[Bug libstdc++/14311] New: builtins for atomic operations needed

[Bug libstdc++/14311] New: builtins for atomic operations needed

[bkoz at gcc dot gnu dot org]

See:
http://gcc.gnu.org/ml/libstdc++/2004-02/msg00372.html

Currently, the atomicity.h functions are used by:

%grep "atomicity.h" include/*/*.h | grep include
include/bits/basic_string.h:#include <bits/atomicity.h>
include/bits/ios_base.h:#include <bits/atomicity.h>
include/bits/locale_classes.h:#include <bits/atomicity.h>
include/ext/mt_allocator.h:#include <bits/atomicity.h>
include/ext/pool_allocator.h:#include <bits/atomicity.h>

This includes reference counting in std::string, std::ios_base
callbacks, std::locale::facet and std::locale::_Impl, and in various
allocator classes.

Although considered useful, this implementation has one drawback: on one
popular platform, (x86/linux), switching between atomicity files for
i386 and i486 and above is not compatible. Thus, when using i486 and
above libstdc++, all C++ applications (and thus C++ packages in an os
distribution) have to be compiled for both i386 and i486+. I believe
this has been an issue for Red Hat, Debian, and perhaps BSD.

One way around this would be to make these atomic functions gcc
builtins. These would be different semantics than other gcc builtins,
however, because there could be no fall back to a support library in the
case of failure to use the builtin.

Another would be to not define these functions in headers, and instead
put them into libstdc++.so, version them, and then export them. See the
attached patch, which was discussed in last week's tools conference
call. With this, linux distributions for i386 could use

-- 
           Summary: builtins for atomic operations needed
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bkoz at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug c/14311] builtins for atomic operations needed

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-04-27 18:57 -------
Confirmed, there are some builtins without a function to fall back on.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|libstdc++                   |c
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-04-27 18:57:47
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2005-04-09 03:09 -------
I'm working on atomic builtins, but this will *not* resolve the problem of
compiling for i386 and i486+.  Indeed, it could easily make it worse because
you won't have the kind of control you did before wrt hiding these operations
in out-of-line functions.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rth at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2005-03-26 05:33:24         |2005-04-09 03:09:22
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[pcarlini at suse dot de]

------- Additional Comments From pcarlini at suse dot de  2005-04-09 07:53 -------
Can you expand a bit on that? I understand perfectly that we are not going to
have CAS for i386, but what's wrong with i486+?!?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[pcarlini at suse dot de]

------- Additional Comments From pcarlini at suse dot de  2005-04-09 08:10 -------
Ah, ok, now I got it ;) Actually, you meant exactly that i386 will *never* be
exchangeable with i486+...

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[bkoz at redhat dot com]

------- Additional Comments From bkoz at redhat dot com  2005-04-11 17:14 -------
Subject: Re:  builtins for atomic operations needed


> I'm working on atomic builtins, but this will *not* resolve the problem of
> compiling for i386 and i486+.  Indeed, it could easily make it worse because
> you won't have the kind of control you did before wrt hiding these operations
> in out-of-line functions.

Hurray. I really think that the builtin solution is the right way
forward for everybody, design-wise. Thanks for doing this Richard.

Pre gcc-3.4, we had the same problem with i386/i486+ separation. 

I think, realistically, that i486 compilation should be a minimum
requirement for linux distros circa 2005. (If not i586.). Thus, the
solution I will be in favor of is eliminating i386 compatibility with
the version of the toolchain that first implements the atomic builtins.

For people that really want to support i386, they should use gcc-2.7 to gcc-3.4.

-benjamin


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-04-14 23:37 -------
Subject: Bug 14311

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rth@gcc.gnu.org	2005-04-14 23:37:47

Modified files:
	gcc            : ChangeLog builtin-types.def builtins.c 
	                 builtins.def c-common.c c-common.h c-typeck.c 
	                 expr.c expr.h genopinit.c optabs.c optabs.h 
	gcc/doc        : extend.texi md.texi 
Added files:
	gcc/testsuite/gcc.c-torture/compile: sync-1.c 
	gcc/testsuite/gcc.dg: sync-1.c 

