re PR tree-optimization/78847 (pointer arithmetic from c++ ranged-based for loop not optimized)

2017-04-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78847
	* fold-const.c (split_tree): Handle POINTER_PLUS_EXPR.

	* g++.dg/tree-ssa/pr78847.C: New testcase.

From-SVN: r247061

gcc/ChangeLog

 2017-04-21  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/78847
+	* fold-const.c (split_tree): Handle POINTER_PLUS_EXPR.
+
+2017-04-21  Richard Biener  <rguenther@suse.de>
+
 	* tree.h (build_qualified_type): Annotate with CXX_MEM_STAT_INFO.
 	(build_distinct_type_copy): Likewise.
 	(build_variant_type_copy): Likewise.

gcc/fold-const.c

@@ -798,8 +798,11 @@ split_tree (location_t loc, tree in, tree type, enum tree_code code,
 		  though the C standard doesn't say so) for integers because
 		  the value is not affected.  For reals, the value might be
 		  affected, so we can't.  */
-	       && ((code == PLUS_EXPR && TREE_CODE (in) == MINUS_EXPR)
-		   || (code == MINUS_EXPR && TREE_CODE (in) == PLUS_EXPR))))
+	       && ((code == PLUS_EXPR && TREE_CODE (in) == POINTER_PLUS_EXPR)
+		   || (code == PLUS_EXPR && TREE_CODE (in) == MINUS_EXPR)
+		   || (code == MINUS_EXPR
+		       && (TREE_CODE (in) == PLUS_EXPR
+			   || TREE_CODE (in) == POINTER_PLUS_EXPR)))))
     {
       tree op0 = TREE_OPERAND (in, 0);
       tree op1 = TREE_OPERAND (in, 1);

gcc/testsuite/ChangeLog

+2017-04-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78847
+	* g++.dg/tree-ssa/pr78847.C: New testcase.
+
 2017-04-21  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/80468

gcc/testsuite/g++.dg/tree-ssa/pr78847.C

+/* { dg-do compile } */
+/* { dg-require-effective-target c++14 } */
+/* { dg-options "-O3 -fdump-tree-ldist" } */
+
+#include <stddef.h>
+#include <cstring>
+#include <experimental/string_view>
+
+using string_view = std::experimental::string_view;
+
+class Foo {
+    constexpr static size_t Length = 9;
+    char ascii_[Length];
+public:
+    Foo();
+    string_view view() const {
+	return string_view(ascii_, Length);
+    }
+};
+
+void testWithLoopValue(const Foo foo, size_t ptr, char *buf_) {
+    for (auto c : foo.view())
+      buf_[ptr++] = c;
+}
+
+/* { dg-final { scan-tree-dump "memcpy\[^\n\r\]*, 9\\);" "ldist" } } */