fix UB in dom tree builder

src/CFGraph/CFGraph.h

@@ -73,13 +73,7 @@ namespace SAPFOR
         const std::vector<BasicBlock*>& getNext() const { return next; }
         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])
@@ -97,4 +99,4 @@ namespace SAPFOR {
     void buildDominatorTree(std::vector<BasicBlock*>& blocks) {
         DominatorFinder finder(blocks);
     }
-}
+}