[U-Boot] [PATCH 7/7] GCC4.6: Squash warning in cmd_mem.c

[Marek Vasut]

On Monday, September 26, 2011 09:01:16 PM Simon Glass wrote:
> Hi Marek,
> 
> On Mon, Sep 26, 2011 at 11:34 AM, Marek Vasut <marek.vasut at gmail.com> wrote:
> > On Monday, September 26, 2011 08:29:22 PM Simon Glass wrote:
> >> Hi Merek,
> >> 
> >> On Mon, Sep 26, 2011 at 11:24 AM, Marek Vasut <marek.vasut at gmail.com> 
wrote:
> >> > On Monday, September 26, 2011 08:05:43 PM Simon Glass wrote:
> >> >> Hi Marek,
> >> >> 
> >> >> On Sun, Sep 25, 2011 at 5:26 PM, Marek Vasut <marek.vasut at gmail.com> 
wrote:
> >> >> > cmd_mem.c: In function ‘do_mem_loop’:
> >> >> > cmd_mem.c:474:25: warning: variable ‘junk’ set but not used
> >> >> > [-Wunused-but-set-variable]
> >> >> > 
> >> >> > The assigned variable can be removed because the pointers are
> >> >> > volatile so accesses to their addresses are always generated.
> >> >> > 
> >> >> > Signed-off-by: Marek Vasut <marek.vasut at gmail.com>
> >> >> > ---
> >> >> >  common/cmd_mem.c |    8 ++++----
> >> >> >  1 files changed, 4 insertions(+), 4 deletions(-)
> >> >> > 
> >> >> > diff --git a/common/cmd_mem.c b/common/cmd_mem.c
> >> >> > index 4daa1b3..e84cc4e 100644
> >> >> > --- a/common/cmd_mem.c
> >> >> > +++ b/common/cmd_mem.c
> >> >> > @@ -471,7 +471,7 @@ int do_mem_base (cmd_tbl_t *cmdtp, int flag,
> >> >> > int argc, char * const argv[])
> >> >> > 
> >> >> >  int do_mem_loop (cmd_tbl_t *cmdtp, int flag, int argc, char *
> >> >> > const argv[]) {
> >> >> > -       ulong   addr, length, i, junk;
> >> >> > +       ulong   addr, length, i;
> >> >> >        int     size;
> >> >> >        volatile uint   *longp;
> >> >> >        volatile ushort *shortp;
> >> >> > @@ -518,7 +518,7 @@ int do_mem_loop (cmd_tbl_t *cmdtp, int flag,
> >> >> > int argc, char * const argv[]) longp = (uint *)addr;
> >> >> >                        i = length;
> >> >> >                        while (i-- > 0)
> >> >> > -                               junk = *longp++;
> >> >> > +                               *longp++;
> >> >> >                }
> >> >> >        }
> >> >> >        if (size == 2) {
> >> >> > @@ -526,14 +526,14 @@ int do_mem_loop (cmd_tbl_t *cmdtp, int flag,
> >> >> > int argc, char * const argv[]) shortp = (ushort *)addr;
> >> >> >                        i = length;
> >> >> >                        while (i-- > 0)
> >> >> > -                               junk = *shortp++;
> >> >> > +                               *shortp++;
> >> >> >                }
> >> >> >        }
> >> >> >        for (;;) {
> >> >> >                cp = (u_char *)addr;
> >> >> >                i = length;
> >> >> >                while (i-- > 0)
> >> >> > -                       junk = *cp++;
> >> >> > +                       *cp++;
> >> >> >        }
> >> >> >  }
> >> >> 
> >> >> I checked the ARM assembler output and it looks fine.
> >> >> 
> >> >> Acked-by: Simon Glass <sjg at chromium.org>
> >> >> 
> >> >> Re the 'length == 1' case (above your patch) site, it is assigning to
> >> >> 'i' here. Could/should we remove that assignment also?
> >> > 
> >> > The loop below depends on that ... ?
> >> 
> >> Which loop? It doesn't look like the value of i is used?
> > 
> > i = length;
> > while (i-- > 0)
> > 
> > This loop
> 
> The assignment to i I was referring to is here:
> 
> 	if (length == 1) {
> 		if (size == 4) {
> 			longp = (uint *)addr;
> 			for (;;)
> 				i = *longp;
>                               ^^^ this line
> 
> 		}
> 		if (size == 2) {
> 			shortp = (ushort *)addr;
> 			for (;;)
> 				i = *shortp;
>                               ^^^ this line
> 
> 		}
> 		cp = (u_char *)addr;
> 		for (;;)
> 			i = *cp;
>                               ^^^ this line
> 
> 	}
> 
> I was wondering if we need to assign to i? The output code appears
> unchanged with my compiler if the 'i =' is removed.

Oh, right ... this can be removed. That code seems quite legacy and in a urgent 
need of cleanup. Shall we wrap this change into this patch or do a subsequent 
one ?

Cheers
> 
> Regards,
> Simon