I guess it eliminates the dead code. Try to use the getc, putc functions,
it will not be eliminated then.
On Tue, 21 Sep 2004, lapo wrote:
> Alle 14:10, mercoledì 15 settembre 2004, lapo.pasqui@xxxxxxxx ha scritto:
> Does anybody like to answer this question?
> I'd rather prefer not to open an insane bug against the gcc.
> Thanks
> Lapo
> > Hi all,
> > I've upgraded my cross gcc compiler from version 3.3.1 to 3.4.1 and I've
> > noticed a few unresolved symbols on a project (u-boot) used to compile
> > without any problem. After a quick investigation I've noticed the
> > optimization flag -0s caused a few functions not to be in the .o files.
> > Here's a code that reproduces the problem
> >
> > unsigned long get_version(void);
> > int getc(void);
> > int tstc(void);
> > void putc(const char);
> >
> > void app_startup(char **);
> >
> > enum {
> > XF_get_version ,
> > XF_getc ,
> > XF_tstc ,
> > XF_putc ,
> > XF_MAX
> > };
> >
> > typedef unsigned int size_t;
> > typedef struct global_data
> > {
> > void **jt;
> > } gd_t;
> >
> > static void __attribute__((unused)) dummy(void)
> > {
> > asm volatile ( " .globl " "get_version" "\n" "get_version" ":\n" "
> > lwz %%r11, %0(%%r29)\n" " lwz %%r11, %1(%%r11)\n" " mtctr
> > %%r11\n" " bctr\n" : : "i"(((size_t) &((gd_t *)0)->jt)),
> > "i"(XF_get_version * sizeof(void *)) : "r11"); asm volatile ( "
> > .globl " "getc" "\n" "getc" ":\n" " lwz %%r11, %0(%%r29)\n" " lwz
> > %%r11, %1(%%r11)\n" " mtctr %%r11\n" " bctr\n" : :
> > "i"(((size_t) &((gd_t *)0)->jt)), "i"(XF_getc * sizeof(void *)) : "r11");
> > asm volatile ( " .globl " "tstc" "\n" "tstc" ":\n" " lwz
> > %%r11, %0(%%r29)\n" " lwz %%r11, %1(%%r11)\n" " mtctr %%r11\n" "
> > bctr\n" : : "i"(((size_t) &((gd_t *)0)->jt)), "i"(XF_tstc * sizeof(void
> > *)) : "r11"); asm volatile ( " .globl " "putc" "\n" "putc" ":\n" "
> > lwz %%r11, %0(%%r29)\n" " lwz %%r11, %1(%%r11)\n" " mtctr
> > %%r11\n" " bctr\n" : : "i"(((size_t) &((gd_t *)0)->jt)), "i"(XF_putc *
> > sizeof(void *)) : "r11"); }
> >
> > extern unsigned long __bss_start, _end;
> >
> > void app_startup(char **argv)
> > {
> > unsigned long * cp = &__bss_start;
> > while (cp < &_end) {
> > *cp++ = 0;
> > }
> >
> > }
> >
> > Compiling it with optimization less then 2 (e.g. powerpc-linux-gcc stubs.i
> > -c -O1), I get this symbols
> >
> > nm -C --defined-only stub.o
> >
> > 00000044 T app_startup
> > 00000000 t dummy
> > 00000010 T getc
> > 00000000 T get_version
> > 00000030 T putc
> > 00000020 T tstc
> >
> >
> > Instead, using a different optimization (e.g. powerpc-linux-gcc stubs.i -c
> > -O2), I get this symbols
> >
> > nm -C --defined-only stub.o
> > 00000000 T app_startup
> >
> > Using a previous version of gcc, I've not this different behaviour
> >
> > My questions are (as I'm not am assembler guru):
> >
> > Can you see anything wrong on this code that some new feature of the gcc
> > try to overcome? Is it indeed a regression of gcc 3.4.1
> >
> >
> >
> >
> > -------------------------------------------------
> > WebMail Tele2 http://www.tele2.it
> > -------------------------------------------------
>
