2014-10-10 Richard Biener <rguenther@suse.de>

	PR tree-optimization/63476
	* tree-ssa-pre.c (struct bb_bitmap_sets): Add vop_on_exit member.
	(BB_LIVE_VOP_ON_EXIT): New define.
	(create_expression_by_pieces): Assign VUSEs to stmts.
	(compute_avail): Track BB_LIVE_VOP_ON_EXIT.
	(pass_pre::execute): Assert virtual SSA form is up-to-date
	after insertion.

	* g++.dg/torture/pr63476.C: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@216065 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 25 insertions, 2 deletions

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index cbbd4220433..a447c1e4f06 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -423,6 +423,9 @@ typedef struct bb_bitmap_sets
   /* A cache for value_dies_in_block_x.  */
   bitmap expr_dies;
 
+  /* The live virtual operand on successor edges.  */
+  tree vop_on_exit;
+
   /* True if we have visited this block during ANTIC calculation.  */
   unsigned int visited : 1;
 
@@ -440,6 +443,7 @@ typedef struct bb_bitmap_sets
 #define EXPR_DIES(BB)	((bb_value_sets_t) ((BB)->aux))->expr_dies
 #define BB_VISITED(BB)	((bb_value_sets_t) ((BB)->aux))->visited
 #define BB_MAY_NOTRETURN(BB) ((bb_value_sets_t) ((BB)->aux))->contains_may_not_return_call
+#define BB_LIVE_VOP_ON_EXIT(BB) ((bb_value_sets_t) ((BB)->aux))->vop_on_exit
 
 
 /* Basic block list in postorder.  */
@@ -2886,12 +2890,15 @@ create_expression_by_pieces (basic_block block, pre_expr expr,
 	      bitmap_value_replace_in_set (NEW_SETS (block), nameexpr);
 	      bitmap_value_replace_in_set (AVAIL_OUT (block), nameexpr);
 	    }
+
+	  gimple_set_vuse (stmt, BB_LIVE_VOP_ON_EXIT (block));
 	}
       gimple_seq_add_seq (stmts, forced_stmts);
     }
 
   name = make_temp_ssa_name (exprtype, NULL, "pretmp");
   newstmt = gimple_build_assign (name, folded);
+  gimple_set_vuse (newstmt, BB_LIVE_VOP_ON_EXIT (block));
   gimple_set_plf (newstmt, NECESSARY, false);
 
   gimple_seq_add_stmt (stmts, newstmt);
@@ -3593,6 +3600,9 @@ compute_avail (void)
        son = next_dom_son (CDI_DOMINATORS, son))
     worklist[sp++] = son;
 
+  BB_LIVE_VOP_ON_EXIT (ENTRY_BLOCK_PTR_FOR_FN (cfun))
+    = ssa_default_def (cfun, gimple_vop (cfun));
+
   /* Loop until the worklist is empty.  */
   while (sp)
     {
@@ -3607,7 +3617,10 @@ compute_avail (void)
 	 its immediate dominator.  */
       dom = get_immediate_dominator (CDI_DOMINATORS, block);
       if (dom)
-	bitmap_set_copy (AVAIL_OUT (block), AVAIL_OUT (dom));
+	{
+	  bitmap_set_copy (AVAIL_OUT (block), AVAIL_OUT (dom));
+	  BB_LIVE_VOP_ON_EXIT (block) = BB_LIVE_VOP_ON_EXIT (dom);
+	}
 
       /* Generate values for PHI nodes.  */
       for (gsi = gsi_start_phis (block); !gsi_end_p (gsi); gsi_next (&gsi))
@@ -3617,7 +3630,10 @@ compute_avail (void)
 	  /* We have no need for virtual phis, as they don't represent
 	     actual computations.  */
 	  if (virtual_operand_p (result))
-	    continue;
+	    {
+	      BB_LIVE_VOP_ON_EXIT (block) = result;
+	      continue;
+	    }
 
 	  pre_expr e = get_or_alloc_expr_for_name (result);
 	  add_to_value (get_expr_value_id (e), e);
@@ -3661,6 +3677,9 @@ compute_avail (void)
 	      bitmap_value_insert_into_set (AVAIL_OUT (block), e);
 	    }
 
+	  if (gimple_vdef (stmt))
+	    BB_LIVE_VOP_ON_EXIT (block) = gimple_vdef (stmt);
+
 	  if (gimple_has_side_effects (stmt)
 	      || stmt_could_throw_p (stmt)
 	      || is_gimple_debug (stmt))
@@ -4758,6 +4777,10 @@ pass_pre::execute (function *fun)
   remove_fake_exit_edges ();
   gsi_commit_edge_inserts ();
 
+  /* Eliminate folds statements which might (should not...) end up
+     not keeping virtual operands up-to-date.  */
+  gcc_assert (!need_ssa_update_p (fun));
+
   /* Remove all the redundant expressions.  */
   todo |= eliminate (true);