bug fixes

Have to be seal BBs as soon as possible - will need to review this carefully

Author: dibyendumajumdar

optvm/src/main/java/com/compilerprogramming/ezlang/compiler/CompiledFunction.java

@@ -265,11 +265,13 @@ private void compileIf(AST.IfElseStmt ifElseStmt) {
         issa.sealBlock(currentBlock);
         assert vstackEmpty();
         startBlock(ifBlock);
+        issa.sealBlock(ifBlock);
         compileStatement(ifElseStmt.ifStmt);
         if (!isBlockTerminated(currentBlock))
             jumpTo(exitBlock);
         if (elseBlock != null) {
             startBlock(elseBlock);
+            issa.sealBlock(elseBlock);
             compileStatement(ifElseStmt.elseStmt);
             if (!isBlockTerminated(currentBlock))
                 jumpTo(exitBlock);
@@ -663,7 +665,7 @@ private void codeStoreAppend() {
     private void codeArg(Operand.LocalRegisterOperand target) {
         var newtarget = (Operand.RegisterOperand) issa.write(target);
         var insn = new Instruction.ArgInstruction(newtarget);
-        issa.recordDef(target, insn);
+        issa.recordDef(newtarget, insn);
         code(insn);
     }
 
@@ -694,7 +696,8 @@ private void codeCall(int newBase,
                           Operand.RegisterOperand targetOperand,
                           Type.TypeFunction calleeType,
                           Operand.RegisterOperand ...arguments) {
-        targetOperand = (Operand.RegisterOperand) issa.write(targetOperand);
+        if (targetOperand != null)
+            targetOperand = (Operand.RegisterOperand) issa.write(targetOperand);
         Operand.RegisterOperand args[] = new Operand.RegisterOperand[arguments.length];
         for (int i = 0; i < args.length; i++) {
             args[i] = (Operand.RegisterOperand) issa.read(arguments[i]);