libfpvm: make op_not a regular operator and implement it in all cases

We can substitute  !X  it with  X == 0. This catches cases where boolean
not is used algorithmically and not directly with if.

software/include/fpvm/ast.h

@@ -47,7 +47,7 @@ enum ast_op {
 	op_min,
 	op_max,
 	op_int,
-	op_vops,	/* virtual operations start here */
+	op_not,
 };
 
 /* maximum supported arity is 3 */

software/libfpvm/fpvm.c

@@ -522,6 +522,12 @@ static int compile(struct fpvm_fragment *fragment, int reg, struct ast_node *nod
 			return FPVM_INVALID_REG;
 		ADD_ISN(FPVM_OPCODE_TSIGN, opa, opb, reg);
 		break;
+	case op_not:
+		opb = REG_CONST(0);
+		if(opb == FPVM_INVALID_REG)
+			return FPVM_INVALID_REG;
+		ADD_ISN(FPVM_OPCODE_EQUAL, opa, opb, reg);
+		break;
 	default:
 		/* Normal case */
 		opcode = operator2opcode(node->op);