gcc/ChangeLog:

PR tree-optimization/20640
* tree-ssa-dce.c (remove_dead_stmt): Don't redirect edge to
post-dominator if it has phi nodes.
(eliminate_unnecessary_stmts): Remove dead phis in all blocks
before dead statements.
gcc/testsuite/ChangeLog:
PR tree-optimization/20640
* gcc.dg/torture/tree-loop-1.c: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@97446 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d03fcf9..3cb960e 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,13 @@
 2005-04-02  Alexandre Oliva  <aoliva@redhat.com>
 
+       PR tree-optimization/20640
+       * tree-ssa-dce.c (remove_dead_stmt): Don't redirect edge to
+       post-dominator if it has phi nodes.
+       (eliminate_unnecessary_stmts): Remove dead phis in all blocks
+       before dead statements.
+
+2005-04-02  Alexandre Oliva  <aoliva@redhat.com>
+
        PR middle-end/20491
        * final.c (alter_subreg): Don't call subreg_regno for a non-REG.
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c2a4928..1264cf7 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2005-04-02  Alexandre Oliva  <aoliva@redhat.com>
 
+       PR tree-optimization/20640
+       * gcc.dg/torture/tree-loop-1.c: New.
+
+2005-04-02  Alexandre Oliva  <aoliva@redhat.com>
+
        PR rtl-optimization/20290
        * gcc.c-torture/execute/loop-ivopts-2.c: New.
 

diff --git a/gcc/testsuite/gcc.dg/torture/tree-loop-1.c b/gcc/testsuite/gcc.dg/torture/tree-loop-1.c
new file mode 100644 (file)
index 0000000..1d38691
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/tree-loop-1.c
@@ -0,0 +1,21 @@
+/* PR tree-optimization/20640 */
+
+/* After unrolling the loop, we'd turn some conditional branches into
+   unconditional ones, but branch redirection would fail to compute
+   the PHI args for the PHI nodes in the replacement edge
+   destination, so they'd remain NULL causing crashes later on.  */
+
+/* { dg-do compile } */
+
+static int a = 0;
+extern int foo (void);
+extern int *bar (void) __attribute__ ((__const__));
+
+void
+test (int x)
+{
+  int b = 10;
+  while (foo () == -1 && *bar () == 4 && b > 0)
+    --b;
+  a = x;
+}

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index f8946bc..dc388ee 100644 (file)
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -637,7 +637,10 @@ eliminate_unnecessary_stmts (void)
     {
       /* Remove dead PHI nodes.  */
       remove_dead_phis (bb);
+    }
 
+  FOR_EACH_BB (bb)
+    {
       /* Remove dead statements.  */
       for (i = bsi_start (bb); ! bsi_end_p (i) ; )
        {
@@ -724,6 +727,7 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
   if (is_ctrl_stmt (t))
     {
       basic_block post_dom_bb;
+
       /* The post dominance info has to be up-to-date.  */
       gcc_assert (dom_computed[CDI_POST_DOMINATORS] == DOM_OK);
       /* Get the immediate post dominator of bb.  */
@@ -737,9 +741,20 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
          return;
        }
 
-      /* Redirect the first edge out of BB to reach POST_DOM_BB.  */
-      redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb);
-      PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL;
+      /* If the post dominator block has PHI nodes, we might be unable
+        to compute the right PHI args for them.  Since the control
+        statement is unnecessary, all edges can be regarded as
+        equivalent, but we have to get rid of the condition, since it
+        might reference a variable that was determined to be
+        unnecessary and thus removed.  */
+      if (phi_nodes (post_dom_bb))
+       post_dom_bb = EDGE_SUCC (bb, 0)->dest;
+      else
+       {
+         /* Redirect the first edge out of BB to reach POST_DOM_BB.  */
+         redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb);
+         PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL;
+       }
       EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
       EDGE_SUCC (bb, 0)->count = bb->count;