tree-optimization/102659 - really avoid undef overflow in if-conversion

This plugs the remaining hole of POINTER_PLUS_EXPR with undefined
overflow.  Unfortunately we have to go through some lengths to
not put invariant conversions into the loop body since that confuses
the vectorizers gather/scatter discovery which relies on identifying
an invariant component of plus and minus expressions.  We can
emit those in the loop preheader but then we have to accept that
being non-empty when looking for the LOOP_VECTORIZED internal
function call in the vectorizer.

2021-10-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102659
	* tree-if-conv.c (if_convertible_gimple_assign_stmt_p): Also
	rewrite pointer typed undefined overflow operations.
	(predicate_statements): Likewise.  Make sure to emit invariant
	conversions in the preheader.
	* tree-vectorizer.c (vect_loop_vectorized_call): Look through
	non-empty preheaders.
	* tree-data-ref.c (dr_analyze_indices): Strip useless
	conversions to the MEM_REF base type.

3 files changed, 33 insertions, 8 deletions

diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index 18307a5..57bac06 100644
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -1370,6 +1370,7 @@ dr_analyze_indices (struct indices *dri, tree ref, edge nest, loop_p loop)
       tree op = TREE_OPERAND (ref, 0);
       tree access_fn = analyze_scalar_evolution (loop, op);
       access_fn = instantiate_scev (nest, loop, access_fn);
+      STRIP_NOPS (access_fn);
       if (TREE_CODE (access_fn) == POLYNOMIAL_CHREC)
 	{
 	  tree memoff = TREE_OPERAND (ref, 1);
diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index 0b6b07c..15dcc1e 100644
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -1047,7 +1047,8 @@ if_convertible_gimple_assign_stmt_p (gimple *stmt,
 	fprintf (dump_file, "tree could trap...\n");
       return false;
     }
-  else if (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+  else if ((INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+	    || POINTER_TYPE_P (TREE_TYPE (lhs)))
 	   && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (lhs))
 	   && arith_code_with_undefined_signed_overflow
 				(gimple_assign_rhs_code (stmt)))
@@ -2520,6 +2521,7 @@ predicate_statements (loop_p loop)
       for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
 	{
 	  gassign *stmt = dyn_cast <gassign *> (gsi_stmt (gsi));
+	  tree lhs;
 	  if (!stmt)
 	    ;
 	  else if (is_false_predicate (cond)
@@ -2574,15 +2576,36 @@ predicate_statements (loop_p loop)
 
 	      gsi_replace (&gsi, new_stmt, true);
 	    }
-	  else if (INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_lhs (stmt)))
-		   && TYPE_OVERFLOW_UNDEFINED
-			(TREE_TYPE (gimple_assign_lhs (stmt)))
+	  else if (((lhs = gimple_assign_lhs (stmt)), true)
+		   && (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+		       || POINTER_TYPE_P (TREE_TYPE (lhs)))
+		   && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (lhs))
 		   && arith_code_with_undefined_signed_overflow
 						(gimple_assign_rhs_code (stmt)))
 	    {
 	      gsi_remove (&gsi, true);
-	      gsi_insert_seq_before (&gsi, rewrite_to_defined_overflow (stmt),
-				     GSI_LAST_NEW_STMT);
+	      gimple_seq stmts = rewrite_to_defined_overflow (stmt);
+	      bool first = true;
+	      for (gimple_stmt_iterator gsi2 = gsi_start (stmts);
+		   !gsi_end_p (gsi2);)
+		{
+		  gassign *stmt2 = as_a <gassign *> (gsi_stmt (gsi2));
+		  gsi_remove (&gsi2, false);
+		  /* Make sure to move invariant conversions out of the
+		     loop.  */
+		  if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt2))
+		      && expr_invariant_in_loop_p (loop,
+						   gimple_assign_rhs1 (stmt2)))
+		    gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
+						  stmt2);
+		  else if (first)
+		    {
+		      gsi_insert_before (&gsi, stmt2, GSI_NEW_STMT);
+		      first = false;
+		    }
+		  else
+		    gsi_insert_after (&gsi, stmt2, GSI_NEW_STMT);
+		}
 	    }
 	  else if (gimple_vdef (stmt))
 	    {
@@ -2601,7 +2624,7 @@ predicate_statements (loop_p loop)
 	      gimple_assign_set_rhs1 (stmt, ifc_temp_var (type, rhs, &gsi));
 	      update_stmt (stmt);
 	    }
-	  tree lhs = gimple_get_lhs (gsi_stmt (gsi));
+	  lhs = gimple_get_lhs (gsi_stmt (gsi));
 	  if (lhs && TREE_CODE (lhs) == SSA_NAME)
 	    ssa_names.add (lhs);
 	  gsi_next (&gsi);
diff --git a/gcc/tree-vectorizer.c b/gcc/tree-vectorizer.c
index 20daa31..4712dc6 100644
--- a/gcc/tree-vectorizer.c
+++ b/gcc/tree-vectorizer.c
@@ -852,7 +852,8 @@ vect_loop_vectorized_call (class loop *loop, gcond **cond)
   do
     {
       g = last_stmt (bb);
-      if (g)
+      if ((g && gimple_code (g) == GIMPLE_COND)
+	  || !single_succ_p (bb))
 	break;
       if (!single_pred_p (bb))
 	break;