RE: Regression [v850,mep...]: sign_extend in loop breaks zero-overhead loop generation

[Paulo Matos <pmatos@broadcom.com>]

> -----Original Message-----
> From: Andreas Schwab [mailto:schwab@linux-m68k.org]
> Sent: 30 January 2014 14:29
> To: Paulo Matos
> Cc: gcc@gcc.gnu.org
> Subject: Re: Regression [v850,mep...]: sign_extend in loop breaks zero-overhead
> loop generation
> 
> Paulo Matos <pmatos@broadcom.com> writes:
> 
> > void
> > foo (short blockSize)
> > {
> >   short i;
> >   unsigned short loopCount;
> >
> >   loopCount = (unsigned short) (blockSize + delayLength) % 8;
> >   for (i = 0; i < loopCount; i++)
> >       *temp_ptr++ = x ^ *temp_ptr++;
> > }
> 
> You know that this is undefined code?
>

Correct, my apologies. I didn't notice the undefined behaviour that the reducer introduced in the original code.
However, the issue persists.
If instead I write:
void
foo (short blockSize)
{
  short i;
  unsigned short loopCount;
  loopCount = (unsigned short) (blockSize + delayLength) % 8;
  for (i = 0; i < loopCount; i++)
      *temp_ptr++ = x ^ *temp_ptr;
}

the sign extend is still generated from the referenced commit and persists until trunk. This causes the zero overhead loop not to be generated.

Thanks,

Paulo Matos
 
> Andreas.
> 
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."