236 lines
6.6 KiB
Java
236 lines
6.6 KiB
Java
public class CodegenImpl implements Codegen {
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private int labelCounter = 0;
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public CodegenImpl() {}
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public String codegen(Program p) throws CodegenException {
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StringBuilder builder = new StringBuilder();
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Declaration main = null;
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for (Declaration d : p.decls) {
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if (main == null) {
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main = d;
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}
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builder.append(compileDeclaration(d));
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}
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return "call " + String.format("%s_%d\n", main.id, main.numOfArgs)
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+ "li a7,10\n"
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+ "ecall\n"
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+ builder.toString();
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}
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private String generateLabel() {
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return String.format("branch_%d", labelCounter++);
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}
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public String compileDeclaration(Declaration d) throws CodegenException {
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return String.format("%s_%d:\n", d.id, d.numOfArgs)
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+ compileExp(d.body)
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+ "ret\n";
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}
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public String compileExp(Exp e) throws CodegenException {
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if (e instanceof IntLiteral) {
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return String.format("li a0,%d\n", ((IntLiteral) e).n);
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} else if (e instanceof If) {
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If eIf = (If) e;
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String thenLabel = generateLabel();
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String elseLabel = generateLabel();
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String finalizeLabel = generateLabel();
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return compileFullComp(eIf.l, eIf.r, eIf.comp, thenLabel, elseLabel)
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+ thenLabel + ": " + compileExp(eIf.thenBody)
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+ "j " + finalizeLabel + "\n"
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+ elseLabel + ": " + compileExp(eIf.elseBody)
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+ finalizeLabel + ": " + "lw s1,(sp)\n"
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+ "addi sp,sp,4\n";
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} else if (e instanceof Binexp) {
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Binexp b = (Binexp) e;
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return compileExp(b.l)
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+ "sw s1,-4(sp)\n"
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+ "addi sp,sp,-4\n"
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+ "mv s1,a0\n"
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+ compileExp(b.r)
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+ "mv t1,a0\n"
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+ compileExpBinop(b.binop)
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+ "lw s1,(sp)\n"
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+ "addi sp,sp,4\n";
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} else if (e instanceof Variable) {
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int offset = ((Variable) e).x - 1;
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return String.format("lw a0,%d(s0)\n", offset * 4);
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} else if (e instanceof Invoke) {
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return compileCall((Invoke) e, false);
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} else if (e instanceof Seq) {
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String result = "";
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Seq statements = (Seq) e;
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if (statements.r instanceof Invoke) {
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// tail call
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result = compileCall((Invoke) statements.r, true);
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} else {
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result = compileExp(statements.r);
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}
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return compileExp(statements.l) + result;
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} else if (e instanceof While) {
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While eWhile = (While) e;
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String startLabel = generateLabel();
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String bodyLabel = generateLabel();
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String exitLabel = generateLabel();
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return "sw s2,-4(sp)\n"
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+ "sw s3,-8(sp)\n"
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+ "addi sp,sp,-8\n"
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+ "la s2," + startLabel + "\n"
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+ "la s3," + exitLabel + "\n"
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+ startLabel + ": " + compileFullComp(eWhile.l, eWhile.r, eWhile.comp, bodyLabel, exitLabel)
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+ bodyLabel + ": " + compileExp(eWhile.body)
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+ "lw s1,(sp)\n"
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+ "addi sp,sp,4\n"
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+ "j " + startLabel + "\n"
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+ exitLabel + ": lw s1,(sp)\n"
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+ "lw s3,4(sp)\n"
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+ "lw s2,8(sp)\n"
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+ "addi sp,sp,12\n";
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} else if (e instanceof RepeatUntil) {
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RepeatUntil eUntil = (RepeatUntil) e;
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String compLabel = generateLabel();
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String bodyLabel = generateLabel();
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String exitLabel = generateLabel();
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String contLabel = generateLabel();
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String breakLabel = generateLabel();
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return "sw s2,-8(sp)\n"
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+ "sw s3,-4(sp)\n"
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+ "addi sp,sp,-8\n"
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+ "la s2," + contLabel + "\n"
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+ "la s3," + breakLabel + "\n"
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+ bodyLabel + ": " + compileExp(eUntil.body)
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+ contLabel + ": sw s4,-4(sp)\n"
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+ "addi sp,sp,-4\n"
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+ "mv s4,a0\n"
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+ compileFullComp(eUntil.l, eUntil.r, eUntil.comp, exitLabel, compLabel)
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+ compLabel + ": lw s1,(sp)\n"
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+ "lw s4,4(sp)\n"
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+ "addi sp,sp,8\n"
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+ "j " + bodyLabel + "\n"
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+ breakLabel + ": sw s1,-8(sp)\n"
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+ "sw s4,-4(sp)\n"
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+ "addi sp,sp,-8\n"
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+ "mv s4,a0\n"
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+ exitLabel + ": lw s1,(sp)\n"
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+ "mv a0,s4\n" // body result to accumulator
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+ "lw s4,4(sp)\n" // restore previous s4
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+ "lw s2,8(sp)\n"
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+ "lw s3,12(sp)\n"
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+ "addi sp,sp,16\n";
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} else if (e instanceof Assign) {
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Assign assign = (Assign) e;
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return compileExp(assign.e)
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+ String.format("sw a0,%d(s0)\n", (assign.x - 1) * 4);
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} else if (e instanceof Continue) {
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return "jr s2\n";
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} else if (e instanceof Break) {
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return "jr s3\n";
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} else if (e instanceof Skip) {
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return "nop\n";
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}
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throw new CodegenException("Unsupported expression!");
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}
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public String compileCall(Invoke call, boolean tailCall) throws CodegenException {
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int argLen = call.args.size();
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String methodLabel = String.format("%s_%d", call.name, argLen);
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StringBuilder builder = new StringBuilder();
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// Store return address
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builder.append("sw ra,-4(sp)\n");
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builder.append("mv t0,sp\n");
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// shuffle stack pointer to start of arguments
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builder.append(String.format("addi sp,sp,-%d\n", (argLen + 1) * 4));
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builder.append("sw t0,-8(sp)\n"); // store old stack pointer (top of frame)
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for (int i = argLen - 1; i >= 0; i--) {
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Exp argExp = call.args.get(i);
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builder.append(compileExp(argExp));
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builder.append(
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String.format("sw a0,%d(sp)\n", i*4)
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);
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}
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// push old frame pointer
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builder.append("sw s0,-4(sp)\n");
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builder.append("addi sp,sp,-8\n");
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builder.append(
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// set frame pointer to start of arguments
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"addi s0,sp,8\n"
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+ "call " + methodLabel + "\n"
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// restore stack to frame pointer - 8 (bottom of frame)
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// this ensures any stack growth inside the method is undone
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+ "addi sp,s0,-8\n"
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// restore old frame pointer & stack pointer
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+ "lw s0,4(sp)\n"
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+ "lw sp,(sp)\n"
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// restore return address of caller
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+ "lw ra,-4(sp)\n"
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);
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return builder.toString();
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}
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public String compileFullComp(Exp left, Exp right, Comp c, String successLabel, String failLabel) throws CodegenException {
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return compileExp(left)
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+ "sw s1,-4(sp)\n"
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+ "addi sp,sp,-4\n"
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+ "mv s1,a0\n"
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+ compileExp(right)
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+ "mv t1,a0\n"
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+ compileComp(c, successLabel, failLabel);
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}
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public String compileComp(Comp c, String thenLabel, String elseLabel) throws CodegenException {
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String instruction = "";
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if (c instanceof Equals) {
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instruction = "beq";
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} else if (c instanceof Less) {
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instruction = "blt";
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} else if (c instanceof LessEq) {
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instruction = "ble";
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} else if (c instanceof Greater) {
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instruction = "bgt";
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} else if (c instanceof GreaterEq) {
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instruction = "bge";
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} else {
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throw new CodegenException("Unsupported comparison!");
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}
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return String.format("%s s1,t1,%s\nb %s\n", instruction, thenLabel, elseLabel);
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}
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public String compileExpBinop(Binop bin) throws CodegenException {
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if (bin instanceof Plus) {
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return "add a0,s1,t1\n";
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} else if (bin instanceof Minus) {
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return "sub a0,s1,t1\n";
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} else if (bin instanceof Times) {
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return "mul a0,s1,t1\n";
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} else if (bin instanceof Div) {
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return "div a0,s1,t1\n";
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}
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throw new CodegenException("Unsupported bin-op! " + bin);
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}
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}
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