simplify jumps

vyper/venom/passes/simplify_cfg.py

@@ -23,14 +23,33 @@ def _merge_blocks(self, a: IRBasicBlock, b: IRBasicBlock):
             n.remove_cfg_in(b)
             n.add_cfg_in(a)
 
+        self.ctx.basic_blocks.remove(b)
+
+    def _merge_jump(self, a: IRBasicBlock, b: IRBasicBlock):
+        next = b.cfg_out.first()
+        jump_inst = a.instructions[-1]
+        assert b.label in jump_inst.operands, f"{b.label} {jump_inst.operands}"
+        jump_inst.operands[jump_inst.operands.index(b.label)] = next.label
+        a.remove_cfg_out(b)
+        a.add_cfg_out(next)
+        next.remove_cfg_in(b)
+        next.add_cfg_in(a)
+        self.ctx.basic_blocks.remove(b)
+
     def _collapse_chained_blocks_r(self, bb: IRBasicBlock):
         if len(bb.cfg_out) == 1:
             next = bb.cfg_out.first()
             if len(next.cfg_in) == 1:
                 self._merge_blocks(bb, next)
-                self.ctx.basic_blocks.remove(next)
                 self._collapse_chained_blocks_r(bb)
                 return
+        elif len(bb.cfg_out) == 2:
+            bb_out = bb.cfg_out.copy()
+            for next in bb_out:
+                if len(next.cfg_in) == 1 and len(next.cfg_out) == 1 and len(next.instructions) == 1:
+                    self._merge_jump(bb, next)
+                    self._collapse_chained_blocks_r(bb)
+                    return
 
         if bb in self.visited:
             return