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 <[email protected]>
> Cc: [email protected]
> Signed-off-by: Rabin Vincent <[email protected]>
> ---
> 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 <[email protected]>
>
> -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 '#'.
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 <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Rabin Vincent <[email protected]>
> > ---
> > 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 <[email protected]>
> >
> > -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 <[email protected]>
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 <[email protected]>
Signed-off-by: Rabin Vincent <[email protected]>
---
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 <[email protected]>
-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