linux-kernel - Re: [PATCH] math-emu/setcc: avoid gcc extension

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Message-Id: <20070107130726.96973116.randy.dunlap@oracle.com>
Date:	Sun, 7 Jan 2007 13:07:26 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Segher Boessenkool <segher@...nel.crashing.org>,
	akpm <akpm@...l.org>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] math-emu/setcc: avoid gcc extension

On Sun, 7 Jan 2007 19:58:45 +0000 Christoph Hellwig wrote:

> On Sun, Jan 07, 2007 at 11:19:00AM -0800, Randy Dunlap wrote:
> > On Sun, 7 Jan 2007 20:12:42 +0100 Segher Boessenkool wrote:
> > 
> > > There's an extra tab in that last line.  Could you also
> > > please fix the indenting (use a tab, not spaces) -- I know
> > > it was there originally, but since there are only a few
> > > lines in that file like that...  :-)
> > 
> > how's this one?
> > ---
> > From: Randy Dunlap <randy.dunlap@...cle.com>
> > 
> > setcc() in math-emu is written as a gcc extension statement expression
> > macro that returns a value.  However, it's not used that way and it's
> > not needed like that, so just make it a do-while non-extension macro
> > so that we don't use an extension when it's not needed.
> > 
> > Signed-off-by: Randy Dunlap <randy.dunlap@...cle.com>
> > ---
> >  arch/i386/math-emu/status_w.h        |    5 +++--
> > 
> > ---
> >  arch/i386/math-emu/status_w.h |    7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > --- linux-2620-rc2.orig/arch/i386/math-emu/status_w.h
> > +++ linux-2620-rc2/arch/i386/math-emu/status_w.h
> > @@ -48,9 +48,10 @@
> >  
> >  #define status_word() \
> >    ((partial_status & ~SW_Top & 0xffff) | ((top << SW_Top_Shift) & SW_Top))
> > -#define setcc(cc) ({ \
> > -  partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3); \
> > -  partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3); })
> > +#define setcc(cc) do { \
> > +	partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3); \
> > +	partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3); \
> > +} while (0)
> 
> Is there any reason you this shouldn't be an inline function?

That would be OK in theory, so I just tried it.

I don't get the same object files produced with an inline function
(for arch/i386/math-emu/fpu_etc.o), so I don't feel that it's quite
as safe without digging deeping into the .o file and its changes.

The 3 other .o files that use setcc() were the same when using
the inline patch version.

---
From: Randy Dunlap <randy.dunlap@...cle.com>

setcc() in math-emu is written as a gcc extension statement expression
macro that returns a value.  However, it's not used that way and it's
not needed like that, so just make it a do-while non-extension macro
so that we don't use an extension when it's not needed.

Signed-off-by: Randy Dunlap <randy.dunlap@...cle.com>
---
 arch/i386/math-emu/status_w.h        |    5 +++--

---
 arch/i386/math-emu/status_w.h |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- linux-2620-rc2.orig/arch/i386/math-emu/status_w.h
+++ linux-2620-rc2/arch/i386/math-emu/status_w.h
@@ -48,9 +48,11 @@
 
 #define status_word() \
   ((partial_status & ~SW_Top & 0xffff) | ((top << SW_Top_Shift) & SW_Top))
-#define setcc(cc) ({ \
-  partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3); \
-  partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3); })
+static inline void setcc(int cc)
+{
+	partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3);
+	partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3);
+}
 
 #ifdef PECULIAR_486
    /* Default, this conveys no information, but an 80486 does it. */
-
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