(find_basic_blocks): Ensure each live basic block is actually reachable.

(life_analysis): Clean up handling of basic_block_drops_in.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@8340 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/flow.c b/gcc/flow.c
index 76ef544..b0245f8 100644 (file)
--- a/gcc/flow.c
+++ b/gcc/flow.c
@@ -608,6 +608,20 @@ find_basic_blocks (f, nonlocal_label_list)
              }
        }
 
+      /* ??? See if we have a "live" basic block that is not reachable.
+        This can happen if it is headed by a label that is preserved or
+        in one of the label lists, but no call or computed jump is in
+        the loop.  It's not clear if we can delete the block or not,
+        but don't for now.  However, we will mess up register status if
+        it remains unreachable, so add a fake reachability from the
+        previous block.  */
+
+      for (i = 1; i < n_basic_blocks; i++)
+       if (block_live[i] && ! basic_block_drops_in[i]
+           && GET_CODE (basic_block_head[i]) == CODE_LABEL
+           && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
+         basic_block_drops_in[i] = 1;
+
       /* Now delete the code for any basic blocks that can't be reached.
         They can occur because jump_optimize does not recognize
         unreachable loops as unreachable.  */
@@ -1061,18 +1075,18 @@ life_analysis (f, nregs)
 
          {
            register rtx jump, head;
+
            /* Update the basic_block_new_live_at_end's of the block
               that falls through into this one (if any).  */
            head = basic_block_head[i];
-           jump = PREV_INSN (head);
            if (basic_block_drops_in[i])
              {
-               register int from_block = BLOCK_NUM (jump);
                register int j;
                for (j = 0; j < regset_size; j++)
-                 basic_block_new_live_at_end[from_block][j]
+                 basic_block_new_live_at_end[i-1][j]
                    |= basic_block_live_at_start[i][j];
              }
+
            /* Update the basic_block_new_live_at_end's of
               all the blocks that jump to this one.  */
            if (GET_CODE (head) == CODE_LABEL)