[alsa-devel] [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod
nico at fluxnic.net
Wed Apr 27 19:10:46 CEST 2011
On Wed, 27 Apr 2011, Barry Song wrote:
> 2011/4/27 Stephen Warren <swarren at nvidia.com>:
> > Barry Song wrote at Wednesday, April 27, 2011 1:28 AM:
> >> The newest compiliers can optimize pll calculation in several codecs into
> >> __aeabi__uldivmod which doesn't exist in kernel.
> >> Then the link will fail:
> >> ERROR: "__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8974.ko] undefined!
> >> ERROR: "__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8940.ko] undefined!
> >> ERROR: "__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8510.ko] undefined!
> >> This patch prevent the optimizaton by insert ASM.
> > Aren't there compiler flags that tell gcc it isn't operating in a hosted(?)
> > environment, and hence not to emit calls to these functions? If so, I
> > imagine they should be added to the kernel's core (or ARM arch ) makefiles.
> > I doubt __aeabi_uldivmod is the only function of this type. How was this
> > solved for other such functions; does the kernel implement the AEABI
> > functions, and this implementation is simply missing?
> __aeabi_uldivmod is not implemented by kernel, others are implemented
> in arch/arm/lib/lib1funcs.S:
> extern void __aeabi_idiv(void);
> extern void __aeabi_idivmod(void);
> extern void __aeabi_lasr(void);
> extern void __aeabi_llsl(void);
> extern void __aeabi_llsr(void);
> extern void __aeabi_lmul(void);
> extern void __aeabi_uidiv(void);
> extern void __aeabi_uidivmod(void);
> extern void __aeabi_ulcmp(void);
This is not the point. uldivmod will not be implemented on purpose
because this is a kernel policy _not_ to create any code that would
And the description above is wrong too. It's not about "the newest
compiler can optimize ..." but rather "the newest compiler has a bug
that leave a stray reference to __aeabi_uldivmod in the compiled
object." As far as I'm concerned, the code is fine as is. It is the
compiler that is wrong.
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