Log message:
	PR middle-end/14311
	* builtin-types.def (BT_BOOL, BT_VOLATILE_PTR, BT_I1, BT_I2,
	BT_I4, BT_I8, BT_FN_VOID_VPTR, BT_FN_I1_VPTR_I1, BT_FN_I2_VPTR_I2,
	BT_FN_I4_VPTR_I4, BT_FN_I8_VPTR_I8, BT_FN_BOOL_VPTR_I1_I1,
	BT_FN_BOOL_VPTR_I2_I2, BT_FN_BOOL_VPTR_I4_I4, BT_FN_BOOL_VPTR_I8_I8,
	BT_FN_I1_VPTR_I1_I1, BT_FN_I2_VPTR_I2_I2, BT_FN_I4_VPTR_I4_I4,
	BT_FN_I8_VPTR_I8_I8): New.
	* builtins.def (DEF_SYNC_BUILTIN): New.
	(BUILT_IN_FETCH_AND_ADD_N, BUILT_IN_FETCH_AND_ADD_1,
	BUILT_IN_FETCH_AND_ADD_2, BUILT_IN_FETCH_AND_ADD_4,
	BUILT_IN_FETCH_AND_ADD_8, BUILT_IN_FETCH_AND_SUB_N,
	BUILT_IN_FETCH_AND_SUB_1, BUILT_IN_FETCH_AND_SUB_2,
	BUILT_IN_FETCH_AND_SUB_4, BUILT_IN_FETCH_AND_SUB_8,
	BUILT_IN_FETCH_AND_OR_N, BUILT_IN_FETCH_AND_OR_1,
	BUILT_IN_FETCH_AND_OR_2, BUILT_IN_FETCH_AND_OR_4,
	BUILT_IN_FETCH_AND_OR_8, BUILT_IN_FETCH_AND_AND_N,
	BUILT_IN_FETCH_AND_AND_1, BUILT_IN_FETCH_AND_AND_2,
	BUILT_IN_FETCH_AND_AND_4, BUILT_IN_FETCH_AND_AND_8,
	BUILT_IN_FETCH_AND_XOR_N, BUILT_IN_FETCH_AND_XOR_1,
	BUILT_IN_FETCH_AND_XOR_2, BUILT_IN_FETCH_AND_XOR_4,
	BUILT_IN_FETCH_AND_XOR_8, BUILT_IN_FETCH_AND_NAND_N,
	BUILT_IN_FETCH_AND_NAND_1, BUILT_IN_FETCH_AND_NAND_2,
	BUILT_IN_FETCH_AND_NAND_4, BUILT_IN_FETCH_AND_NAND_8,
	BUILT_IN_ADD_AND_FETCH_N, BUILT_IN_ADD_AND_FETCH_1,
	BUILT_IN_ADD_AND_FETCH_2, BUILT_IN_ADD_AND_FETCH_4,
	BUILT_IN_ADD_AND_FETCH_8, BUILT_IN_SUB_AND_FETCH_N,
	BUILT_IN_SUB_AND_FETCH_1, BUILT_IN_SUB_AND_FETCH_2,
	BUILT_IN_SUB_AND_FETCH_4, BUILT_IN_SUB_AND_FETCH_8,
	BUILT_IN_OR_AND_FETCH_N, BUILT_IN_OR_AND_FETCH_1,
	BUILT_IN_OR_AND_FETCH_2, BUILT_IN_OR_AND_FETCH_4,
	BUILT_IN_OR_AND_FETCH_8, BUILT_IN_AND_AND_FETCH_N,
	BUILT_IN_AND_AND_FETCH_1, BUILT_IN_AND_AND_FETCH_2,
	BUILT_IN_AND_AND_FETCH_4, BUILT_IN_AND_AND_FETCH_8,
	BUILT_IN_XOR_AND_FETCH_N, BUILT_IN_XOR_AND_FETCH_1,
	BUILT_IN_XOR_AND_FETCH_2, BUILT_IN_XOR_AND_FETCH_4,
	BUILT_IN_XOR_AND_FETCH_8, BUILT_IN_NAND_AND_FETCH_N,
	BUILT_IN_NAND_AND_FETCH_1, BUILT_IN_NAND_AND_FETCH_2,
	BUILT_IN_NAND_AND_FETCH_4, BUILT_IN_NAND_AND_FETCH_8,
	BUILT_IN_BOOL_COMPARE_AND_SWAP_N, BUILT_IN_BOOL_COMPARE_AND_SWAP_1,
	BUILT_IN_BOOL_COMPARE_AND_SWAP_2, BUILT_IN_BOOL_COMPARE_AND_SWAP_4,
	BUILT_IN_BOOL_COMPARE_AND_SWAP_8, BUILT_IN_VAL_COMPARE_AND_SWAP_N,
	BUILT_IN_VAL_COMPARE_AND_SWAP_1, BUILT_IN_VAL_COMPARE_AND_SWAP_2,
	BUILT_IN_VAL_COMPARE_AND_SWAP_4, BUILT_IN_VAL_COMPARE_AND_SWAP_8,
	BUILT_IN_LOCK_TEST_AND_SET_N, BUILT_IN_LOCK_TEST_AND_SET_1,
	BUILT_IN_LOCK_TEST_AND_SET_2, BUILT_IN_LOCK_TEST_AND_SET_4,
	BUILT_IN_LOCK_TEST_AND_SET_8, BUILT_IN_LOCK_RELEASE_N,
	BUILT_IN_LOCK_RELEASE_1, BUILT_IN_LOCK_RELEASE_2,
	BUILT_IN_LOCK_RELEASE_4, BUILT_IN_LOCK_RELEASE_8,
	BUILT_IN_SYNCHRONIZE: New.
	* builtins.c (called_as_built_in): Rewrite from CALLED_AS_BUILT_IN
	as a function.  Accept __sync_ as a prefix as well.
	(expand_builtin_sync_operation, expand_builtin_compare_and_swap,
	expand_builtin_lock_test_and_set, expand_builtin_synchronize,
	expand_builtin_lock_release): New.
	(expand_builtin): Call them.
	* c-common.c (DEF_BUILTIN): Don't require __builtin_ prefix if
	neither BOTH_P nor FALLBACK_P are defined.
	(builtin_type_for_size): New.
	(sync_resolve_size, sync_resolve_params, sync_resolve_return): New.
	(resolve_overloaded_builtin): New.
	* c-common.h (resolve_overloaded_builtin): Declare.
	(builtin_type_for_size): Declare.
	* c-typeck.c (build_function_call): Invoke resolve_overloaded_builtin.
	* expr.c (sync_add_optab, sync_sub_optab, sync_ior_optab,
	sync_and_optab, sync_xor_optab, sync_nand_optab, sync_old_add_optab,
