Messages in this thread | | | Date | Mon, 20 Feb 2012 17:21:58 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCHv2 5/6] jump label: detect %c support for ARM |
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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.
> 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 '#'.
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