tree-optimization/93946 - fix bogus redundant store removal in FRE, DSE and DOM

This fixes a common mistake in removing a store that looks redudnant but
is not because it changes the dynamic type of the memory and thus makes
a difference for following loads with TBAA.

2020-03-03  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/93946
	* alias.h (refs_same_for_tbaa_p): Declare.
	* alias.c (refs_same_for_tbaa_p): New function.
	* tree-ssa-alias.c (ao_ref_alias_set): For a NULL ref return
	zero.
	* tree-ssa-scopedtables.h
	(avail_exprs_stack::lookup_avail_expr): Add output argument
	giving access to the hashtable entry.
	* tree-ssa-scopedtables.c (avail_exprs_stack::lookup_avail_expr):
	Likewise.
	* tree-ssa-dom.c: Include alias.h.
	(dom_opt_dom_walker::optimize_stmt): Validate TBAA state before
	removing redundant store.
	* tree-ssa-sccvn.h (vn_reference_s::base_set): New member.
	(ao_ref_init_from_vn_reference): Adjust prototype.
	(vn_reference_lookup_pieces): Likewise.
	(vn_reference_insert_pieces): Likewise.
	* tree-ssa-sccvn.c: Track base alias set in addition to alias
	set everywhere.
	(eliminate_dom_walker::eliminate_stmt): Also check base alias
	set when removing redundant stores.
	(visit_reference_op_store): Likewise.
	* dse.c (record_store): Adjust valdity check for redundant
	store removal.

	* gcc.dg/torture/pr93946-1.c: New testcase.
	* gcc.dg/torture/pr93946-2.c: Likewise.

1 files changed, 16 insertions, 8 deletions

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index eaed4b16ed8..29987d840fd 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -1140,7 +1140,8 @@ fully_constant_expression (pre_expr e)
 
 static tree
 translate_vuse_through_block (vec<vn_reference_op_s> operands,
-			      alias_set_type set, tree type, tree vuse,
+			      alias_set_type set, alias_set_type base_set,
+			      tree type, tree vuse,
 			      basic_block phiblock,
 			      basic_block block, bool *same_valid)
 {
@@ -1156,7 +1157,8 @@ translate_vuse_through_block (vec<vn_reference_op_s> operands,
     return vuse;
 
   unsigned int cnt = param_sccvn_max_alias_queries_per_access;
-  use_oracle = ao_ref_init_from_vn_reference (&ref, set, type, operands);
+  use_oracle = ao_ref_init_from_vn_reference (&ref, set, base_set,
+					      type, operands);
 
   /* Use the alias-oracle to find either the PHI node in this block,
      the first VUSE used in this block that is equivalent to vuse or
@@ -1535,7 +1537,8 @@ phi_translate_1 (bitmap_set_t dest,
 	  {
 	    newvuse = translate_vuse_through_block (newoperands.exists ()
 						    ? newoperands : operands,
-						    ref->set, ref->type,
+						    ref->set, ref->base_set,
+						    ref->type,
 						    vuse, phiblock, pred,
 						    changed
 						    ? NULL : &same_valid);
@@ -1551,6 +1554,7 @@ phi_translate_1 (bitmap_set_t dest,
 	    unsigned int new_val_id;
 
 	    tree result = vn_reference_lookup_pieces (newvuse, ref->set,
+						      ref->base_set,
 						      ref->type,
 						      newoperands.exists ()
 						      ? newoperands : operands,
@@ -1608,7 +1612,7 @@ phi_translate_1 (bitmap_set_t dest,
 		if (!newoperands.exists ())
 		  newoperands = operands.copy ();
 		newref = vn_reference_insert_pieces (newvuse, ref->set,
-						     ref->type,
+						     ref->base_set, ref->type,
 						     newoperands,
 						     result, new_val_id);
 		newoperands = vNULL;
@@ -1827,8 +1831,8 @@ value_dies_in_block_x (pre_expr expr, basic_block block)
 
       /* Init ref only if we really need it.  */
       if (ref.base == NULL_TREE
-	  && !ao_ref_init_from_vn_reference (&ref, refx->set, refx->type,
-					     refx->operands))
+	  && !ao_ref_init_from_vn_reference (&ref, refx->set, refx->base_set,
+					     refx->type, refx->operands))
 	{
 	  res = true;
 	  break;
@@ -3914,12 +3918,16 @@ compute_avail (void)
 		  case VN_REFERENCE:
 		    {
 		      tree rhs1 = gimple_assign_rhs1 (stmt);
-		      alias_set_type set = get_alias_set (rhs1);
+		      ao_ref rhs1_ref;
+		      ao_ref_init (&rhs1_ref, rhs1);
+		      alias_set_type set = ao_ref_alias_set (&rhs1_ref);
+		      alias_set_type base_set
+			= ao_ref_base_alias_set (&rhs1_ref);
 		      vec<vn_reference_op_s> operands
 			= vn_reference_operands_for_lookup (rhs1);
 		      vn_reference_t ref;
 		      vn_reference_lookup_pieces (gimple_vuse (stmt), set,
-						  TREE_TYPE (rhs1),
+						  base_set, TREE_TYPE (rhs1),
 						  operands, &ref, VN_WALK);
 		      if (!ref)
 			{