* [Patch AArch64] Add cpu_defines.h for AArch64.
@ 2015-05-19 13:04 Ramana Radhakrishnan
2015-05-19 16:00 ` pinskia
0 siblings, 1 reply; 4+ messages in thread
From: Ramana Radhakrishnan @ 2015-05-19 13:04 UTC (permalink / raw)
To: gcc-patches, libstdc++
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Hi,
Like the ARM port, the AArch64 ports needs to set glibc_integral_traps
to false as integer divide instructions do not trap.
Bootstrapped and regression tested on aarch64-none-linux-gnu
Ok to apply ?
regards
Ramana
2015-05-17 Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
* configure.host: Define cpu_defines_dir for AArch64
* config/cpu/aarch64/cpu_defines.h: New file.
[-- Attachment #2: 0002-Do-the-same-for-AArch64.patch --]
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From 1e38b2a848a313e5b98494094b198b7a1e34c59c Mon Sep 17 00:00:00 2001
From: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Date: Mon, 18 May 2015 15:45:49 +0100
Subject: [PATCH 2/2] Do the same for AArch64.
---
libstdc++-v3/config/cpu/aarch64/cpu_defines.h | 36 +++++++++++++++++++++++++++
libstdc++-v3/configure.host | 3 +++
2 files changed, 39 insertions(+)
create mode 100644 libstdc++-v3/config/cpu/aarch64/cpu_defines.h
diff --git a/libstdc++-v3/config/cpu/aarch64/cpu_defines.h b/libstdc++-v3/config/cpu/aarch64/cpu_defines.h
new file mode 100644
index 0000000..d5a6fd0
--- /dev/null
+++ b/libstdc++-v3/config/cpu/aarch64/cpu_defines.h
@@ -0,0 +1,36 @@
+// Specific definitions for generic platforms -*- 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 bits/cpu_defines.h
+ * This is an internal header file, included by other library headers.
+ * Do not attempt to use it directly. @headername{iosfwd}
+ */
+
+#ifndef _GLIBCXX_CPU_DEFINES
+#define _GLIBCXX_CPU_DEFINES 1
+
+// Integer divide instructions don't trap on AArch64.
+#define __glibcxx_integral_traps false
+
+#endif
diff --git a/libstdc++-v3/configure.host b/libstdc++-v3/configure.host
index 465a40a..b1ca7b7 100644
--- a/libstdc++-v3/configure.host
+++ b/libstdc++-v3/configure.host
@@ -143,6 +143,9 @@ cpu_include_dir=cpu/${try_cpu}
# Set specific CPU overrides for cpu_defines_dir. Most can just use generic.
# THIS TABLE IS SORTED. KEEP IT THAT WAY.
case "${host_cpu}" in
+ aarch64*)
+ cpu_defines_dir=cpu/aarch64
+ ;;
arm*)
cpu_defines_dir=cpu/arm
;;
--
1.9.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Patch AArch64] Add cpu_defines.h for AArch64.
2015-05-19 13:04 [Patch AArch64] Add cpu_defines.h for AArch64 Ramana Radhakrishnan
@ 2015-05-19 16:00 ` pinskia
2015-05-19 16:12 ` Ramana Radhakrishnan
0 siblings, 1 reply; 4+ messages in thread
From: pinskia @ 2015-05-19 16:00 UTC (permalink / raw)
To: Ramana Radhakrishnan; +Cc: gcc-patches, libstdc++
> On May 19, 2015, at 5:54 AM, Ramana Radhakrishnan <ramana.radhakrishnan@foss.arm.com> wrote:
>
> Hi,
>
> Like the ARM port, the AArch64 ports needs to set glibc_integral_traps to false as integer divide instructions do not trap.
>
> Bootstrapped and regression tested on aarch64-none-linux-gnu
>
> Ok to apply ?
Not really questioning your patch but questioning libstdc++'s defaults. I wonder if this should be the default as most targets don't trap, only a few that does. And it should be safer default to say they don't trap too?
Thanks,
Andrew
>
> regards
> Ramana
>
>
> 2015-05-17 Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
>
> * configure.host: Define cpu_defines_dir for AArch64
> * config/cpu/aarch64/cpu_defines.h: New file.
