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Lab5-函数和变量

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本文字数： 5.8k 阅读时长 ≈ 5 分钟

实现功能

本次实验完成了以下功能：

  1. 函数定义与调用
  2. 局部变量

实验设计

本次实验参照助教在文档中的提示，对符号表做了如下设计。注意本次实验中符号表不再依赖 Symbol 和 Type 包，而是直接存储 String 对 LLVMValueRef 的映射。

本次实验重新设计了 LLVMVisitor 类，部分代码如下：

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public class LLVMIRVisitor extends SysYParserBaseVisitor<LLVMValueRef> {
	private final LLVMModuleRef module = LLVMModuleCreateWithName("module");
	private final LLVMBuilderRef builder = LLVMCreateBuilder();
	private final LLVMTypeRef i32Type = LLVMInt32Type();
	private final LLVMTypeRef voidType = LLVMVoidType();
	private final LLVMValueRef zero = LLVMConstInt(i32Type, 0, 0);
	
	public LLVMIRVisitor() {
		LLVMInitializeCore(LLVMGetGlobalPassRegistry());
		LLVMLinkInMCJIT();
		LLVMInitializeNativeAsmPrinter();
		LLVMInitializeNativeAsmParser();
		LLVMInitializeNativeTarget();
	}
	
	@Override
	public LLVMValueRef visitTerminal(TerminalNode node) {
		if (symbolType == SysYParser.INTEGR_CONST) {
			return LLVMConstInt(i32Type, number, 0);
		}
		return super.visitTerminal(node);
	}
    
	@Override
	public LLVMValueRef visitFuncDef(SysYParser.FuncDefContext ctx) {
		int paramsCount;
		
		PointerPointer<Pointer> paramsTypes = new PointerPointer<>(paramsCount);
		String retTypeName = ctx.funcType().getText();
		LLVMTypeRef retType = getTypeRef(retTypeName);
		LLVMTypeRef functionType = LLVMFunctionType(retType, paramsTypes, paramsCount, 0);
		String functionName = ctx.IDENT().getText();
		LLVMValueRef function = LLVMAddFunction(module, functionName, functionType);
		LLVMBasicBlockRef entry = LLVMAppendBasicBlock(function, functionName + "_entry");
		LLVMPositionBuilderAtEnd(builder, entry);
		
		for (int i = 0; i < paramsCount; ++i) {
			SysYParser.FuncFParamContext funcFParamContext = ctx.funcFParams().funcFParam(i);
			LLVMTypeRef paramType = getTypeRef(paramTypeName);
			LLVMValueRef varPointer = LLVMBuildAlloca(builder, paramType, "pointer_" + varName);
			currentScope.define(varName, varPointer);
			LLVMValueRef argValue = LLVMGetParam(function, i);
			LLVMBuildStore(builder, argValue, varPointer);
		}
        
		return function;
	}
	
	@Override
	public LLVMValueRef visitVarDecl(SysYParser.VarDeclContext ctx) {
		for (SysYParser.VarDefContext varDefContext : ctx.varDef()) {
			LLVMValueRef varPointer = LLVMBuildAlloca(builder, varType, "pointer_" + varName);
			
			if (varDefContext.ASSIGN() != null) {
				SysYParser.ExpContext expContext = varDefContext.initVal().exp();
				if (expContext != null) {
					LLVMValueRef initVal = visit(expContext);
					LLVMBuildStore(builder, initVal, varPointer);
				} else {
					int initValCount = varDefContext.initVal().initVal().size();
					LLVMValueRef[] initArray = new LLVMValueRef[elementCount];
					// fill in initArray
					buildGEP(elementCount, varPointer, initArray);
				}
			}
			
			currentScope.define(varName, varPointer);
		}
		
		return null;
	}
	
	private void buildGEP(int elementCount, LLVMValueRef varPointer, LLVMValueRef[] initArray) {
        // 这里展示的是方法的全部代码
		LLVMValueRef[] arrayPointer = new LLVMValueRef[2];
		arrayPointer[0] = zero;
		for (int i = 0; i < elementCount; i++) {
			arrayPointer[1] = LLVMConstInt(i32Type, i, 0);
			PointerPointer<LLVMValueRef> indexPointer = new PointerPointer<>(arrayPointer);
			LLVMValueRef elementPtr = LLVMBuildGEP(builder, varPointer, indexPointer, 2, "GEP_" + i);
			LLVMBuildStore(builder, initArray[i], elementPtr);
		}
	}
    
	@Override
	public LLVMValueRef visitLValExp(SysYParser.LValExpContext ctx) {
		LLVMValueRef lValPointer = this.visitLVal(ctx.lVal());
		return LLVMBuildLoad(builder, lValPointer, ctx.lVal().getText());
	}
	
	@Override
	public LLVMValueRef visitFuncCallExp(SysYParser.FuncCallExpContext ctx) {
		String functionName = ctx.IDENT().getText();
		LLVMValueRef function = currentScope.resolve(functionName);
		PointerPointer<Pointer> args = null;
		return LLVMBuildCall(builder, function, args, argsCount, "");
	}
	
	@Override
	public LLVMValueRef visitReturnStmt(SysYParser.ReturnStmtContext ctx) {
		LLVMValueRef result;
		return LLVMBuildRet(builder, result);
	}
}

测试用例

样例输入
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int f(int i){
    return i;
}

void g() {
	int j = 1 + 5;
	return;
}

void func() {
}

int main(){
    int a = 1;
    int array[5] = {1, 2, 3};
    array[3] = a;
    array[4] = a + 5;
    g();
    return f(a * array[4]);
}
样例输出
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; ModuleID = 'module'
source_filename = "module"

define i32 @f(i32 %0) {
f_entry:
  %pointer_i = alloca i32, align 4
  store i32 %0, i32* %pointer_i, align 4
  %i = load i32, i32* %pointer_i, align 4
  ret i32 %i
}

define void @g() {
g_entry:
  %pointer_j = alloca i32, align 4
  store i32 6, i32* %pointer_j, align 4
  ret void
}

define void @func() {
func_entry:
  ret void
}

define i32 @main() {
main_entry:
  %pointer_a = alloca i32, align 4
  store i32 1, i32* %pointer_a, align 4
  %pointer_array = alloca <5 x i32>, align 32
  %GEP_0 = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 0
  store i32 1, i32* %GEP_0, align 4
  %GEP_1 = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 1
  store i32 2, i32* %GEP_1, align 4
  %GEP_2 = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 2
  store i32 3, i32* %GEP_2, align 4
  %GEP_3 = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 3
  store i32 0, i32* %GEP_3, align 4
  %GEP_4 = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 4
  store i32 0, i32* %GEP_4, align 4
  %"pointer_array[3]" = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 3
  %a = load i32, i32* %pointer_a, align 4
  store i32 %a, i32* %"pointer_array[3]", align 4
  %"pointer_array[4]" = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 4
  %a1 = load i32, i32* %pointer_a, align 4
  %add_ = add i32 %a1, 5
  store i32 %add_, i32* %"pointer_array[4]", align 4
  call void @g()
  %a2 = load i32, i32* %pointer_a, align 4
  %"pointer_array[4]3" = getelementptr <5 x i32>, <5 x i32>* %pointer_array, i32 0, i32 4
  %"array[4]" = load i32, i32* %"pointer_array[4]3", align 4
  %mul_ = mul i32 %a2, %"array[4]"
  %0 = call i32 @f(i32 %mul_)
  ret i32 %0
}