Fix leaking arg slots on tail calls. Closes #160.

Author: graydon

src/Makefile

@@ -533,6 +533,7 @@ TEST_XFAILS_LLVM := $(TASK_XFAILS) \
                       str-concat.rs \
                       str-idx.rs \
                       tag.rs \
+                      tail-call-arg-leak.rs \
                       tail-cps.rs \
                       tail-direct.rs \
                       task-comm.rs \

src/boot/me/trans.ml

@@ -4219,6 +4219,8 @@ let trans_visitor
                (Printf.sprintf "copy args for tail call to %s" (logname ())));
       copy_fn_args true true CLONE_none call;
       drop_slots_at_curr_stmt();
+      iflog (fun _ -> annotate "drop args");
+      iter_arg_slots cx (current_fn()) callee_drop_slot;
       abi.Abi.abi_emit_fn_tail_call (emitter())
         (force_sz (current_fn_callsz()))
         caller_argsz callee_code callee_argsz;

src/test/run-pass/tail-call-arg-leak.rs

@@ -0,0 +1,11 @@
+// use of tail calls causes arg slot leaks, issue #160.
+
+fn inner(str dummy, bool b) {
+  if (b) {
+    be inner(dummy, false);
+  }
+}
+
+fn main() {
+  inner("hi", true);
+}