Fix recursive usage of emitCond() (#55)

Summary:
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.

Pull Request resolved: #55

Reviewed By: kddnewton

Differential Revision: D104095042

Pulled By: alexmalyshev

fbshipit-source-id: fcc31e33e06708a3be4a751daef41c231e5450fd

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);
   }