Hi,
Someone privately pointed out that the ARM and AArch64 ports do not
define TARGET_RELAXED_ORDERING given that the architecture(s) mandates a
weak memory model. This patch fixes it for AArch64, the ARM patch
follows in due course after appropriate testing.
I will also note that we can define __test_and_acquire as well as
__set_and_release and I'm toying with a follow-up patch for the same.
Also it may make sense to consider changing the defaults to a safer
form, or indeed forcing ports to define some of this rather than
allowing for silent wrong code issues. However I'm not about to do so in
the context of this patch.
Bootstrapped and regression tested on aarch64-none-linux-gnu with no
regressions.
Ok to apply to trunk and all release branches ?
gcc/
PR target/66200
* config/aarch64/aarch64.c (TARGET_RELAXED_ORDERING): Define
libstdc++-v3/
PR target/66200
* configure.host (host_cpu): Add aarch64 case.
* config/cpu/aarch64/atomic_word.h: New file
regards
Ramana
P.S. It's interesting to note that ia64 doesn't define the barriers
which appear to be used in a number of other places than just the
constructor guard functions (probably wrongly on the assumption that one
doesn't need the barriers elsewhere). I suspect other architectures like
MIPS may also be affected by this.
commit 414345c424fa020717c6c3083089cd987f3032db
Author: Ramana Radhakrishnan <ramana.radhakrish...@arm.com>
Date: Wed May 20 13:55:44 2015 +0100
Add relaxed memory ordering cases.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 7f0cc0d..273aa06 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -11644,6 +11644,9 @@ aarch64_gen_adjusted_ldpstp (rtx *operands, bool load,
#undef TARGET_SCHED_FUSION_PRIORITY
#define TARGET_SCHED_FUSION_PRIORITY aarch64_sched_fusion_priority
+#undef TARGET_RELAXED_ORDERING
+#define TARGET_RELAXED_ORDERING true
+
struct gcc_target targetm = TARGET_INITIALIZER;
#include "gt-aarch64.h"
diff --git a/libstdc++-v3/config/cpu/aarch64/atomic_word.h
b/libstdc++-v3/config/cpu/aarch64/atomic_word.h
new file mode 100644
index 0000000..4afe6ed
--- /dev/null
+++ b/libstdc++-v3/config/cpu/aarch64/atomic_word.h
@@ -0,0 +1,44 @@
+// Low-level type for atomic operations -*- C++ -*-
+
+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file atomic_word.h
+ * This file is a GNU extension to the Standard C++ Library.
+ */
+
+#ifndef _GLIBCXX_ATOMIC_WORD_H
+#define _GLIBCXX_ATOMIC_WORD_H 1
+
+
+typedef int _Atomic_word;
+
+// This one prevents loads from being hoisted across the barrier;
+// in other words, this is a Load-Load acquire barrier.
+// This is necessary iff TARGET_RELAXED_ORDERING is defined in tm.h.
+#define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("dmb ishld":::"memory")
+
+// This one prevents stores from being sunk across the barrier; in other
+// words, a Store-Store release barrier.
+#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("dmb ishst":::"memory")
+
+#endif
diff --git a/libstdc++-v3/configure.host b/libstdc++-v3/configure.host
index a349ce3..42a45d9 100644
--- a/libstdc++-v3/configure.host
+++ b/libstdc++-v3/configure.host
@@ -153,6 +153,9 @@ esac
# Most can just use generic.
# THIS TABLE IS SORTED. KEEP IT THAT WAY.
case "${host_cpu}" in
+ aarch64*)
+ atomic_word_dir=cpu/aarch64
+ ;;
alpha*)
atomic_word_dir=cpu/alpha
;;
