From 0025ff968d71ab7a8acab369441ee4b17b753966 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 30 Jun 2011 08:21:36 -0600
Subject: [PATCH] fix JIT bug  that caused incorrect compilation of a non-tail
 call as  a self non-tail call (but why hasn't this deep and old bug caused 
 more trouble over the years?)

---
 src/racket/src/jit.c      | 11 ++++++++---
 src/racket/src/jitstate.c |  3 +++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/racket/src/jit.c b/src/racket/src/jit.c
index 2c2d82e00a..12a394e2b3 100644
--- a/src/racket/src/jit.c
+++ b/src/racket/src/jit.c
@@ -1513,7 +1513,7 @@ static int generate_branch(Scheme_Object *obj, mz_jit_state *jitter, int is_tail
   GC_CAN_IGNORE jit_insn *ref2;
   int pushed_marks;
   int nsrs, nsrs1, g1, g2, amt, need_sync, flostack, flostack_pos;
-  int else_is_empty = 0, i, can_chain_branch, chain_true, chain_false;
+  int else_is_empty = 0, i, can_chain_branch, chain_true, chain_false, old_self_pos;
 #ifdef NEED_LONG_JUMPS
   int then_short_ok, else_short_ok;
 #else
@@ -1533,6 +1533,8 @@ static int generate_branch(Scheme_Object *obj, mz_jit_state *jitter, int is_tail
   else_short_ok = (is_short(branch->fbranch, 32) > 0);
 #endif
 
+  old_self_pos = jitter->self_pos;
+
   for_this_branch.addrs = addrs;
   for_this_branch.addrs_size = NUM_QUICK_INFO_ADDRS;
   for_this_branch.addrs_count = 0;
@@ -1648,6 +1650,9 @@ static int generate_branch(Scheme_Object *obj, mz_jit_state *jitter, int is_tail
   jitter->pushed_marks = pushed_marks;
   if (need_sync) mz_rs_sync_0();
 
+  if (old_self_pos != jitter->self_pos)
+    scheme_signal_error("internal error: self position moved across branch");
+
   /* False branch */
   mz_CLEAR_R0_STATUS();
   scheme_mz_runstack_saved(jitter);
@@ -3190,7 +3195,7 @@ static int do_generate_closure(mz_jit_state *jitter, void *_data)
                                      ? NATIVE_IS_SINGLE_RESULT
                                        : 0)));
 	if (SAME_OBJ(lr->procs[pos], (Scheme_Object *)data)) {
-	  self_pos = i;
+          self_pos = i;
 	}
       } else {
 #ifdef USE_FLONUM_UNBOXING
@@ -3252,7 +3257,7 @@ static int do_generate_closure(mz_jit_state *jitter, void *_data)
   jitter->closure_to_args_delta = to_args;
   jitter->example_argc = argc;
   jitter->example_argv = argv;
-  
+
   /* Generate code for the body: */
   jitter->need_set_rs = 1;
   r = scheme_generate(data->code, jitter, 1, 1, 1, JIT_R0, NULL); /* no need for sync */
diff --git a/src/racket/src/jitstate.c b/src/racket/src/jitstate.c
index 6c61c1a6bb..047492f3e2 100644
--- a/src/racket/src/jitstate.c
+++ b/src/racket/src/jitstate.c
@@ -476,6 +476,9 @@ int scheme_mz_compute_runstack_restored(mz_jit_state *jitter, int adj, int skip)
         c >>= 2;
         if (c > 0)
           amt += c;
+        else {
+          if (adj) jitter->self_pos += c;
+        }
       }
     } else if (c & 0x2) {
       /* single procedure */