Messages in this thread Patches in this message | | | Date | Wed, 22 Feb 2012 19:02:40 +0530 | From | Rabin Vincent <> | Subject | Re: [PATCHv2 5/6] jump label: detect %c support for ARM |
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On Mon, Feb 20, 2012 at 05:21:58PM +0000, Russell King - ARM Linux wrote: > On Sat, Jan 28, 2012 at 07:05:24PM +0530, Rabin Vincent wrote: > > Some versions of ARM GCC which do support asm goto, have problems > > handling the the %c specifier. Since we need the %c to support jump > > labels on ARM, detect that too in the asm goto detection script to avoid > > build errors with these versions. > > I'm not sure how this detects properly working %c support. %c support > has been rather flakey on ARM for some time, I'm not sure which version > of gcc was fixed for it.
Right, it only detects that %c on a sym+offset doesn't ICE, which was what it had been doing since atleast version 4.3.
The assumption was that since asm goto was only added in ~4.5, all older compilers (regardless of their state of %c support) would choke (as we want them to) on the existing second half of this script.
I have added the change you suggested below.
> > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637 > > > > Cc: Jason Baron <jbaron@redhat.com> > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Rabin Vincent <rabin@rab.in> > > --- > > scripts/gcc-goto.sh | 18 +++++++++++++++++- > > 1 files changed, 17 insertions(+), 1 deletions(-) > > > > diff --git a/scripts/gcc-goto.sh b/scripts/gcc-goto.sh > > index 98cffcb..9b744de 100644 > > --- a/scripts/gcc-goto.sh > > +++ b/scripts/gcc-goto.sh > > @@ -2,4 +2,20 @@ > > # Test for gcc 'asm goto' support > > # Copyright (C) 2010, Jason Baron <jbaron@redhat.com> > > > > -echo "int main(void) { entry: asm goto (\"\"::::entry); return 0; }" | $@ -x c - -c -o /dev/null >/dev/null 2>&1 && echo "y" > > +cat << "END" | $@ -x c - -c -o /dev/null >/dev/null 2>&1 && echo "y" > > +int main(void) > > +{ > > +#ifdef __arm__ > > + /* > > + * Not related to asm goto, but used by jump label > > + * and broken on some ARM GCC versions (see GCC Bug 48637). > > + */ > > + static struct { int dummy; int state; } tp; > > + asm ("@ %c0" :: "i" (&tp.state)); > > While this detects the presence of the ICE, previous compilers included > the '#' before the constant, which leads to problems. I think a better > check would be: > asm(".long %c0" :: "i" (&tp.state)); > > to make sure that it spits out something purely numeric, rather than > something prefixed with a '#'.
OK, done:
8<---------------- From f3a3bd64f72720def5cfbaedf6ff83ca54f1644b Mon Sep 17 00:00:00 2001 From: Rabin Vincent <rabin@rab.in> Date: Wed, 23 Nov 2011 20:05:09 +0530 Subject: [PATCH] jump label: detect %c support for ARM
Some versions of ARM GCC which do support asm goto, do not support the %c specifier. Since we need the %c to support jump labels on ARM, detect that too in the asm goto detection script to avoid build errors with these versions.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637 Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Rabin Vincent <rabin@rab.in> --- scripts/gcc-goto.sh | 18 +++++++++++++++++- 1 files changed, 17 insertions(+), 1 deletions(-) diff --git a/scripts/gcc-goto.sh b/scripts/gcc-goto.sh index 98cffcb..a2af2e8 100644 --- a/scripts/gcc-goto.sh +++ b/scripts/gcc-goto.sh @@ -2,4 +2,20 @@ # Test for gcc 'asm goto' support # Copyright (C) 2010, Jason Baron <jbaron@redhat.com> -echo "int main(void) { entry: asm goto (\"\"::::entry); return 0; }" | $@ -x c - -c -o /dev/null >/dev/null 2>&1 && echo "y" +cat << "END" | $@ -x c - -c -o /dev/null >/dev/null 2>&1 && echo "y" +int main(void) +{ +#ifdef __arm__ + /* + * Not related to asm goto, but used by jump label + * and broken on some ARM GCC versions (see GCC Bug 48637). + */ + static struct { int dummy; int state; } tp; + asm (".long %c0" :: "i" (&tp.state)); +#endif + +entry: + asm goto ("" :::: entry); + return 0; +} +END -- 1.7.9
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