Re: [Patch AArch64] Add cpu_defines.h for AArch64.
On 19/05/15 17:03, Ramana Radhakrishnan wrote: On Tue, May 19, 2015 at 4:54 PM, pins...@gmail.com wrote: On May 19, 2015, at 5:54 AM, Ramana Radhakrishnan ramana.radhakrish...@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_limitsT 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.
[Patch AArch64] Add cpu_defines.h for AArch64.
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.radhakrish...@arm.com
* configure.host: Define cpu_defines_dir for AArch64
* config/cpu/aarch64/cpu_defines.h: New file.
From 1e38b2a848a313e5b98494094b198b7a1e34c59c Mon Sep 17 00:00:00 2001
From: Ramana Radhakrishnan ramana.radhakrish...@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 000..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
Re: [Patch AArch64] Add cpu_defines.h for AArch64.
On May 19, 2015, at 5:54 AM, Ramana Radhakrishnan ramana.radhakrish...@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.radhakrish...@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
Re: [Patch AArch64] Add cpu_defines.h for AArch64.
On Tue, May 19, 2015 at 4:54 PM, pins...@gmail.com wrote: On May 19, 2015, at 5:54 AM, Ramana Radhakrishnan ramana.radhakrish...@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.radhakrish...@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
