState;
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13 import dmd.InlineCostState;
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14 import dmd.InlineDoState;
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15 import dmd.InlineScanState;
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16 import dmd.IRState;
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17 import dmd.BE;
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18 import dmd.WANT;
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19 import dmd.ScopeDsymbol;
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20 import dmd.Type;
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21 import dmd.CondExp;
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22 import dmd.AndAndExp;
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23 import dmd.OrOrExp;
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24 import dmd.AssignExp;
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25 import dmd.VarExp;
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26
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27 import dmd.backend.elem;
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28 import dmd.backend.Util;
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29 import dmd.backend.block;
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30 import dmd.backend.Blockx;
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31 import dmd.backend.BC;
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32
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33 class IfStatement : Statement
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34 {
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35 Argument arg;
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36 Expression condition;
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37 Statement ifbody;
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38 Statement elsebody;
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39
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40 VarDeclaration match; // for MatchExpression results
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41
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42 this(Loc loc, Argument arg, Expression condition, Statement ifbody, Statement elsebody)
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43 {
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44 super(loc);
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45 this.arg = arg;
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46 this.condition = condition;
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47 this.ifbody = ifbody;
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48 this.elsebody = elsebody;
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49 }
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50
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72
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51 override Statement syntaxCopy()
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52 {
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51
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53 Statement i = null;
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54 if (ifbody)
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55 i = ifbody.syntaxCopy();
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56
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57 Statement e = null;
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58 if (elsebody)
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59 e = elsebody.syntaxCopy();
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60
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61 Argument a = arg ? arg.syntaxCopy() : null;
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62 IfStatement s = new IfStatement(loc, a, condition.syntaxCopy(), i, e);
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63 return s;
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64 }
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65
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66 override Statement semantic(Scope sc)
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67 {
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68 condition = condition.semantic(sc);
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69 condition = resolveProperties(sc, condition);
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70 condition = condition.checkToBoolean();
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71
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72 // If we can short-circuit evaluate the if statement, don't do the
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73 // semantic analysis of the skipped code.
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74 // This feature allows a limited form of conditional compilation.
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75 condition = condition.optimize(WANT.WANTflags);
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76
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77 // Evaluate at runtime
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78 uint cs0 = sc.callSuper;
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79 uint cs1;
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80
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81 Scope scd;
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82 if (arg)
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83 {
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84 /* Declare arg, which we will set to be the
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85 * result of condition.
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86 */
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87 ScopeDsymbol sym = new ScopeDsymbol();
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88 sym.parent = sc.scopesym;
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89 scd = sc.push(sym);
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90
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91 Type t = arg.type ? arg.type : condition.type;
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92 match = new VarDeclaration(loc, t, arg.ident, null);
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93 match.noauto = true;
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94 match.semantic(scd);
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95 if (!scd.insert(match))
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96 assert(0);
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97
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98 match.parent = sc.func;
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99
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100 /* Generate:
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101 * (arg = condition)
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102 */
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103 VarExp v = new VarExp(Loc(0), match);
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104 condition = new AssignExp(loc, v, condition);
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105 condition = condition.semantic(scd);
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106 }
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107 else
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108 scd = sc.push();
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109
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110 ifbody = ifbody.semantic(scd);
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111 scd.pop();
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112
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113 cs1 = sc.callSuper;
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114 sc.callSuper = cs0;
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115 if (elsebody)
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116 elsebody = elsebody.semanticScope(sc, null, null);
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117
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118 sc.mergeCallSuper(loc, cs1);
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119
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120 return this;
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121 }
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122
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123 override Expression interpret(InterState istate)
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124 {
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125 assert(false);
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126 }
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127
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72
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128 override void toCBuffer(OutBuffer buf, HdrGenState* hgs)
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129 {
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130 assert(false);
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131 }
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132
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133 override bool usesEH()
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134 {
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135 assert(false);
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136 }
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137
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138 override BE blockExit()
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139 {
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140 //printf("IfStatement::blockExit(%p)\n", this);
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141
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142 BE result = BE.BEnone;
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143 if (condition.canThrow())
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144 result |= BE.BEthrow;
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145 if (condition.isBool(true))
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146 {
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147 if (ifbody)
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148 result |= ifbody.blockExit();
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149 else
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150 result |= BE.BEfallthru;
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151 }
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152 else if (condition.isBool(false))
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153 {
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154 if (elsebody)
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155 result |= elsebody.blockExit();
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156 else
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157 result |= BE.BEfallthru;
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158 }
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159 else
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160 {
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161 if (ifbody)
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162 result |= ifbody.blockExit();
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163 else
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164 result |= BE.BEfallthru;
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165
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166 if (elsebody)
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167 result |= elsebody.blockExit();
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168 else
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169 result |= BE.BEfallthru;
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170 }
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171
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172 //printf("IfStatement::blockExit(%p) = x%x\n", this, result);
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173 return result;
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174 }
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175
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176 override IfStatement isIfStatement() { return this; }
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177
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178 override int inlineCost(InlineCostState* ics)
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179 {
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180 int cost;
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181
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182 /* Can't declare variables inside ?: expressions, so
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183 * we cannot inline if a variable is declared.
