re PR tree-optimization/91178 (Infinite recursion in split_constant_offset in slp after r260289)

2019-07-31  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91178
	* tree-ssa-sccvn.c (vn_reference_maybe_forwprop_address):
	Use tail-recursion.

	* gcc.dg/torture/pr91178-2.c: New testcase.

From-SVN: r273928

gcc/ChangeLog

+2019-07-31  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/91178
+	* tree-ssa-sccvn.c (vn_reference_maybe_forwprop_address):
+	Use tail-recursion.
+
 2019-07-31  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/91201

gcc/testsuite/ChangeLog

+2019-07-31  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/91178
+	* gcc.dg/torture/pr91178-2.c: New testcase.
+
 2019-07-31  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/91201

gcc/testsuite/gcc.dg/torture/pr91178-2.c

+/* { dg-do compile } */
+
+int a[100][70304];
+int b[100];
+void c()
+{
+  for (int d = 2; d < 4; d++)
+    for (int e = 2; e <= 50; e++)
+      for (int f = 32; f <= 38; f++)
+	b[d + f] -= a[e][5];
+}

gcc/tree-ssa-sccvn.c

@@ -1249,8 +1249,13 @@ static bool
 vn_reference_maybe_forwprop_address (vec<vn_reference_op_s> *ops,
 				     unsigned int *i_p)
 {
+  bool changed = false;
+  vn_reference_op_t op;
+
+  do
+    {
       unsigned int i = *i_p;
-  vn_reference_op_t op = &(*ops)[i];
+      op = &(*ops)[i];
       vn_reference_op_t mem_op = &(*ops)[i - 1];
       gimple *def_stmt;
       enum tree_code code;
@@ -1258,12 +1263,12 @@ vn_reference_maybe_forwprop_address (vec<vn_reference_op_s> *ops,
 
       def_stmt = SSA_NAME_DEF_STMT (op->op0);
       if (!is_gimple_assign (def_stmt))
-    return false;
+	return changed;
 
       code = gimple_assign_rhs_code (def_stmt);
       if (code != ADDR_EXPR
 	  && code != POINTER_PLUS_EXPR)
-    return false;
+	return changed;
 
       off = poly_offset_int::from (wi::to_poly_wide (mem_op->op0), SIGNED);
 
@@ -1313,8 +1318,9 @@ vn_reference_maybe_forwprop_address (vec<vn_reference_op_s> *ops,
 	  if (!addr_base
 	      || TREE_CODE (addr_base) != MEM_REF
 	      || (TREE_CODE (TREE_OPERAND (addr_base, 0)) == SSA_NAME
-	      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (addr_base, 0))))
-	return false;
+		  && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (addr_base,
+								    0))))
+	    return changed;
 
 	  off += addr_offset;
 	  off += mem_ref_offset (addr_base);
@@ -1332,7 +1338,7 @@ vn_reference_maybe_forwprop_address (vec<vn_reference_op_s> *ops,
 		 happen when we value-number a PHI to its backedge value.  */
 	      || SSA_VAL (ptr) == op->op0
 	      || !poly_int_tree_p (ptroff))
-	return false;
+	    return changed;
 
 	  off += wi::to_poly_offset (ptroff);
 	  op->op0 = ptr;
@@ -1350,12 +1356,16 @@ vn_reference_maybe_forwprop_address (vec<vn_reference_op_s> *ops,
       if (TREE_CODE (op->op0) != SSA_NAME)
 	op->opcode = TREE_CODE (op->op0);
 
-  /* And recurse.  */
-  if (TREE_CODE (op->op0) == SSA_NAME)
-    vn_reference_maybe_forwprop_address (ops, i_p);
-  else if (TREE_CODE (op->op0) == ADDR_EXPR)
+      changed = true;
+    }
+  /* Tail-recurse.  */
+  while (TREE_CODE (op->op0) == SSA_NAME);
+
+  /* Fold a remaining *&.  */
+  if (TREE_CODE (op->op0) == ADDR_EXPR)
     vn_reference_fold_indirect (ops, i_p);
-  return true;
+
+  return changed;
 }
 
 /* Optimize the reference REF to a constant if possible or return