From 318e86c7eb53999783c0c4a3c6796d1a723dd024 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Wed, 3 Feb 2010 14:55:56 +0100
Subject: [PATCH] Clean up frame depth checks and loop detection.

---
 src/lj_jit.h    |  1 +
 src/lj_record.c | 14 +++++++++-----
 src/lj_trace.c  |  3 ++-
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/lj_jit.h b/src/lj_jit.h
index 35595cd5..1e029182 100644
--- a/src/lj_jit.h
+++ b/src/lj_jit.h
@@ -231,6 +231,7 @@ typedef struct jit_State {
   int32_t loopunroll;	/* Unroll counter for loop ops in side traces. */
   int32_t tailcalled;	/* Number of successive tailcalls. */
   int32_t framedepth;	/* Current frame depth. */
+  int32_t retdepth;	/* Return frame depth (count of RETF). */
 
   MRef knum;		/* Pointer to chained array of KNUM constants. */
 
diff --git a/src/lj_record.c b/src/lj_record.c
index a32d19f0..682246d7 100644
--- a/src/lj_record.c
+++ b/src/lj_record.c
@@ -209,7 +209,8 @@ static void rec_stop(jit_State *J, TraceNo lnk)
 {
   lj_trace_end(J);
   J->cur.link = (uint16_t)lnk;
-  if (lnk == J->curtrace) {  /* Looping back? */
+  /* Looping back at the same stack level? */
+  if (lnk == J->curtrace && J->framedepth + J->retdepth == 0) {
     if ((J->flags & JIT_F_OPT_LOOP))  /* Shall we try to create a loop? */
       goto nocanon;  /* Do not canonicalize or we lose the narrowing. */
     if (J->cur.root)  /* Otherwise ensure we always link to the root trace. */
@@ -368,7 +369,7 @@ static int innerloopleft(jit_State *J, const BCIns *pc)
 static void rec_loop_interp(jit_State *J, const BCIns *pc, LoopEvent ev)
 {
   if (J->parent == 0) {
-    if (pc == J->startpc && J->framedepth == 0 && !J->chain[IR_RETF]) {
+    if (pc == J->startpc && J->framedepth + J->retdepth == 0) {
       /* Same loop? */
       if (ev == LOOPEV_LEAVE)  /* Must loop back to form a root trace. */
 	lj_trace_err(J, LJ_TRERR_LLEAVE);
@@ -401,7 +402,7 @@ static void rec_loop_jit(jit_State *J, TraceNo lnk, LoopEvent ev)
     lj_trace_err(J, LJ_TRERR_LINNER);
   } else if (ev != LOOPEV_LEAVE) {  /* Side trace enters a compiled loop. */
     J->instunroll = 0;  /* Cannot continue across a compiled loop op. */
-    if (J->pc == J->startpc && J->framedepth == 0 && !J->chain[IR_RETF])
+    if (J->pc == J->startpc && J->framedepth + J->retdepth == 0)
       lnk = J->curtrace;  /* Can form an extra loop. */
     rec_stop(J, lnk);  /* Link to the loop. */
   }  /* Side trace continues across a loop that's left or not entered. */
@@ -1538,6 +1539,7 @@ static void rec_ret(jit_State *J, BCReg rbase, ptrdiff_t gotresults)
       TRef trpt = lj_ir_kgc(J, obj2gco(pt), IRT_PROTO);
       TRef trpc = lj_ir_kptr(J, (void *)frame_pc(frame));
       emitir(IRTG(IR_RETF, IRT_PTR), trpt, trpc);
+      J->retdepth++;
       J->needsnap = 1;
       lua_assert(J->baseslot == 1);
       /* Shift result slots up and clear the slots of the new frame below. */
@@ -1584,8 +1586,9 @@ static void check_call_unroll(jit_State *J, GCfunc *fn)
       frame = frame_prevd(frame);
     frame = frame_prev(frame);
   }
-  if (frame_func(first) == fn && bc_op(J->cur.startins) == BC_CALL) {
-    if (count >= J->param[JIT_P_recunroll])
+  if (bc_op(J->cur.startins) == BC_CALL &&
+      funcproto(fn) == &gcref(J->cur.startpt)->pt) {
+    if (count + J->tailcalled >= J->param[JIT_P_recunroll])
       lj_trace_err(J, LJ_TRERR_NYIRECU);
   } else {
     if (count >= J->param[JIT_P_callunroll])
@@ -2236,6 +2239,7 @@ void lj_record_setup(jit_State *J)
   J->base = J->slot + J->baseslot;
   J->maxslot = 0;
   J->framedepth = 0;
+  J->retdepth = 0;
 
   J->instunroll = J->param[JIT_P_instunroll];
   J->loopunroll = J->param[JIT_P_loopunroll];
diff --git a/src/lj_trace.c b/src/lj_trace.c
index d1883ad2..ce313df3 100644
--- a/src/lj_trace.c
+++ b/src/lj_trace.c
@@ -491,7 +491,8 @@ static TValue *trace_state(lua_State *L, lua_CFunction dummy, void *ud)
 
     case LJ_TRACE_END:
       J->loopref = 0;
-      if ((J->flags & JIT_F_OPT_LOOP) && J->cur.link == J->curtrace) {
+      if ((J->flags & JIT_F_OPT_LOOP) &&
+	  J->cur.link == J->curtrace && J->framedepth + J->retdepth == 0) {
 	setvmstate(J2G(J), OPT);
 	lj_opt_dce(J);
 	if (lj_opt_loop(J)) {  /* Loop optimization failed? */