fix UB in dom tree builder

src/CFGraph/CFGraph.h

@@ -74,12 +74,6 @@ namespace SAPFOR
         const std::vector<BasicBlock*>& getPrev() const { return prev; }
         BasicBlock* getDom() const 
         {
-            if (!directDominator)
-            {
-                __spf_print(1, "%s\n", "the dominator tree was built with an error or was not built at all");
-                printInternalError(convertFileName(__FILE__).c_str(), __LINE__);
-            }
-
             return directDominator; 
         }
 

src/CFGraph/IR_domTree.cpp

@@ -64,6 +64,8 @@ namespace SAPFOR {
             int w = vertex[i];
 
             for (BasicBlock* v : vertices[w]->getPrev()) {
+                if (dfs_num[v] == -1)
+                    continue;
                 int u = Eval(dfs_num[v]);
 
                 if (semi[u] < semi[w])