Move c_getstr to fold-const.c

Upcoming patches to fold-const-call.c want to use c_getstr, which is
currently defined in builtins.c.  The function doesn't really do anything
related to built-ins, and I'd rather not make fold-const-call.c depend
on builtins.c and builtins.c depend on fold-const-call.c, so this patch
moves the function to fold-const.c instead.

Tested on x86_64-linux-gnu, aarch64-linux-gnu and arm-linux-gnueabi.

gcc/
	* builtins.h (c_getstr): Move to...
	* fold-const.h (c_getstr): ...here.
	* builtins.c (c_getstr): Move to...
	* fold-const.c (c_getstr): ...here.

From-SVN: r229919

1 files changed, 21 insertions, 0 deletions

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index fb613da..ae28445 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -14398,3 +14398,24 @@ fold_build_pointer_plus_hwi_loc (location_t loc, tree ptr, HOST_WIDE_INT off)
   return fold_build2_loc (loc, POINTER_PLUS_EXPR, TREE_TYPE (ptr),
 			  ptr, size_int (off));
 }
+
+/* Return a char pointer for a C string if it is a string constant
+   or sum of string constant and integer constant.  */
+
+const char *
+c_getstr (tree src)
+{
+  tree offset_node;
+
+  src = string_constant (src, &offset_node);
+  if (src == 0)
+    return 0;
+
+  if (offset_node == 0)
+    return TREE_STRING_POINTER (src);
+  else if (!tree_fits_uhwi_p (offset_node)
+	   || compare_tree_int (offset_node, TREE_STRING_LENGTH (src) - 1) > 0)
+    return 0;
+
+  return TREE_STRING_POINTER (src) + tree_to_uhwi (offset_node);
+}