[U-Boot] [RFC] ARM: prevent misaligned array inits

[Joakim Tjernlund]

Albert ARIBAUD <albert.u.boot at aribaud.net> wrote on 2012/10/02 22:05:40:
>
> Hi Joakim,
>
> On Tue, 2 Oct 2012 21:13:39 +0200, Joakim Tjernlund
> <joakim.tjernlund at transmode.se> wrote:
>
> >
> >
> > >   *********************************************************************/
> > >  void display_board_info(u32 btype)
> > >  {
> > > -   char cpu_2420[] = "2420";   /* cpu type */
> > > -   char cpu_2422[] = "2422";
> > > -   char cpu_2423[] = "2423";
> > > -   char db_men[] = "Menelaus"; /* board type */
> > > -   char db_ip[] = "IP";
> > > -   char mem_sdr[] = "mSDR";    /* memory type */
> > > -   char mem_ddr[] = "mDDR";
> > > -   char t_tst[] = "TST";       /* security level */
> > > -   char t_emu[] = "EMU";
> > > -   char t_hs[] = "HS";
> > > -   char t_gp[] = "GP";
> > > -   char unk[] = "?";
> > > +   char *cpu_2420 = "2420";   /* cpu type */
> > > +   char *cpu_2422 = "2422";
> > > +   char *cpu_2423 = "2423";
> > > +   char *db_men = "Menelaus"; /* board type */
> > > +   char *db_ip = "IP";
> > > +   char *mem_sdr = "mSDR";    /* memory type */
> > > +   char *mem_ddr = "mDDR";
> > > +   char *t_tst = "TST";       /* security level */
> > > +   char *t_emu = "EMU";
> > > +   char *t_hs = "HS";
> > > +   char *t_gp = "GP";
> > > +   char *unk = "?";
> >
> > hmm, on ppc I think this will cause relocation entries which will build size.
> >
> >  Jocke
>
> Can you try it and post results with and without it? Sizes and if
> possible disassembly of the function for both cases.

Since you asked, I had to check :)
Did this:
#include <stdio.h>
#ifdef NO_RELOC
void display_board_info1(int btype)
{
	char cpu_2420[] = "2420";   /* cpu type */
	char cpu_2422[] = "2422";
	char cpu_2423[] = "2423";
	char db_men[] = "Menelaus"; /* board type */
	char db_ip[] = "IP";
	char mem_sdr[] = "mSDR";    /* memory type */
	char mem_ddr[] = "mDDR";
	char t_tst[] = "TST";		     /* security level */
	char t_emu[] = "EMU";
	char t_hs[] = "HS";
	char t_gp[] = "GP";
	char unk[] = "?";
	printf("%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s\n",
	       cpu_2420, cpu_2422, cpu_2423, db_men, db_ip, mem_sdr,
	       mem_ddr, t_tst, t_emu, t_hs, t_gp, unk);
}
#else
void display_board_info2(int btype)
{
	char *cpu_2420 = "2420";   /* cpu type */
	char *cpu_2422 = "2422";
	char *cpu_2423 = "2423";
	char *db_men = "Menelaus"; /* board type */
	char *db_ip = "IP";
	char *mem_sdr = "mSDR";    /* memory type */
	char *mem_ddr = "mDDR";
	char *t_tst = "TST";		     /* security level */
	char *t_emu = "EMU";
	char *t_hs = "HS";
	char *t_gp = "GP";
	char *unk = "?";
	printf("%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s\n",
	       cpu_2420, cpu_2422, cpu_2423, db_men, db_ip, mem_sdr,
	       mem_ddr, t_tst, t_emu, t_hs, t_gp, unk);
}
#endif
and built it with:
powerpc-softfloat_4.5.3-linux-gnu-gcc -O2 -fpic -mrelocatable ppc-str-reloc.c -c -DNO_RELOC -o no_reloc.o

and

powerpc-softfloat_4.5.3-linux-gnu-gcc -O2 -fpic -mrelocatable ppc-str-reloc.c -c -o reloc.o

Result is:
#> size reloc.o no_reloc.o    text	   data	    bss	    dec	    hex	filename
    248	     52	      0	    300	    12c	reloc.o
    538	      0	      0	    538	    21a	no_reloc.o

Turns out that gcc still uses const string ptrs which makes for really bad code.
So your char * conversion is better for ppc too given the way gcc operates

 Jocke