CFG: add throwing links from calls to out?

Author: kripken

src/cfg/cfg-traversal.h

@@ -161,26 +161,21 @@ struct CFGWalker : public PostWalker<SubType, VisitorType> {
   // exit blocks to flow to.
   bool hasSyntheticExit = false;
 
+  // Given a basic block, add a link to the exit block, indicating this block
+  // can reach the outside (unwind).
+  void linkToExit(BasicBlock* block) {
+    // TODO simplify exit/hasSynth
+    if (!hasSyntheticExit) {
+      exit = makeBasicBlock();
+      hasSyntheticExit = true;
+    }
+    link(block, exit);
+  }
+
   static void doEndReturn(SubType* self, Expression** currp) {
     auto* last = self->currBasicBlock;
     self->startUnreachableBlock();
-    if (!self->exit) {
-      // This is our first exit block and may be our only exit block, so just
-      // set it.
-      self->exit = last;
-    } else if (!self->hasSyntheticExit) {
-      // We now have multiple exit blocks, so we need to create a synthetic one.
-      // It will be added to the list of basic blocks at the end of the
-      // function.
-      auto* lastExit = self->exit;
-      self->exit = self->makeBasicBlock();
-      self->link(lastExit, self->exit);
-      self->link(last, self->exit);
-      self->hasSyntheticExit = true;
-    } else {
-      // We already have a synthetic exit block. Just link it up.
-      self->link(last, self->exit);
-    }
+    self->linkToExit(last);
   }
 
   static void doStartIfTrue(SubType* self, Expression** currp) {
@@ -354,6 +349,11 @@ struct CFGWalker : public PostWalker<SubType, VisitorType> {
       // the outside) can only happen at the end of basic blocks.
       auto* last = self->currBasicBlock;
       self->link(last, self->startBasicBlock());
+
+      if (!self->ignoreBranchesOutsideOfFunc) {
+        // Add a branch to the outside of the func.
+        self->linkToExit(last);
+      }
     }
   }