*** empty log message ***

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@321 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/jump.c b/gcc/jump.c
index da006bb..6e0b5f1 100644 (file)
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -1199,6 +1199,17 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
             is not defined and the condition is tested by a separate compare
             insn.  This is because the code below assumes that the result
             of the compare dies in the following branch.  */
+
+         /* ??? This has to be turned off.  The problem is that the
+            unconditional jump might indirectly end up branching to the
+            label between TEMP1 and TEMP.  We can't detect this, in general,
+            since it may become a jump to there after further optimizations.
+            If that jump is done, it will be deleted, so we will retry
+            this optimization in the next pass, thus an infinite loop.
+
+            The present code prevents this by putting the jump after the
+            label, but this is not logically correct.  */
+#if 0
          else if (this_is_condjump
                   /* Safe to skip USE and CLOBBER insns here
                      since they will not be deleted.  */
@@ -1260,9 +1271,9 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
                    /* Get the label out of the LABEL_REF.  */
                    ultimate = XEXP (ultimate, 0);
 
-                 /* Insert the jump after any USE or CLOBBER
-                    that follows TEMP1.  */
-                 last_insn = prev_real_insn (temp);
+                 /* Insert the jump immediately before TEMP, specifically
+                    after the label that is between TEMP1 and TEMP.  */
+                 last_insn = PREV_INSN (temp);
 
                  /* If we would be branching to the next insn, the jump
                     would immediately be deleted and the re-inserted in
@@ -1288,6 +1299,7 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
                    }
                }
            }
+#endif
          /* Detect a conditional jump going to the same place
             as an immediately following unconditional jump.  */
          else if (this_is_condjump
@@ -2513,6 +2525,8 @@ sets_cc0_p (x)
 /* Follow any unconditional jump at LABEL;
    return the ultimate label reached by any such chain of jumps.
    If LABEL is not followed by a jump, return LABEL.
+   If the chain loops or we can't find end, return LABEL,
+   since that tells caller to avoid changing the insn.
 
    If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
    a USE or CLOBBER.  */
@@ -2548,9 +2562,11 @@ follow_jumps (label)
 
       /* If we have found a cycle, make the insn jump to itself.  */
       if (JUMP_LABEL (insn) == label)
-       break;
+       return label;
       value = JUMP_LABEL (insn);
     }
+  if (depth == 10)
+    return label;
   return value;
 }
 
@@ -3098,7 +3114,8 @@ redirect_jump (jump, nlabel)
       int label_index = nlabel ? INSN_UID (nlabel) : 0;
 
       delete_from_jump_chain (jump);
-      if (label_index < max_jump_chain)
+      if (label_index < max_jump_chain
+         && INSN_UID (jump) < max_jump_chain)
        {
          jump_chain[INSN_UID (jump)] = jump_chain[label_index];
          jump_chain[label_index] = jump;