[PATCH][RFC] Fix PR59860

[Jakub Jelinek]

On Mon, Jan 20, 2014 at 03:53:08PM +0100, Richard Biener wrote:
> That works for me.

Ok, here is what I've committed after bootstrap/regtest on x86_64-linux
and i686-linux.

2014-01-20  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/59860
	* tree.h (fold_builtin_strcat): New prototype.
	* builtins.c (fold_builtin_strcat): No longer static.  Add len
	argument, if non-NULL, don't call c_strlen.  Optimize
	directly into __builtin_memcpy instead of __builtin_strcpy.
	(fold_builtin_2): Adjust fold_builtin_strcat caller.
	* gimple-fold.c (gimple_fold_builtin): Handle BUILT_IN_STRCAT.

--- gcc/tree.h.jj	2014-01-20 19:15:58.097104985 +0100
+++ gcc/tree.h	2014-01-20 19:16:29.690942814 +0100
@@ -4527,6 +4527,7 @@ extern tree fold_call_expr (location_t,
 extern tree fold_builtin_fputs (location_t, tree, tree, bool, bool, tree);
 extern tree fold_builtin_strcpy (location_t, tree, tree, tree, tree);
 extern tree fold_builtin_strncpy (location_t, tree, tree, tree, tree, tree);
+extern tree fold_builtin_strcat (location_t, tree, tree, tree);
 extern tree fold_builtin_memory_chk (location_t, tree, tree, tree, tree, tree, tree, bool,
 				     enum built_in_function);
 extern tree fold_builtin_stxcpy_chk (location_t, tree, tree, tree, tree, tree, bool,
--- gcc/builtins.c.jj	2014-01-20 14:50:23.478809316 +0100
+++ gcc/builtins.c	2014-01-20 19:15:58.100104951 +0100
@@ -191,7 +191,6 @@ static tree fold_builtin_varargs (locati
 static tree fold_builtin_strpbrk (location_t, tree, tree, tree);
 static tree fold_builtin_strstr (location_t, tree, tree, tree);
 static tree fold_builtin_strrchr (location_t, tree, tree, tree);
-static tree fold_builtin_strcat (location_t, tree, tree);
 static tree fold_builtin_strncat (location_t, tree, tree, tree);
 static tree fold_builtin_strspn (location_t, tree, tree);
 static tree fold_builtin_strcspn (location_t, tree, tree);
@@ -10787,7 +10786,7 @@ fold_builtin_2 (location_t loc, tree fnd
       return fold_builtin_strstr (loc, arg0, arg1, type);
 
     case BUILT_IN_STRCAT:
-      return fold_builtin_strcat (loc, arg0, arg1);
+      return fold_builtin_strcat (loc, arg0, arg1, NULL_TREE);
 
     case BUILT_IN_STRSPN:
       return fold_builtin_strspn (loc, arg0, arg1);
@@ -11736,8 +11735,9 @@ fold_builtin_strpbrk (location_t loc, tr
    COMPOUND_EXPR in the chain will contain the tree for the simplified
    form of the builtin function call.  */
 
-static tree
-fold_builtin_strcat (location_t loc ATTRIBUTE_UNUSED, tree dst, tree src)
+tree
+fold_builtin_strcat (location_t loc ATTRIBUTE_UNUSED, tree dst, tree src,
+		     tree len)
 {
   if (!validate_arg (dst, POINTER_TYPE)
       || !validate_arg (src, POINTER_TYPE))
@@ -11755,14 +11755,15 @@ fold_builtin_strcat (location_t loc ATTR
 	  /* See if we can store by pieces into (dst + strlen(dst)).  */
 	  tree newdst, call;
 	  tree strlen_fn = builtin_decl_implicit (BUILT_IN_STRLEN);
-	  tree strcpy_fn = builtin_decl_implicit (BUILT_IN_STRCPY);
+	  tree memcpy_fn = builtin_decl_implicit (BUILT_IN_MEMCPY);
 
-	  if (!strlen_fn || !strcpy_fn)
+	  if (!strlen_fn || !memcpy_fn)
 	    return NULL_TREE;
 
 	  /* If the length of the source string isn't computable don't
-	     split strcat into strlen and strcpy.  */
-	  tree len = c_strlen (src, 1);
+	     split strcat into strlen and memcpy.  */
+	  if (! len)
+	    len = c_strlen (src, 1);
 	  if (! len || TREE_SIDE_EFFECTS (len))
 	    return NULL_TREE;
 
@@ -11776,7 +11777,11 @@ fold_builtin_strcat (location_t loc ATTR
 	  newdst = fold_build_pointer_plus_loc (loc, dst, newdst);
 	  newdst = builtin_save_expr (newdst);
 
-	  call = build_call_expr_loc (loc, strcpy_fn, 2, newdst, src);
+	  len = fold_convert_loc (loc, size_type_node, len);
+	  len = size_binop_loc (loc, PLUS_EXPR, len,
+				build_int_cst (size_type_node, 1));
+
+	  call = build_call_expr_loc (loc, memcpy_fn, 3, newdst, src, len);
 	  return build2 (COMPOUND_EXPR, TREE_TYPE (dst), call, dst);
 	}
       return NULL_TREE;
--- gcc/gimple-fold.c.jj	2014-01-17 21:50:10.950966672 +0100
+++ gcc/gimple-fold.c	2014-01-20 19:15:58.101104941 +0100
@@ -921,6 +921,7 @@ gimple_fold_builtin (gimple stmt)
       break;
     case BUILT_IN_STRCPY:
     case BUILT_IN_STRNCPY:
+    case BUILT_IN_STRCAT:
       arg_idx = 1;
       type = 0;
       break;
@@ -996,6 +997,13 @@ gimple_fold_builtin (gimple stmt)
 				       val[1]);
       break;
 
+    case BUILT_IN_STRCAT:
+      if (val[1] && is_gimple_val (val[1]) && nargs == 2)
+	result = fold_builtin_strcat (loc, gimple_call_arg (stmt, 0),
+				      gimple_call_arg (stmt, 1),
+				      val[1]);
+      break;
+
     case BUILT_IN_FPUTS:
       if (nargs == 2)
 	result = fold_builtin_fputs (loc, gimple_call_arg (stmt, 0),


	Jakub