Re: [PATCH] Use -fno-unit-at-a-time if gcc supports it

[Andreas Jaeger <aj@suse.de>]

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Robert Love <rml@tech9.net> writes:

> On Fri, 2003-09-05 at 11:17, Andreas Jaeger wrote:
>
>
>> Since unit-at-a-time has better inlining heuristics the better way is
>> to add the used attribute - but that takes some time.  The short-term
>> solution would be to add the compiler flag,
>
> Won't we get a linker error if a static symbol is used but
> optimized-away?  It shouldn't be hard to fix the n linker errors that
> crop up.

Yes, we would get a linker error.

> And why are we using static symbols in inline assembly outside of the
> compilation scope?

Don't know.

> Anyhow, if it generates an error, this isn't hard to fix.

Just lots of places...

> Here is the start...
>
> 	Robert Love
>
>
> --- linux-rml/include/linux/compiler.h	Fri Sep  5 11:57:56 2003
> +++ linux/include/linux/compiler.h	Fri Sep  5 12:02:02 2003
> @@ -74,6 +74,19 @@
>  #define __attribute_pure__	/* unimplemented */
>  #endif
>  
> +/*
> + * As of gcc 3.2, we can mark a function as 'used' and gcc will assume that,
> + * even if it does not find a reference to it in any compilation unit.  We
> + * need this for gcc 3.4 and beyond, which can optimize on a program-wide
> + * scope, and not just one file at a time, to avoid static symbols being
> + * discarded.
> + */
> +#if (__GNUC__ == 3 && __GNUC_MINOR__ > 1) || __GNUC__ > 3
> +#define __attribute_used__	__attribute__((used))
> +#else
> +#define __attribute_used__	/* unimplemented */

In glibc we have for the else case:
# define __attribute_used__ __attribute__ ((__unused__))

This might reduce warnings about unused functions.  But this change is
not critical IMO, so your patch looks fine!

> +#endif
> +
>  /* This macro obfuscates arithmetic on a variable address so that gcc
>     shouldn't recognize the original var, and make assumptions about it */
>  #define RELOC_HIDE(ptr, off)					\

Andreas
-- 
 Andreas Jaeger, aj@suse.de, http://www.suse.de/~aj
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