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184 */
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185 if (arg)
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186 return COST_MAX;
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187
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188 cost = condition.inlineCost(ics);
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189
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190 /* Specifically allow:
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191 * if (condition)
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192 * return exp1;
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193 * else
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194 * return exp2;
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195 * Otherwise, we can't handle return statements nested in if's.
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196 */
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197
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198 if (elsebody && ifbody &&
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199 ifbody.isReturnStatement() &&
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200 elsebody.isReturnStatement())
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201 {
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202 cost += ifbody.inlineCost(ics);
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203 cost += elsebody.inlineCost(ics);
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204 //printf("cost = %d\n", cost);
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205 }
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206 else
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207 {
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208 ics.nested += 1;
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209 if (ifbody)
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210 cost += ifbody.inlineCost(ics);
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211 if (elsebody)
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212 cost += elsebody.inlineCost(ics);
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213 ics.nested -= 1;
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214 }
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215 return cost;
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216 }
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217
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218 override Expression doInline(InlineDoState ids)
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219 {
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220 Expression econd;
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221 Expression e1;
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222 Expression e2;
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223 Expression e;
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224
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225 assert(!arg);
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226 econd = condition.doInline(ids);
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227 assert(econd);
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228 if (ifbody)
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229 e1 = ifbody.doInline(ids);
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230 else
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231 e1 = null;
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232 if (elsebody)
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233 e2 = elsebody.doInline(ids);
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234 else
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235 e2 = null;
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236 if (e1 && e2)
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237 {
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238 e = new CondExp(econd.loc, econd, e1, e2);
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239 e.type = e1.type;
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240 }
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241 else if (e1)
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242 {
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243 e = new AndAndExp(econd.loc, econd, e1);
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244 e.type = Type.tvoid;
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245 }
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246 else if (e2)
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247 {
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248 e = new OrOrExp(econd.loc, econd, e2);
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249 e.type = Type.tvoid;
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250 }
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251 else
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252 {
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253 e = econd;
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254 }
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255 return e;
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256 }
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257
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258 override Statement inlineScan(InlineScanState* iss)
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259 {
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260 condition = condition.inlineScan(iss);
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261 if (ifbody)
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262 ifbody = ifbody.inlineScan(iss);
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263 if (elsebody)
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264 elsebody = elsebody.inlineScan(iss);
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265 return this;
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266 }
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267
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268 override void toIR(IRState* irs)
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269 {
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270 elem* e;
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271 Blockx* blx = irs.blx;
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272
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273 //printf("IfStatement::toIR('%s')\n", condition.toChars());
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274
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275 IRState mystate = IRState(irs, this);
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276
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277 // bexit is the block that gets control after this IfStatement is done
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278 block* bexit = mystate.breakBlock ? mystate.breakBlock : block_calloc();
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279
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280 incUsage(irs, loc);
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281 static if (false) {
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282 if (match)
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283 {
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284 /* Generate:
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285 * if (match = RTLSYM_IFMATCH(string, pattern)) ...
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286 */
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287 assert(condition.op == TOK.TOKmatch);
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288 e = matchexp_toelem(cast(MatchExp)condition, &mystate, RTLSYM.RTLSYM_IFMATCH);
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289 Symbol *s = match.toSymbol();
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290 symbol_add(s);
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291 e = el_bin(OPeq, TYnptr, el_var(s), e);
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292 }
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293 else
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294 {
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295 e = condition.toElem(&mystate);
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296 }
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297 } else {
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298 e = condition.toElem(&mystate);
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299 }
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300 block_appendexp(blx.curblock, e);
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301 block* bcond = blx.curblock;
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302 block_next(blx, BC.BCiftrue, null);
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303
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304 list_append(&bcond.Bsucc, blx.curblock);
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305 if (ifbody)
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306 ifbody.toIR(&mystate);
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307
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308 list_append(&blx.curblock.Bsucc, bexit);
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309
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310 if (elsebody)
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311 {
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312 block_next(blx, BC.BCgoto, null);
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313 list_append(&bcond.Bsucc, blx.curblock);
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314 elsebody.toIR(&mystate);
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315 list_append(&blx.curblock.Bsucc, bexit);
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316 }
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317 else
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318 list_append(&bcond.Bsucc, bexit);
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319
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320 block_next(blx, BC.BCgoto, bexit);
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321 }
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322 }
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