RE: [avr-gcc-list] Multiply improvement [1]

[Weddington, Eric]

Hmm. Then if it is that rare, then I'm thinking that it might be ok to
put it into a release at the last minute. As you said, the patch is
obvious, and these types of operations are rare. I am open to others'
suggestions.

I'm curious though: Mike got CSiBE to run for the AVR? Can Mike post
documentation on how to do this?

Eric 

> -----Original Message-----
> From: Anatoly Sokolov [mailto:address@hidden 
> Sent: Sunday, April 27, 2008 1:55 PM
> To: Weddington, Eric; avr-GCC
> Subject: Re: [avr-gcc-list] Multiply improvement [1]
> 
> Hi.
> 
> Patch is obvious and and I hope is true. 
> 
> Mike run gcc-testsuite with this patch:
> "There are no new FAILs or PASSes!"
> 
> But:
> "Hm, a short CSiBE-run showed no change in code size. :-/"
> On my testsets also no change in code size.
> 
> So signed on unsigned chars multiplication is very rare 
> operation in tests.
> 
> I to wait month for user responses before to add the patch in 
> the GCC. 
> 
> Take the decision themselves.
> 
> Anatoly.
> 
> ----- Original Message ----- 
> From: "Weddington, Eric" <address@hidden>
> To: "Anatoly Sokolov" <address@hidden>; "avr-GCC" 
> <address@hidden>
> Sent: Sunday, April 27, 2008 11:11 PM
> Subject: RE: [avr-gcc-list] Multiply improvement [1]
> 
> 
> Hi Anatoly,
> 
> Thanks for the patch!
> 
> Do you think that this patch is ok to put into the next 
> WinAVR release?
> 
> Eric 
> 
> > -----Original Message-----
> > From: 
> > address@hidden 
> > [mailto:address@hidden
> > org] On Behalf Of Anatoly Sokolov
> > Sent: Sunday, April 27, 2008 11:47 AM
> > To: avr-GCC
> > Subject: [avr-gcc-list] Multiply improvement [1]
> > 
> > Hello.
> > 
> > Now AVR-GCC for multiplication of two unsigned and two signed char 
> > operands uses instructions 'MUL' and 'MULS' accordingly and is 
> > 8x8=16bits operation. Multiplication signed on unsigned chars 
> > is carried 
> > out  as multiplication of two 16-bit values, though in AVR 
> core there 
> > is instruction MULSU. This patch adds a pattern usmulqihi3 for use 
> > of instruction MULSU.
> > 
> > Testcase:
> > extern unsigned char _a;
> > extern          char _b;
> > volatile extern          int _r;
> > 
> > int
> > main (void) 
> > {
> >   _r = (unsigned int)_a * (int)_b;
> >   return 0;
> > }
> > 
> > Now:
> >  lds r24,_b 
> > 
> >  clr r25  ;  6 extendqihi2/1 [length = 3]
> >  sbrc r24,7
> >  com r25
> > 
> >  lds r18,_a  ;  7 *movqi/4 [length = 2]
> > 
> >  ldi r19,lo8(0)  ;  28 *movqi/2 [length = 1]
> > 
> >  movw r20,r24  ;  26 *movhi/1 [length = 1]
> > 
> >  mul r20,r18  ;  9 *mulhi3_enh [length = 7]
> >  movw r24,r0
> >  mul r20,r19
> >  add r25,r0
> >  mul r21,r18
> >  add r25,r0
> >  clr r1
> > 
> >  sts (_r)+1,r25  ;  10 *movhi/3 [length = 4]
> >  sts _r,r24
> > 
> > 
> > With patch:
> >  lds r18,_a  ;  5 *movqi/4 [length = 2]
> > 
> >  lds r20,_b  ;  6 *movqi/4 [length = 2]
> > 
> >  mulsu r20,r18  ;  7 usmulqihi3 [length = 3]
> >  movw r18,r0
> >  clr r1
> > 
> >  sts (_r)+1,r19  ;  8 *movhi/3 [length = 4]
> >  sts _r,r18
> > 
> > Anatoly.
> > 
>