Re: [PATCH] powerpc: provide __bswapdi2

[Gabriel Paubert <paubert@iram.es>]

On Mon, May 13, 2013 at 05:09:59PM +1000, Michael Neuling wrote:
> David Woodhouse <dwmw2@infradead.org> wrote:
> 
> > From: David Woodhouse <David.Woodhouse@intel.com>
> > 
> > Some versions of GCC apparently expect this to be provided by libgcc.
> > 
> > Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
> > ---
> > Untested.
> > 
> > diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
> > index 19e096b..f077dc2 100644
> > --- a/arch/powerpc/kernel/misc_32.S
> > +++ b/arch/powerpc/kernel/misc_32.S
> > @@ -657,6 +657,17 @@ _GLOBAL(__ucmpdi2)
> >  	li	r3,2
> >  	blr
> >  
> > +_GLOBAL(__bswapdi2)
> > +	rlwinm	10,4,8,0xffffffff
> > +	rlwinm	11,3,8,0xffffffff
> > +	rlwimi	10,4,24,0,7
> > +	rlwimi	11,3,24,0,7
> > +	rlwimi	10,4,24,16,23
> > +	rlwimi	11,3,24,16,23
> > +	mr	4,11
> > +	mr	3,10
> > +	blr
> > +
> 
> This doesn't work for me but the below does:
> 
> _GLOBAL(__bswapdi2)
> 	rotlwi  r9,r4,8
> 	rotlwi  r10,r3,8
> 	rlwimi  r9,r4,24,0,7
> 	rlwimi  r10,r3,24,0,7
> 	rlwimi  r9,r4,24,16,23
> 	rlwimi  r10,r3,24,16,23
> 	mr      r4,r10
> 	mr      r3,r9
> 	blr
> 

Actually, I'd swap the two mr instructions to never
have an instruction that uses the result from the
previous one. 


> stolen from GCC -02 output of:
>   unsigned long long __bswapdi2(unsigned long long x)
>   {
> 	 return ((x & 0x00000000000000ffULL) << 56) |
> 		((x & 0x000000000000ff00ULL) << 40) |
> 		((x & 0x0000000000ff0000ULL) << 24) |
> 		((x & 0x00000000ff000000ULL) <<  8) |
> 		((x & 0x000000ff00000000ULL) >>  8) |
> 		((x & 0x0000ff0000000000ULL) >> 24) |
> 		((x & 0x00ff000000000000ULL) >> 40) |
> 		((x & 0xff00000000000000ULL) >> 56);
>   }
> 
> >  _GLOBAL(abs)
> >  	srawi	r4,r3,31
> >  	xor	r3,r3,r4
> > diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
> > index 5cfa800..3b2e6e8 100644
> > --- a/arch/powerpc/kernel/misc_64.S
> > +++ b/arch/powerpc/kernel/misc_64.S
> > @@ -234,6 +234,18 @@ _GLOBAL(__flush_dcache_icache)
> >  	isync
> >  	blr
> >  
> > +_GLOBAL(__bswapdi2)
> > +	srdi	8,3,32
> > +	rlwinm	7,3,8,0xffffffff
> > +	rlwimi	7,3,24,0,7
> > +	rlwinm	9,8,8,0xffffffff
> > +	rlwimi	7,3,24,16,23
> > +	rlwimi	9,8,24,0,7
> > +	rlwimi	9,8,24,16,23
> > +	sldi	7,7,32
> > +	or	7,7,9
> > +	mr	3,7
> > +	blr
> 
> This works but we should add "r" to the register names.
> 

And merge the last two instructions as a single "or r3,r7,r9".


	Gabriel