re PR middle-end/86714 (tree-ssa-forwprop.c confused by too long initializer)

	PR tree-optimization/86714
	PR tree-optimization/86711
	* builtins.c (c_strlen): Add arguments to call to string_constant.
	* expr.c (string_constant): Add argument.  Detect missing nul
	terminator and outermost declaration it's missing in.
	* expr.h (string_constant): Add argument.
	* fold-const.c (read_from_constant_string): Add arguments to call to
	string_constant.
	(c_getstr): Likewise.
	* tree-ssa-forwprop.c (simplify_builtin_call): Likewise.
	to string_constant.
	* tree-ssa-strlen.c (get_stridx): Likewise.

	PR tree-optimization/86714
	PR tree-optimization/86711
	* gcc.c-torture/execute/memchr-1.c: New test.
	* gcc.c-torture/execute/pr86714.c: New test.
	* gcc.c-torture/execute/widechar-3.c: New test.
	* gcc.dg/strlenopt-58.c: New test.

Co-Authored-By: Bernd Edlinger <bernd.edlinger@hotmail.de>
Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r263963

1 files changed, 25 insertions, 6 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index 2645c25..cd5cf12 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -11303,12 +11303,15 @@ is_aligning_offset (const_tree offset, const_tree exp)
 /* Return the tree node if an ARG corresponds to a string constant or zero
    if it doesn't.  If we return nonzero, set *PTR_OFFSET to the (possibly
    non-constant) offset in bytes within the string that ARG is accessing.
+   If NONSTR is non-null, consider valid even sequences of characters that
+   aren't nul-terminated strings.  In that case, if ARG refers to such
+   a sequence set *NONSTR to its declaration and clear it otherwise.
    The type of the offset is sizetype.  If MEM_SIZE is non-zero the storage
    size of the memory is returned.  If MEM_SIZE is zero, the string is
    only returned when it is properly zero terminated.  */
 
 tree
-string_constant (tree arg, tree *ptr_offset, tree *mem_size)
+string_constant (tree arg, tree *ptr_offset, tree *mem_size, tree *nonstr)
 {
   tree array;
   STRIP_NOPS (arg);
@@ -11362,7 +11365,7 @@ string_constant (tree arg, tree *ptr_offset, tree *mem_size)
 	return NULL_TREE;
 
       tree offset;
-      if (tree str = string_constant (arg0, &offset, mem_size))
+      if (tree str = string_constant (arg0, &offset, mem_size, nonstr))
 	{
 	  /* Avoid pointers to arrays (see bug 86622).  */
 	  if (POINTER_TYPE_P (TREE_TYPE (arg))
@@ -11404,6 +11407,9 @@ string_constant (tree arg, tree *ptr_offset, tree *mem_size)
       *ptr_offset = fold_convert (sizetype, offset);
       if (mem_size)
 	*mem_size = TYPE_SIZE_UNIT (TREE_TYPE (array));
+      /* This is not strictly correct.  FIXME in follow-up patch.  */
+      if (nonstr)
+	*nonstr = NULL_TREE;
       return array;
     }
 
@@ -11450,22 +11456,35 @@ string_constant (tree arg, tree *ptr_offset, tree *mem_size)
   if (!array_size || TREE_CODE (array_size) != INTEGER_CST)
     return NULL_TREE;
 
-  /* Avoid returning a string that doesn't fit in the array
-     it is stored in, like
+  /* Avoid returning an array that is unterminated because it lacks
+     a terminating nul, like
      const char a[4] = "abcde";
-     but do handle those that fit even if they have excess
+     but do handle those that are strings even if they have excess
      initializers, such as in
      const char a[4] = "abc\000\000";
      The excess elements contribute to TREE_STRING_LENGTH()
      but not to strlen().  */
   unsigned HOST_WIDE_INT charsize
     = tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (init))));
+  /* Compute the lower bound number of elements (not bytes) in the array
+     that the string is used to initialize.  The actual size of the array
+     may be greater if the string is shorter, but the the important
+     data point is whether the literal, inlcuding the terminating nul,
+     fits the array.  */
+  unsigned HOST_WIDE_INT array_elts
+    = tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (init))) / charsize;
+
+  /* Compute the string length in (wide) characters.  */
   unsigned HOST_WIDE_INT length = TREE_STRING_LENGTH (init);
   length = string_length (TREE_STRING_POINTER (init), charsize,
 			  length / charsize);
   if (mem_size)
     *mem_size = TYPE_SIZE_UNIT (TREE_TYPE (init));
-  else if (compare_tree_int (array_size, length + 1) < 0)
+  if (nonstr)
+    *nonstr = array_elts > length ? NULL_TREE : array;
+
+  if ((!mem_size && !nonstr)
+      && array_elts <= length)
     return NULL_TREE;
 
   *ptr_offset = offset;