	sync_old_sub_optab, sync_old_ior_optab, sync_old_and_optab,
	sync_old_xor_optab, sync_old_nand_optab, sync_new_add_optab,
	sync_new_sub_optab, sync_new_ior_optab, sync_new_and_optab,
	sync_new_xor_optab, sync_new_nand_optab, sync_compare_and_swap,
	sync_compare_and_swap_cc, sync_lock_test_and_set,
	sync_lock_release): New.
	* optabs.h: Declare them.
	* expr.h (expand_val_compare_and_swap, expand_bool_compare_and_swap,
	expand_sync_operation, expand_sync_fetch_operation,
	expand_sync_lock_test_and_set): Declare.
	* genopinit.c (optabs): Add sync optabs.
	* optabs.c (init_optabs): Initialize sync optabs.
	(expand_val_compare_and_swap_1, expand_val_compare_and_swap,
	expand_bool_compare_and_swap, expand_compare_and_swap_loop,
	expand_sync_operation, expand_sync_fetch_operation,
	expand_sync_lock_test_and_set): New.
	* doc/extend.texi (Atomic Builtins): New section
	* doc/md.texi (Standard Names): Add sync patterns.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.8294&r2=2.8295
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/builtin-types.def.diff?cvsroot=gcc&r1=1.30&r2=1.31
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/builtins.c.diff?cvsroot=gcc&r1=1.452&r2=1.453
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/builtins.def.diff?cvsroot=gcc&r1=1.101&r2=1.102
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/c-common.c.diff?cvsroot=gcc&r1=1.621&r2=1.622
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/c-common.h.diff?cvsroot=gcc&r1=1.283&r2=1.284
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/c-typeck.c.diff?cvsroot=gcc&r1=1.431&r2=1.432
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/expr.c.diff?cvsroot=gcc&r1=1.783&r2=1.784
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/expr.h.diff?cvsroot=gcc&r1=1.186&r2=1.187
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/genopinit.c.diff?cvsroot=gcc&r1=1.91&r2=1.92
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/optabs.c.diff?cvsroot=gcc&r1=1.270&r2=1.271
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/optabs.h.diff?cvsroot=gcc&r1=1.54&r2=1.55
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/doc/extend.texi.diff?cvsroot=gcc&r1=1.250&r2=1.251
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/doc/md.texi.diff?cvsroot=gcc&r1=1.128&r2=1.129
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.c-torture/compile/sync-1.c.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/sync-1.c.diff?cvsroot=gcc&r1=NONE&r2=1.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-04-16 02:07 -------
Subject: Bug 14311

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rth@gcc.gnu.org	2005-04-16 02:07:33

Modified files:
	gcc/cp         : ChangeLog semantics.c 
Added files:
	gcc/testsuite/g++.dg/ext: sync-1.C sync-2.C 

Log message:
	PR middle-end/14311
	* semantics.c (finish_call_expr): Call resolve_overloaded_builtin.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4707&r2=1.4708
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/semantics.c.diff?cvsroot=gcc&r1=1.467&r2=1.468
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/sync-1.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/sync-2.C.diff?cvsroot=gcc&r1=NONE&r2=1.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311

[Bug middle-end/14311] builtins for atomic operations needed

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2005-04-16 02:08 -------
Middle-end bits are done.  Target maintainers need to update md files
for new patterns, but i686 and ia64 are done.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14311