tree-ssa-propagate.c (substitute_and_fold): Substitute statements in a basic-block...

2008-04-15  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-propagate.c (substitute_and_fold): Substitute
	statements in a basic-block with a backward walk.  Do not
	substitute into dead statements but instead remove those.

	* gcc.dg/fold-compare-2.c: Adjust testcase.
	* gcc.dg/tree-ssa/pr21086.c: Likewise.

From-SVN: r134322

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f2bf992b1d8f9687362ccbf4d0993baf9dc2affb..9733411e8431eb854607a9db1c70cc011f0d60f1 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2008-04-15  Richard Guenther  <rguenther@suse.de>
+
+       * tree-ssa-propagate.c (substitute_and_fold): Substitute
+       statements in a basic-block with a backward walk.  Do not
+       substitute into dead statements but instead remove those.
+
 2008-04-15  Richard Guenther  <rguenther@suse.de>
 
        * params.def (PARAM_MAX_FIELDS_FOR_FIELD_SENSITIVE): Set default

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index aa9fe4770a56db722939e2cd2413ac41838e9cfb..64e45319fc2d59b50f3f3db7d68074bcd6fc8484 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2008-04-15  Richard Guenther  <rguenther@suse.de>
+
+       * gcc.dg/fold-compare-2.c: Adjust testcase.
+       * gcc.dg/tree-ssa/pr21086.c: Likewise.
+
 2008-04-15  Richard Guenther  <rguenther@suse.de>
 
        * gcc.dg/tree-ssa/salias-1.c: Remove.

diff --git a/gcc/testsuite/gcc.dg/fold-compare-2.c b/gcc/testsuite/gcc.dg/fold-compare-2.c
index bcdb7ad3fcbe58eee222797fa652972fb3b38557..6674c4dad6e32b9add31076854c8b18214f70eb4 100644 (file)
--- a/gcc/testsuite/gcc.dg/fold-compare-2.c
+++ b/gcc/testsuite/gcc.dg/fold-compare-2.c
@@ -15,6 +15,6 @@ main(void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
+/* { dg-final { scan-tree-dump-times "Removing basic block" 2 "vrp1" } } */
 /* { dg-final { cleanup-tree-dump "vrp\[1-2\]" } } */
 

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr21086.c b/gcc/testsuite/gcc.dg/tree-ssa/pr21086.c
index 1498ad75d25a5deee453000d4a8b41492c577b88..ffaccefe94c88c0136a36159a85eb8e0d956f278 100644 (file)
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr21086.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr21086.c
@@ -15,5 +15,6 @@ foo (int *p)
     return 0;
 }
 
-/* { dg-final { scan-tree-dump-times "Folding predicate " 2 "vrp1" } } */
+/* { dg-final { scan-tree-dump-times "Folding predicate " 1 "vrp1" } } */
+/* { dg-final { scan-tree-dump-not "b_. =" "vrp1" } } */
 /* { dg-final { cleanup-tree-dump "vrp1" } } */

diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index 98847fb377a05577c7c7c37c5334fdff59fcb9a6..c37cfa53545b07a2523c9c5ff2f8f4a6c29d8c5b 100644 (file)
--- a/gcc/tree-ssa-propagate.c
+++ b/gcc/tree-ssa-propagate.c
@@ -1211,10 +1211,12 @@ substitute_and_fold (prop_value_t *prop_value, bool use_ranges_p)
        for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
          replace_phi_args_in (phi, prop_value);
 
-      for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
+      /* Propagate known values into stmts.  Do a backward walk to expose
+        more trivially deletable stmts.  */
+      for (i = bsi_last (bb); !bsi_end_p (i);)
        {
           bool replaced_address, did_replace;
-         tree prev_stmt = NULL;
+         tree call, prev_stmt = NULL;
          tree stmt = bsi_stmt (i);
 
          /* Ignore ASSERT_EXPRs.  They are used by VRP to generate
@@ -1222,7 +1224,33 @@ substitute_and_fold (prop_value_t *prop_value, bool use_ranges_p)
             afterwards.  */
          if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
              && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ASSERT_EXPR)
-           continue;
+           {
+             bsi_prev (&i);
+             continue;
+           }
+
+         /* No point propagating into a stmt whose result is not used,
+            but instead we might be able to remove a trivially dead stmt.  */
+         if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+             && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 0)) == SSA_NAME
+             && !stmt_ann (stmt)->has_volatile_ops
+             && has_zero_uses (GIMPLE_STMT_OPERAND (stmt, 0))
+             && !tree_could_throw_p (stmt)
+             && (!(call = get_call_expr_in (stmt))
+                 || !TREE_SIDE_EFFECTS (call)))
+           {
+             if (dump_file && dump_flags & TDF_DETAILS)
+               {
+                 fprintf (dump_file, "Removing dead stmt ");
+                 print_generic_expr (dump_file, stmt, 0);
+                 fprintf (dump_file, "\n");
+               }
+             bsi_remove (&i, true);
+             release_defs (stmt);
+             if (!bsi_end_p (i))
+               bsi_prev (&i);
+             continue;
+           }
 
          /* Record the state of the statement before replacements.  */
          push_stmt_changes (bsi_stmt_ptr (i));
@@ -1298,6 +1326,8 @@ substitute_and_fold (prop_value_t *prop_value, bool use_ranges_p)
             statement.  */
          if (use_ranges_p)
            simplify_stmt_using_ranges (stmt);
+
+         bsi_prev (&i);
        }
     }