> <0002-Do-the-same-for-AArch64.patch>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Patch AArch64] Add cpu_defines.h for AArch64.
2015-05-19 16:00 ` pinskia
@ 2015-05-19 16:12 ` Ramana Radhakrishnan
2015-05-21 11:10 ` Szabolcs Nagy
0 siblings, 1 reply; 4+ messages in thread
From: Ramana Radhakrishnan @ 2015-05-19 16:12 UTC (permalink / raw)
To: Andrew Pinski; +Cc: Ramana Radhakrishnan, gcc-patches, libstdc++
On Tue, May 19, 2015 at 4:54 PM, <pinskia@gmail.com> wrote:
>
>
>
>
>> On May 19, 2015, at 5:54 AM, Ramana Radhakrishnan <ramana.radhakrishnan@foss.arm.com> wrote:
>>
>> Hi,
>>
>> Like the ARM port, the AArch64 ports needs to set glibc_integral_traps to false as integer divide instructions do not trap.
>>
>> Bootstrapped and regression tested on aarch64-none-linux-gnu
>>
>> Ok to apply ?
>
> Not really questioning your patch but questioning libstdc++'s defaults.
> I wonder if this should be the default as most targets don't trap, only a few that does. And it should be safer default to say they don't trap too?
How about we #error out if targets do *not* define some of these
defaults in libstdc++ ? There are far more ports with weak memory
models, and the defaults for _GLIBCXX_READ/WRITE_BARRIER also appear
unsafe . I was toying with a patch like that to force targets to
define this sort of thing but I need to read more of configure.host
before I make up my mind.
regards
Ramana
>
> Thanks,
> Andrew
>
>
>>
>> regards
>> Ramana
>>
>>
>> 2015-05-17 Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
>>
>> * configure.host: Define cpu_defines_dir for AArch64
>> * config/cpu/aarch64/cpu_defines.h: New file.
>> <0002-Do-the-same-for-AArch64.patch>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Patch AArch64] Add cpu_defines.h for AArch64.
2015-05-19 16:12 ` Ramana Radhakrishnan
@ 2015-05-21 11:10 ` Szabolcs Nagy
0 siblings, 0 replies; 4+ messages in thread
From: Szabolcs Nagy @ 2015-05-21 11:10 UTC (permalink / raw)
To: Ramana Radhakrishnan, Andrew Pinski
Cc: Ramana Radhakrishnan, gcc-patches, libstdc++
On 19/05/15 17:03, Ramana Radhakrishnan wrote:
> On Tue, May 19, 2015 at 4:54 PM, <pinskia@gmail.com> wrote:
>>> On May 19, 2015, at 5:54 AM, Ramana Radhakrishnan <ramana.radhakrishnan@foss.arm.com> wrote:
>>> Like the ARM port, the AArch64 ports needs to set glibc_integral_traps to false as integer divide instructions do not trap.
>>>
>>> Bootstrapped and regression tested on aarch64-none-linux-gnu
>>>
>>> Ok to apply ?
>>
>> Not really questioning your patch but questioning libstdc++'s defaults.
>> I wonder if this should be the default as most targets don't trap, only a few that does. And it should be safer default to say they don't trap too?
>
> How about we #error out if targets do *not* define some of these
> defaults in libstdc++ ?
__glibcxx_integral_traps seems to be used for the 'traps'
numeric_limits<T> member.
i think it can only be meaningful if LIA-1 is properly supported
(eg. div-by-zero is never optimized away) otherwise the standard
dictates UB and anything can happen. (Note that LIA-1 also requires
well-defined semantics for signed int overflow).
i don't see a way for conforming c++ code to use traps, or for
the library to guarantee either traps==true or traps==false on
any machine.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-05-19 13:04 [Patch AArch64] Add cpu_defines.h for AArch64 Ramana Radhakrishnan
2015-05-19 16:00 ` pinskia
2015-05-19 16:12 ` Ramana Radhakrishnan
2015-05-21 11:10 ` Szabolcs Nagy
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