re PR c++/82084 (ICE: constructing wstring with -O3)

2017-09-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/82084
	* fold-const.h (can_native_encode_string_p): Declare.
	* fold-const.c (can_native_encode_string_p): Factor out from ...
	(native_encode_string): ... here.
	* tree-vect-stmts.c (vectorizable_store): Call it to avoid
	vectorizing stores from constants we later cannot handle.

	* g++.dg/torture/pr82084.C: New testcase.

From-SVN: r251661

gcc/ChangeLog

+2017-09-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/82084
+	* fold-const.h (can_native_encode_string_p): Declare.
+	* fold-const.c (can_native_encode_string_p): Factor out from ...
+	(native_encode_string): ... here.
+	* tree-vect-stmts.c (vectorizable_store): Call it to avoid
+	vectorizing stores from constants we later cannot handle.
+
 2017-09-04  Marek Polacek  <polacek@redhat.com>
 
 	PR c/81783

gcc/fold-const.c

@@ -7184,16 +7184,10 @@ native_encode_vector (const_tree expr, unsigned char *ptr, int len, int off)
 static int
 native_encode_string (const_tree expr, unsigned char *ptr, int len, int off)
 {
-  tree type = TREE_TYPE (expr);
-  HOST_WIDE_INT total_bytes;
-
-  if (TREE_CODE (type) != ARRAY_TYPE
-      || TREE_CODE (TREE_TYPE (type)) != INTEGER_TYPE
-      || (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE (TREE_TYPE (type)))
-	  != BITS_PER_UNIT)
-      || !tree_fits_shwi_p (TYPE_SIZE_UNIT (type)))
+  if (! can_native_encode_string_p (expr))
     return 0;
-  total_bytes = tree_to_shwi (TYPE_SIZE_UNIT (type));
+
+  HOST_WIDE_INT total_bytes = tree_to_shwi (TYPE_SIZE_UNIT (TREE_TYPE (expr)));
   if ((off == -1 && total_bytes > len)
       || off >= total_bytes)
     return 0;
@@ -7487,6 +7481,23 @@ can_native_encode_type_p (tree type)
     }
 }
 
+/* Return true iff a STRING_CST S is accepted by
+   native_encode_expr.  */
+
+bool
+can_native_encode_string_p (const_tree expr)
+{
+  tree type = TREE_TYPE (expr);
+
+  if (TREE_CODE (type) != ARRAY_TYPE
+      || TREE_CODE (TREE_TYPE (type)) != INTEGER_TYPE
+      || (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE (TREE_TYPE (type)))
+	  != BITS_PER_UNIT)
+      || !tree_fits_shwi_p (TYPE_SIZE_UNIT (type)))
+    return false;
+  return true;
+}
+
 /* Fold a VIEW_CONVERT_EXPR of a constant expression EXPR to type
    TYPE at compile-time.  If we're unable to perform the conversion
    return NULL_TREE.  */

gcc/fold-const.h

@@ -28,6 +28,7 @@ extern int folding_initializer;
 extern int native_encode_expr (const_tree, unsigned char *, int, int off = -1);
 extern tree native_interpret_expr (tree, const unsigned char *, int);
 extern bool can_native_encode_type_p (tree);
+extern bool can_native_encode_string_p (const_tree);
 
 /* Fold constants as much as possible in an expression.
    Returns the simplified expression.

gcc/testsuite/ChangeLog

+2017-09-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/82084
+	* g++.dg/torture/pr82084.C: New testcase.
+
 2017-09-04  Marek Polacek  <polacek@redhat.com>
 
 	PR c/81783

gcc/testsuite/g++.dg/torture/pr82084.C

+// { dg-do compile }
+
+#include <string>
+int main()
+{
+  wchar_t strs[4][2]= {  L"A", L"B", L"C" , L"D"};
+  std::wstring ss(strs[0]);
+  return 0;
+}

gcc/tree-vect-stmts.c

@@ -5733,6 +5733,12 @@ vectorizable_store (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
 
   op = gimple_assign_rhs1 (stmt);
 
+  /* In the case this is a store from a STRING_CST make sure
+     native_encode_expr can handle it.  */
+  if (TREE_CODE (op) == STRING_CST
+      && ! can_native_encode_string_p (op))
+    return false;
+
   if (!vect_is_simple_use (op, vinfo, &def_stmt, &dt, &rhs_vectype))
     {
       if (dump_enabled_p ())