diff options
| author | Richard Guenther <rguenther@suse.de> | 2009-06-30 15:23:39 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2009-06-30 15:23:39 +0000 |
| commit | 67635176a2a643036f86c55cba8bcf79f56821a5 (patch) | |
| tree | a545660a88ba18ccce1692e097184bf0f4994b56 /gcc/tree-ssa-dce.c | |
| parent | ca89096d931f77c58dc19bce88e2a2eff04df6da (diff) | |
| download | gcc-67635176a2a643036f86c55cba8bcf79f56821a5.tar.gz | |
tree-ssa-dce.c (mark_all_reaching_defs_necessary_1): Always continue walking.
2009-06-30 Richard Guenther <rguenther@suse.de>
* tree-ssa-dce.c (mark_all_reaching_defs_necessary_1): Always
continue walking.
(propagate_necessity): Do not mark reaching defs of stores
as necessary.
* gcc.dg/tree-ssa/ssa-dce-6.c: New testcase.
From-SVN: r149103
Diffstat (limited to 'gcc/tree-ssa-dce.c')
| -rw-r--r-- | gcc/tree-ssa-dce.c | 22 |
1 files changed, 7 insertions, 15 deletions
diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c index 0cb8ac6afd8..8522c5c5797 100644 --- a/gcc/tree-ssa-dce.c +++ b/gcc/tree-ssa-dce.c @@ -550,9 +550,9 @@ mark_all_reaching_defs_necessary_1 (ao_ref *ref ATTRIBUTE_UNUSED, return false; } - /* But can stop after the first necessary statement. */ mark_operand_necessary (vdef); - return true; + + return false; } static void @@ -671,18 +671,15 @@ propagate_necessity (struct edge_list *el) For 1) we mark all reaching may-defs as necessary, stopping at dominating kills. For 2) we want to mark all dominating references necessary, but non-aliased ones which we handle - in 1). Instead of doing so for each load we rely on the - worklist to eventually reach all dominating references and - instead just mark the immediately dominating references - as necessary (but skipping non-aliased ones). */ + in 1). By keeping a global visited bitmap for references + we walk for 2) we avoid quadratic behavior for those. */ if (is_gimple_call (stmt)) { unsigned i; /* Calls implicitly load from memory, their arguments - in addition may explicitly perform memory loads. - This also ensures propagation for case 2 for stores. */ + in addition may explicitly perform memory loads. */ mark_all_reaching_defs_necessary (stmt); for (i = 0; i < gimple_call_num_args (stmt); ++i) { @@ -696,7 +693,7 @@ propagate_necessity (struct edge_list *el) } else if (gimple_assign_single_p (stmt)) { - tree lhs, rhs; + tree rhs; bool rhs_aliased = false; /* If this is a load mark things necessary. */ rhs = gimple_assign_rhs1 (stmt); @@ -708,12 +705,7 @@ propagate_necessity (struct edge_list *el) else rhs_aliased = true; } - /* If this is an aliased store, mark things necessary. - This is where we make sure to propagate for case 2. */ - lhs = gimple_assign_lhs (stmt); - if (rhs_aliased - || (TREE_CODE (lhs) != SSA_NAME - && ref_may_be_aliased (lhs))) + if (rhs_aliased) mark_all_reaching_defs_necessary (stmt); } else if (gimple_code (stmt) == GIMPLE_RETURN) |