PR27095, builtin_expand_memset multiple arg expansion

[Alan Modra <amodra at bigpond dot net dot au>]

:ADDPATCH middle-end:

Some time ago, Roger fixed a similar problem with expand_builtin_strcmp
to this one with expand_builtin_memset.  I've followed Roger's lead in
stopping multiple expansion of args by wrapping the args in a save_expr
and, if the builtin expansion fails for some reason, expanding the
libcall using the wrapped args.  As far as I can see, other builtin
string functions don't need similar fixes, but while I was checking them
I noticed that a bug had crept into expand_builtin_strcmp.

Bootstrapped and regression tested powerpc64-linux.  OK mainline and
4.1?

	PR middle-end/27095
	* builtins.c: (expand_builtin_memset): Stabilize args before expansion
	and emit libcall here in case the builtin fails.
	(expand_builtin_strcmp): Always emit the libcall here on failure.

Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c	(revision 112911)
+++ gcc/builtins.c	(working copy)
@@ -3390,12 +3390,14 @@ expand_builtin_memset (tree arglist, rtx
       tree dest = TREE_VALUE (arglist);
       tree val = TREE_VALUE (TREE_CHAIN (arglist));
       tree len = TREE_VALUE (TREE_CHAIN (TREE_CHAIN (arglist)));
+      tree fndecl, fn;
+      enum built_in_function fcode;
       char c;
-
-      unsigned int dest_align
-	= get_pointer_alignment (dest, BIGGEST_ALIGNMENT);
+      unsigned int dest_align;
       rtx dest_mem, dest_addr, len_rtx;
 
+      dest_align = get_pointer_alignment (dest, BIGGEST_ALIGNMENT);
+
       /* If DEST is not a pointer type, don't do this
 	 operation in-line.  */
       if (dest_align == 0)
@@ -3409,15 +3411,21 @@ expand_builtin_memset (tree arglist, rtx
 	  return expand_expr (dest, target, mode, EXPAND_NORMAL);
 	}
 
+      /* Stabilize the arguments in case we fail.  */
+      dest = builtin_save_expr (dest);
+      val = builtin_save_expr (val);
+      len = builtin_save_expr (len);
+
       len_rtx = expand_normal (len);
       dest_mem = get_memory_rtx (dest, len);
 
       if (TREE_CODE (val) != INTEGER_CST)
 	{
+	  tree cval;
 	  rtx val_rtx;
 
-	  val = fold_build1 (CONVERT_EXPR, unsigned_char_type_node, val);
-	  val_rtx = expand_normal (val);
+	  cval = fold_build1 (CONVERT_EXPR, unsigned_char_type_node, val);
+	  val_rtx = expand_normal (cval);
 
 	  /* Assume that we can memset by pieces if we can store the
 	   * the coefficients by pieces (in the required modes).
@@ -3433,9 +3441,9 @@ expand_builtin_memset (tree arglist, rtx
 	      store_by_pieces (dest_mem, tree_low_cst (len, 1),
 			       builtin_memset_gen_str, val_rtx, dest_align, 0);
 	    }
-	  else if (!set_storage_via_setmem(dest_mem, len_rtx, val_rtx, 
-					   dest_align))
-	    return 0;
+	  else if (!set_storage_via_setmem (dest_mem, len_rtx, val_rtx, 
+					    dest_align))
+	    goto do_libcall;
 
 	  dest_mem = force_operand (XEXP (dest_mem, 0), NULL_RTX);
 	  dest_mem = convert_memory_address (ptr_mode, dest_mem);
@@ -3443,7 +3451,7 @@ expand_builtin_memset (tree arglist, rtx
 	}
 
       if (target_char_cast (val, &c))
-	return 0;
+	goto do_libcall;
 
       if (c)
 	{
@@ -3455,7 +3463,7 @@ expand_builtin_memset (tree arglist, rtx
 			     builtin_memset_read_str, &c, dest_align, 0);
 	  else if (!set_storage_via_setmem (dest_mem, len_rtx, GEN_INT (c),
 					    dest_align))
-	    return 0;
+	    goto do_libcall;
 
 	  dest_mem = force_operand (XEXP (dest_mem, 0), NULL_RTX);
 	  dest_mem = convert_memory_address (ptr_mode, dest_mem);
@@ -3474,6 +3482,19 @@ expand_builtin_memset (tree arglist, rtx
 	}
 
       return dest_addr;
+
+    do_libcall:
+      fndecl = get_callee_fndecl (orig_exp);
+      fcode = DECL_FUNCTION_CODE (fndecl);
+      gcc_assert (fcode == BUILT_IN_MEMSET || fcode == BUILT_IN_BZERO);
+      arglist = build_tree_list (NULL_TREE, len);
+      if (fcode == BUILT_IN_MEMSET)
+	arglist = tree_cons (NULL_TREE, val, arglist);
+      arglist = tree_cons (NULL_TREE, dest, arglist);
+      fn = build_function_call_expr (fndecl, arglist);
+      if (TREE_CODE (fn) == CALL_EXPR)
+	CALL_EXPR_TAILCALL (fn) = CALL_EXPR_TAILCALL (orig_exp);
+      return expand_call (fn, target, target == const0_rtx);
     }
 }
 
@@ -3719,9 +3740,8 @@ expand_builtin_strcmp (tree exp, rtx tar
 
 	  /* If both arguments have side effects, we cannot optimize.  */
 	  if (!len || TREE_SIDE_EFFECTS (len))
-	    return 0;
+	    goto do_libcall;
 
-	  /* Stabilize the arguments in case gen_cmpstrnsi fails.  */
 	  arg3_rtx = expand_normal (len);
 
 	  /* Make a place to write the result of the instruction.  */
@@ -3752,6 +3772,7 @@ expand_builtin_strcmp (tree exp, rtx tar
 
       /* Expand the library call ourselves using a stabilized argument
 	 list to avoid re-evaluating the function's arguments twice.  */
+    do_libcall:
       arglist = build_tree_list (NULL_TREE, arg2);
       arglist = tree_cons (NULL_TREE, arg1, arglist);
       fndecl = get_callee_fndecl (exp);

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre