diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a6de7461d90..b666c83777d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2004-09-14  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
+
+	* tree-cfg.c (thread_jumps): Update dominators correctly in
+	case destination of threaded edge dominates its source.
+
 2004-09-14  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
 
 	* unroll.c: Removed.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4e59e16fbcb..02953de7b63 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2004-09-14  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
+
+	* gcc.c-torture/compile/20040914-1.c: New test.
+
 2004-09-13  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/16162
diff --git a/gcc/testsuite/gcc.c-torture/compile/20040914-1.c b/gcc/testsuite/gcc.c-torture/compile/20040914-1.c
new file mode 100644
index 00000000000..824664c889b
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/20040914-1.c
@@ -0,0 +1,39 @@
+extern int clobber_k (int *); 
+extern int barrier (void); 
+int t, u; 
+
+int
+process_second_stream(void) 
+{ 
+  int k; 
+  int i = 0, j = 0, result; 
+ 
+  clobber_k (&k); 
+ 
+  while(t)
+    ;
+ 
+  while(!j) 
+    {
+      while(!j) 
+	{ 
+	  barrier (); 
+	  if (t == 0) 
+	    break; 
+	  else if(t == 1) 
+	    t = 2; 
+	  else 
+	    {
+	      if(t < 0) 
+		j=1; 
+	      if(u < 0) 
+		k = i++; 
+	    }
+	} 
+ 
+      if(!j && u) 
+	j=1; 
+    } 
+ 
+  return 0; 
+} 
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 8e9e5af64ac..6f21467ca10 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -3970,9 +3970,11 @@ thread_jumps (void)
 		set_immediate_dominator (CDI_DOMINATORS, old_dest, bb);
 
 	      /* Now proceed like if we forwarded just over one edge at a time.
-		 Algorithm for forwarding over edge A --> B then is
+		 Algorithm for forwarding edge S --> A over edge A --> B then
+		 is
 
-		 if (idom (B) == A)
+		 if (idom (B) == A
+		     && !dominated_by (S, B))
 		   idom (B) = idom (A);
 		 recount_idom (A);  */
 
@@ -3980,7 +3982,8 @@ thread_jumps (void)
 		{
 		  tmp = old_dest->succ->dest;
 
-		  if (get_immediate_dominator (CDI_DOMINATORS, tmp) == old_dest)
+		  if (get_immediate_dominator (CDI_DOMINATORS, tmp) == old_dest
+		      && !dominated_by_p (CDI_DOMINATORS, bb, tmp))
 		    {
 		      dom = get_immediate_dominator (CDI_DOMINATORS, old_dest);
   		      set_immediate_dominator (CDI_DOMINATORS, tmp, dom);