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namespace Q1.Compiler.visitors;
public partial class CCompilerVisitor
{
public override string? VisitBlock(CGrammarParser.BlockContext context)
{
this.EnterScope();
this.VisitChildren(context);
this.ExitScope();
return null;
}
public override string? VisitReturnStatement(CGrammarParser.ReturnStatementContext context)
{
if (context.expression() != null)
{
string expression = this.VisitExpression(context.expression());
this.Instruction($"mov {expression}, V0", "return value");
this.Instruction($"ret");
}
else
this.Instruction("ret");
return null;
}
public override string? VisitIfStatement(CGrammarParser.IfStatementContext context)
{
string cond = this.VisitExpression(context.expression());
string endBranch = this.GenerateBranchLabel("end");
if (context.@else != null)
{
this.Instruction($"bz {cond}", "check if condition");
// Else branch is first since it saves us from having to perform a NOT operation.
// If cond, jump to then, else fall through to else, then jump to end
string thenBranch = this.GenerateBranchLabel("then");
this.Instruction($"jmp {thenBranch}");
this.GeneratedComment("if failed");
if (context.@else != null)
this.Visit(context.@else);
this.Instruction($"jmp {endBranch}");
this.Branch(thenBranch, "if succeeded");
this.Visit(context.then);
}
else
{
this.Instruction($"not {cond}");
this.Instruction($"bz", "check if condition");
this.Instruction($"jmp {endBranch}", "if succeeds, continue, else jump to end");
this.Visit(context.then);
}
this.Branch(endBranch);
return null;
}
public override string? VisitForExprStatement(CGrammarParser.ForExprStatementContext context)
{
string bodyBranch = this.GenerateBranchLabel("body");
string endBranch = this.GenerateBranchLabel("end");
context.LoopBodyBranch = bodyBranch;
context.LoopEndBranch = endBranch;
this.EnterScope();
this.Visit(context.initializer);
this.Branch(bodyBranch);
string cond = this.VisitExpression(context.cond);
this.Instruction($"not {cond}");
this.Instruction($"bz");
this.Instruction($"jmp {endBranch}", "if for condition fails, jump to end");
this.Visit(context.body);
this.Visit(context.post);
this.Branch(endBranch);
this.ExitScope();
return null;
}
public override string? VisitForDeclStatement(CGrammarParser.ForDeclStatementContext context)
{
string bodyBranch = this.GenerateBranchLabel("body");
string endBranch = this.GenerateBranchLabel("end");
context.LoopBodyBranch = bodyBranch;
context.LoopEndBranch = endBranch;
this.EnterScope();
this.Visit(context.initializer);
this.Branch(bodyBranch);
string cond = this.VisitExpression(context.cond);
this.Instruction($"not {cond}");
this.Instruction($"bz");
this.Instruction($"jmp {endBranch}", "if for condition fails, jump to end");
this.Visit(context.body);
this.Visit(context.post);
this.Instruction($"jmp {bodyBranch}");
this.Branch(endBranch);
this.ExitScope();
return null;
}
public override string? VisitWhileStatement(CGrammarParser.WhileStatementContext context)
{
string bodyBranch = this.GenerateBranchLabel("body");
string endBranch = this.GenerateBranchLabel("end");
context.LoopBodyBranch = bodyBranch;
context.LoopEndBranch = endBranch;
this.Branch(bodyBranch);
string cond = this.VisitExpression(context.cond);
this.Instruction($"not {cond}");
this.Instruction($"bz");
this.Instruction($"jmp {endBranch}", "if while condition fails, jump to end");
this.Visit(context.body);
this.Instruction($"jmp {bodyBranch}");
this.Branch(endBranch);
return null;
}
public override string? VisitDoWhileStatement(CGrammarParser.DoWhileStatementContext context)
{
string bodyBranch = this.GenerateBranchLabel("body");
string endBranch = this.GenerateBranchLabel("end");
context.LoopBodyBranch = bodyBranch;
context.LoopEndBranch = endBranch;
this.Branch(bodyBranch);
this.Visit(context.body);
string cond = this.VisitExpression(context.cond);
this.Instruction($"bz {cond}");
this.Instruction($"jmp {bodyBranch}", "if while condition succeeds, jump back to start");
this.Branch(endBranch);
return null;
}
public override string? VisitBreakStatement(CGrammarParser.BreakStatementContext context)
{
if (context.LoopEndBranch == null)
throw new CompilerException("Cannot break, not inside loop with end");
this.Instruction($"jmp {context.LoopEndBranch}", "break");
return null;
}
public override string? VisitContinueStatement(CGrammarParser.ContinueStatementContext context)
{
if (context.LoopBodyBranch == null)
throw new CompilerException("Cannot skip body (continue), not inside loop with body");
this.Instruction($"jmp {context.LoopBodyBranch}", "continue");
return null;
}
}
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