On 07/20/16 12:46, Richard Biener wrote:
> On Wed, 20 Jul 2016, Richard Biener wrote:
>
>> On Tue, 19 Jul 2016, Bernd Edlinger wrote:
>>
>>> Hi!
>>>
>>> As discussed at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71876,
>>> we have a _very_ old hack in gcc, that recognizes certain functions by
>>> name, and inserts in some cases unsafe attributes, that don't work for
>>> a freestanding environment.
>>>
>>> It is unsafe to return ECF_MAY_BE_ALLOCA, ECF_LEAF and ECF_NORETURN
>>> from special_function_p, just by the name of the function, especially
>>> for less well known functions, like "getcontext" or "savectx", which
>>> could easily used for something completely different.
>>
>> Returning ECF_MAY_BE_ALLOCA is safe. Just wanted to mention this,
>> regardless of the followups you already received.
>
> Oh, and maybe you can factor out the less controversical parts,
> namely ignoring the __builtin_ prefix. I don't think that
> calling __builtin_setjmp in an environment where setjmp is not a
> builtin should beave like setjmp (it will call a function named
> '__builtin_setjmp').
I wonder how I manage to dig out such contriversical things ;)
But you are right, that would at least be a start.
So this patch is what you requested:
Remove the handling of the __builtin_ prefix from special_function_p
and add the returns_twice attribute to the __builtin_setjmp declaration
instead.
Is it OK after boot-strap and regression-testing?
Thanks
Bernd.
2016-07-19 Bernd Edlinger <bernd.edlin...@hotmail.de>
PR middle-end/71876
* builtin-attrs.def (ATTR_RT_NOTHROW_LEAF_LIST): New return twice
attribute.
* builtins.def (BUILT_IN_SETJMP): Use ATTR_RT_NOTHROW_LEAF_LIST here.
* calls.c (special_function_p): Remove the special handling of the
"__builtin_" prefix.
Index: gcc/builtin-attrs.def
===================================================================
--- gcc/builtin-attrs.def (Revision 238382)
+++ gcc/builtin-attrs.def (Arbeitskopie)
@@ -131,6 +131,8 @@ DEF_ATTR_TREE_LIST (ATTR_NORETURN_NOTHROW_LIST, AT
ATTR_NULL, ATTR_NOTHROW_LIST)
DEF_ATTR_TREE_LIST (ATTR_NORETURN_NOTHROW_LEAF_LIST, ATTR_NORETURN,\
ATTR_NULL, ATTR_NOTHROW_LEAF_LIST)
+DEF_ATTR_TREE_LIST (ATTR_RT_NOTHROW_LEAF_LIST, ATTR_RETURNS_TWICE,\
+ ATTR_NULL, ATTR_NOTHROW_LEAF_LIST)
DEF_ATTR_TREE_LIST (ATTR_COLD_NOTHROW_LEAF_LIST, ATTR_COLD,\
ATTR_NULL, ATTR_NOTHROW_LEAF_LIST)
DEF_ATTR_TREE_LIST (ATTR_COLD_NORETURN_NOTHROW_LEAF_LIST, ATTR_COLD,\
Index: gcc/builtins.def
===================================================================
--- gcc/builtins.def (Revision 238382)
+++ gcc/builtins.def (Arbeitskopie)
@@ -837,7 +837,7 @@ DEF_LIB_BUILTIN (BUILT_IN_REALLOC, "realloc
DEF_GCC_BUILTIN (BUILT_IN_RETURN, "return", BT_FN_VOID_PTR, ATTR_NORETURN_NOTHROW_LEAF_LIST)
DEF_GCC_BUILTIN (BUILT_IN_RETURN_ADDRESS, "return_address", BT_FN_PTR_UINT, ATTR_LEAF_LIST)
DEF_GCC_BUILTIN (BUILT_IN_SAVEREGS, "saveregs", BT_FN_PTR_VAR, ATTR_NULL)
-DEF_GCC_BUILTIN (BUILT_IN_SETJMP, "setjmp", BT_FN_INT_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN (BUILT_IN_SETJMP, "setjmp", BT_FN_INT_PTR, ATTR_RT_NOTHROW_LEAF_LIST)
DEF_EXT_LIB_BUILTIN (BUILT_IN_STRFMON, "strfmon", BT_FN_SSIZE_STRING_SIZE_CONST_STRING_VAR, ATTR_FORMAT_STRFMON_NOTHROW_3_4)
DEF_LIB_BUILTIN (BUILT_IN_STRFTIME, "strftime", BT_FN_SIZE_STRING_SIZE_CONST_STRING_CONST_PTR, ATTR_FORMAT_STRFTIME_NOTHROW_3_0)
DEF_GCC_BUILTIN (BUILT_IN_TRAP, "trap", BT_FN_VOID, ATTR_NORETURN_NOTHROW_LEAF_LIST)
Index: gcc/calls.c
===================================================================
--- gcc/calls.c (Revision 238382)
+++ gcc/calls.c (Arbeitskopie)
@@ -514,14 +514,10 @@ special_function_p (const_tree fndecl, int flags)
&& ! strcmp (name, "alloca"))
flags |= ECF_MAY_BE_ALLOCA;
- /* Disregard prefix _, __, __x or __builtin_. */
+ /* Disregard prefix _, __ or __x. */
if (name[0] == '_')
{
- if (name[1] == '_'
- && name[2] == 'b'
- && !strncmp (name + 3, "uiltin_", 7))
- tname += 10;
- else if (name[1] == '_' && name[2] == 'x')
+ if (name[1] == '_' && name[2] == 'x')
tname += 3;
else if (name[1] == '_')
tname += 2;
