public void compile(
List<FrameVar> locals, List<DynamicVar> dynamics, CodeBox code, boolean isLast) {
// The expressions matched by the case arms are set in the stack frame as
// locals...
int base = locals.length();
int index = 0;
for (AST exp : exps) {
exp.compile(locals, dynamics, code, false);
locals = locals.cons(new FrameVar("$case-" + (index++), locals.length()));
code.add(new SetFrame(getLineStart(), locals.length() - 1), locals, dynamics);
code.add(new Pop(getLineStart()), locals, dynamics);
}
compileArms(base, locals, dynamics, code, isLast);
}
public void compileArms(
int varIndex,
List<FrameVar> locals,
List<DynamicVar> dynamics,
CodeBox code,
boolean isLast) {
boolean useSwitchTable = isDisjointArms() && arms.length > 3;
SwitchTable switchTableInstr = new SwitchTable(getLineStart(), varIndex);
if (useSwitchTable) code.add(switchTableInstr, locals, dynamics);
// Define the dynamic vars up front ... then remove them at the end...
// Compile each arm independently...
Vector<CodeBox> armCode = new Vector<CodeBox>();
Vector<HashSet<String>> armBV = new Vector<HashSet<String>>();
Vector<HashSet<String>> armDV = new Vector<HashSet<String>>();
for (BArm arm : arms) {
// Work out which variables bound by patterns should be local and which
// should be dynamic...
HashSet<String> DV = new HashSet<String>();
HashSet<String> BV = new HashSet<String>();
for (Pattern p : arm.patterns) p.vars(BV);
arm.exp.DV(DV);
arm.guard.DV(DV);
armBV.add(BV);
armDV.add(DV);
}
for (int i = 0; i < arms.length; i++) {
BArm arm = arms[i];
HashSet<String> BV = armBV.get(i);
HashSet<String> DV = armDV.get(i);
List<FrameVar> armLocals = locals;
List<DynamicVar> armDynamics = dynamics;
CodeBox instrs = new CodeBox("", 0);
// We have just failed to here so remove the dynamic variables from the
// previous arm...
if (i > 0) {
for (String v : armBV.get(i - 1)) {
if (armDV.get(i - 1).contains(v)) {
instrs.add(new PopDynamic(getLineStart()), locals, dynamics);
dynamics = dynamics.getTail();
}
}
}
for (String v : BV) {
if (DV.contains(v)) {
armDynamics = armDynamics.map(DynamicVar::incDynamic).cons(new DynamicVar(v, 0));
instrs.add(new Null(getLineStart()), locals, dynamics);
instrs.add(new NewDynamic(getLineStart()), locals, dynamics);
} else armLocals = armLocals.cons(new FrameVar(v, armLocals.length()));
}
arm.compile(varIndex, armLocals, armDynamics, instrs, isLast && i == arms.length - 1);
for (String v : BV) {
if (DV.contains(v)) {
instrs.add(new PopDynamic(getLineStart()), locals, dynamics);
dynamics = dynamics.getTail();
}
}
armCode.add(instrs);
}
// Now insert the TRY...SKIP instructions between the arms...
for (int i = 0; i < armCode.size(); i++) {
int length = code.getCode().size();
instrs.patterns.Try tryArm = new instrs.patterns.Try(getLineStart(), 0, i == 0);
code.add(tryArm, locals, dynamics);
int base = code.getCode().size();
CodeBox armCodeBox = armCode.get(i);
if (useSwitchTable) switchTableInstr.processArm(arms[i], code.getCode().size());
for (Instr instr : armCodeBox.getCode()) {
if (instr instanceof Goto) {
Goto g = (Goto) instr;
g.setAddress(g.getAddress() + base);
}
code.add(
instr,
armCodeBox.getLocalsAt(armCodeBox.indexOf(instr)),
armCodeBox.getDynamicsAt(armCodeBox.indexOf(instr)));
}
// Jump over the rest of the case arms and the end error message...
int distance = distance(armCode, i + 1) + 2;
Skip jmp = new Skip(getLineStart(), distance);
code.add(jmp, locals, dynamics);
int offset = code.getCode().size() - length;
tryArm.setOffset(offset - 1);
if (useSwitchTable) switchTableInstr.processError(arms[i], offset - 1);
}
// Add in the error at the end of the case...
code.add(new instrs.patterns.CaseError(getLineStart(), this, varIndex), locals, dynamics);
}