Fix recursive usage of emitCond()

When the do_bb1() or do_bb2() functions called by emitCond() themselves call
emitCond(), the outer conditional will grab the wrong blocks for its resulting
Phi.  It'll use the first block of their inner CFGs instead of the last one.

Author: alexmalyshev

cinderx/Jit/hir/simplify.cpp

@@ -173,18 +173,21 @@ struct Env {
     block = bb1;
     cursor = bb1->end();
     Register* bb1_reg = do_bb1();
+    // do_bb1() might have created more blocks, use the final one.
+    BasicBlock* bb1_end = block;
     emit<Branch>(tail);
 
     block = bb2;
     cursor = bb2->end();
     Register* bb2_reg = do_bb2();
+    BasicBlock* bb2_end = block;
     emit<Branch>(tail);
 
     block = tail;
     cursor = tail->begin();
     std::unordered_map<BasicBlock*, Register*> phi_srcs{
-        {bb1, bb1_reg},
-        {bb2, bb2_reg},
+        {bb1_end, bb1_reg},
+        {bb2_end, bb2_reg},
     };
     return emit<Phi>(phi_srcs);
   }