2010-01-20 Richard Guenther <rguenther@suse.de>

	PR tree-optimization/42717
	* tree-ssa-dce.c (get_live_post_dom): Remove.
	(forward_edge_to_pdom): Take an arbitrary edge to copy
	degenerate PHI args from.
	(remove_dead_stmt): Use the first post-dominator even if it
	does not contain live statements as redirection destination.

	* gcc.c-torture/compile/pr42717.c: New testcase.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@156076 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 56c60ba..4a70dc7 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,14 @@
 2010-01-20  Richard Guenther  <rguenther@suse.de>
 
+       PR tree-optimization/42717
+       * tree-ssa-dce.c (get_live_post_dom): Remove.
+       (forward_edge_to_pdom): Take an arbitrary edge to copy
+       degenerate PHI args from.
+       (remove_dead_stmt): Use the first post-dominator even if it
+       does not contain live statements as redirection destination.
+
+2010-01-20  Richard Guenther  <rguenther@suse.de>
+
        * tree-inline.c (estimate_num_insns): Handle EH builtins.
 
 2010-01-20  Jakub Jelinek  <jakub@redhat.com>

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 476d0fd..6d7c3a6 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2010-01-20  Richard Guenther  <rguenther@suse.de>
+
+       PR tree-optimization/42717
+       * gcc.c-torture/compile/pr42717.c: New testcase.
+
 2010-01-20  Jakub Jelinek  <jakub@redhat.com>
 
        * gcc.dg/cleanup-13.c: Expect DW_OP_mod to do unsigned modulo instead

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr42717.c b/gcc/testsuite/gcc.c-torture/compile/pr42717.c
new file mode 100644 (file)
index 0000000..4fe6f93
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr42717.c
@@ -0,0 +1,30 @@
+static signed char
+foo (signed char si1, unsigned char si2)
+{
+  return (si1 ^ si2) & (-si2 ^ si2) ? : si1 - si2;
+}
+
+struct S0
+{
+};
+
+unsigned char g_21;
+
+struct S0 g_34;
+
+void
+bar (unsigned char p_20)
+{
+  unsigned char *l_22 = &g_21;
+  unsigned char l_23 = 0;
+  struct S0 *l = &g_34;
+  goto lbl_42;
+  for (; l_23; l_23 = foo (l_23, 1))
+    {
+      for (p_20 = 0; 0; p_20 = foo (p_20, 1))
+       lbl_42:;
+      (l == &g_34) ? 0 : "";
+lbl_85:*l_22 = p_20;
+    }
+  goto lbl_85;
+}

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index bb24b62..4e3499a 100644 (file)
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -917,27 +917,6 @@ remove_dead_phis (basic_block bb)
   return something_changed;
 }
 
-/* Find first live post dominator of BB.  */
-
-static basic_block
-get_live_post_dom (basic_block bb)
-{
-  basic_block post_dom_bb;
-
-
-  /* The post dominance info has to be up-to-date.  */
-  gcc_assert (dom_info_state (CDI_POST_DOMINATORS) == DOM_OK);
-
-  /* Get the immediate post dominator of bb.  */
-  post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
-  /* And look for first live one.  */
-  while (post_dom_bb != EXIT_BLOCK_PTR
-        && !TEST_BIT (bb_contains_live_stmts, post_dom_bb->index))
-    post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, post_dom_bb);
-
-  return post_dom_bb;
-}
-
 /* Forward edge E to respective POST_DOM_BB and update PHIs.  */
 
 static edge
@@ -961,10 +940,9 @@ forward_edge_to_pdom (edge e, basic_block post_dom_bb)
   if (!gimple_seq_empty_p (phi_nodes (post_dom_bb)))
     {
       /* We are sure that for every live PHI we are seeing control dependent BB.
-         This means that we can look up the end of control dependent path leading
-         to the PHI itself.  */
+         This means that we can pick any edge to duplicate PHI args from.  */
       FOR_EACH_EDGE (e2, ei, post_dom_bb->preds)
-       if (e2 != e && dominated_by_p (CDI_POST_DOMINATORS, e->src, e2->src))
+       if (e2 != e)
          break;
       for (gsi = gsi_start_phis (post_dom_bb); !gsi_end_p (gsi);)
        {
@@ -972,40 +950,27 @@ forward_edge_to_pdom (edge e, basic_block post_dom_bb)
          tree op;
          source_location locus;
 
-         /* Dead PHI do not imply control dependency.  */
-          if (!gimple_plf (phi, STMT_NECESSARY)
-             && is_gimple_reg (gimple_phi_result (phi)))
-           {
-             gsi_next (&gsi);
-             continue;
-           }
-         if (gimple_phi_arg_def (phi, e->dest_idx))
-           {
-             gsi_next (&gsi);
-             continue;
-           }
-
-         /* We didn't find edge to update.  This can happen for PHIs on virtuals
-            since there is no control dependency relation on them.  We are lost
-            here and must force renaming of the symbol.  */
+         /* PHIs for virtuals have no control dependency relation on them.
+            We are lost here and must force renaming of the symbol.  */
          if (!is_gimple_reg (gimple_phi_result (phi)))
            {
              mark_virtual_phi_result_for_renaming (phi);
              remove_phi_node (&gsi, true);
              continue;
            }
-         if (!e2)
-           {
-             op = gimple_phi_arg_def (phi, e->dest_idx == 0 ? 1 : 0);
-             locus = gimple_phi_arg_location (phi, e->dest_idx == 0 ? 1 : 0);
-           }
-         else
+
+         /* Dead PHI do not imply control dependency.  */
+          if (!gimple_plf (phi, STMT_NECESSARY))
            {
-             op = gimple_phi_arg_def (phi, e2->dest_idx);
-             locus = gimple_phi_arg_location (phi, e2->dest_idx);
+             gsi_next (&gsi);
+             continue;
            }
+
+         op = gimple_phi_arg_def (phi, e2->dest_idx);
+         locus = gimple_phi_arg_location (phi, e2->dest_idx);
          add_phi_arg (phi, op, e, locus);
-         gcc_assert (e2 || degenerate_phi_p (phi));
+         /* The resulting PHI if not dead can only be degenerate.  */
+         gcc_assert (degenerate_phi_p (phi));
          gsi_next (&gsi);
        }
     }
@@ -1041,7 +1006,7 @@ remove_dead_stmt (gimple_stmt_iterator *i, basic_block bb)
       edge e, e2;
       edge_iterator ei;
 
-      post_dom_bb = get_live_post_dom (bb);
+      post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
 
       e = find_edge (bb, post_dom_bb);