2005-03-01 Daniel Berlin <dberlin@dberlin.org>

	* Makefile.in (tree-ssa-sink.o): New.
	(OBJS-common): Add tree-ssa-sink.o.
	* common.opt: Add -ftree-sink
	* opts.c (decode_options): flag_tree_sink is set at O1 or higher.
	* timevar.def (TV_TREE_SINK): new timevar.
	* tree-flow.h (is_hidden_global_store): Prototype.
	* tree-optimize.c (init_tree_optimization_passes): Add
	pass_sink_code.
	* tree-pass.h (pass_sink_code): New.
	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Move checking
	for non-obvious global store store to is_hidden_global_store, and
	call that new function.
	* tree-ssa-sink.c: New file.
	* doc/invoke.texi: Document -fdump-tree-sink and -ftree-sink.
	* doc/passes.texi: Document forward store motion.
	* testsuite/gcc.dg/tree-ssa/ssa-sink-1.c: New test
	* testsuite/gcc.dg/tree-ssa/ssa-sink-2.c: New test
	* testsuite/gcc.dg/tree-ssa/ssa-sink-3.c: New test
	* testsuite/gcc.dg/tree-ssa/ssa-sink-4.c: New test


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@95750 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 3 insertions, 73 deletions

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 16b9d480a49..69408e8cd7d 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -277,8 +277,6 @@ mark_operand_necessary (tree op, bool phionly)
 static void
 mark_stmt_if_obviously_necessary (tree stmt, bool aggressive)
 {
-  v_may_def_optype v_may_defs;
-  v_must_def_optype v_must_defs;
   stmt_ann_t ann;
   tree op, def;
   ssa_op_iter iter;
@@ -368,78 +366,10 @@ mark_stmt_if_obviously_necessary (tree stmt, bool aggressive)
 	  return;
         }
     }
-
-  /* Check virtual definitions.  If we get here, the only virtual
-     definitions we should see are those generated by assignment
-     statements.  */
-  v_may_defs = V_MAY_DEF_OPS (ann);
-  v_must_defs = V_MUST_DEF_OPS (ann);
-  if (NUM_V_MAY_DEFS (v_may_defs) > 0 || NUM_V_MUST_DEFS (v_must_defs) > 0)
+  if (is_hidden_global_store (stmt))
     {
-      tree lhs;
-
-      gcc_assert (TREE_CODE (stmt) == MODIFY_EXPR);
-
-      /* Note that we must not check the individual virtual operands
-	 here.  In particular, if this is an aliased store, we could
-	 end up with something like the following (SSA notation
-	 redacted for brevity):
-
-	 	foo (int *p, int i)
-		{
-		  int x;
-		  p_1 = (i_2 > 3) ? &x : p_1;
-
-		  # x_4 = V_MAY_DEF <x_3>
-		  *p_1 = 5;
-
-		  return 2;
-		}
-
-	 Notice that the store to '*p_1' should be preserved, if we
-	 were to check the virtual definitions in that store, we would
-	 not mark it needed.  This is because 'x' is not a global
-	 variable.
-
-	 Therefore, we check the base address of the LHS.  If the
-	 address is a pointer, we check if its name tag or type tag is
-	 a global variable.  Otherwise, we check if the base variable
-	 is a global.  */
-      lhs = TREE_OPERAND (stmt, 0);
-      if (REFERENCE_CLASS_P (lhs))
-	lhs = get_base_address (lhs);
-
-      if (lhs == NULL_TREE)
-	{
-	  /* If LHS is NULL, it means that we couldn't get the base
-	     address of the reference.  In which case, we should not
-	     remove this store.  */
-	  mark_stmt_necessary (stmt, true);
-	}
-      else if (DECL_P (lhs))
-	{
-	  /* If the store is to a global symbol, we need to keep it.  */
-	  if (is_global_var (lhs))
-	    mark_stmt_necessary (stmt, true);
-	}
-      else if (INDIRECT_REF_P (lhs))
-	{
-	  tree ptr = TREE_OPERAND (lhs, 0);
-	  struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
-	  tree nmt = (pi) ? pi->name_mem_tag : NULL_TREE;
-	  tree tmt = var_ann (SSA_NAME_VAR (ptr))->type_mem_tag;
-
-	  /* If either the name tag or the type tag for PTR is a
-	     global variable, then the store is necessary.  */
-	  if ((nmt && is_global_var (nmt))
-	      || (tmt && is_global_var (tmt)))
-	    {
-	      mark_stmt_necessary (stmt, true);
-	      return;
-	    }
-	}
-      else
-	gcc_unreachable ();
+      mark_stmt_necessary (stmt, true);
+      return;
     }
 
   return;