RE: [PATCH v4 04/12] btrace: Use function segment index in call iterator.

["Wiederhake, Tim" <tim dot wiederhake at intel dot com>]

Hi Markus,

Thanks for your input!

> -----Original Message-----
> From: Metzger, Markus T
> Sent: Thursday, May 11, 2017 12:03 PM
> To: Wiederhake, Tim <tim.wiederhake@intel.com>; gdb-patches@sourceware.org
> Cc: simon.marchi@polymtl.ca
> Subject: RE: [PATCH v4 04/12] btrace: Use function segment index in call
> iterator.
> 
> Hello Tim,
> 
> >  /* See btrace.h.  */
> > @@ -2702,26 +2684,14 @@ btrace_find_call_by_number (struct
> > btrace_call_iterator *it,
> >  			    const struct btrace_thread_info *btinfo,
> >  			    unsigned int number)
> >  {
> > -  const struct btrace_function *bfun;
> > +  const unsigned int length = btinfo->functions.size ();
> >
> > -  for (bfun = btinfo->end; bfun != NULL; bfun = bfun->flow.prev)
> > -    {
> > -      unsigned int bnum;
> > -
> > -      bnum = bfun->number;
> > -      if (number == bnum)
> > -	{
> > -	  it->btinfo = btinfo;
> > -	  it->function = bfun;
> > -	  return 1;
> > -	}
> > -
> > -      /* Functions are ordered and numbered consecutively.  We could
> bail out
> > -	 earlier.  On the other hand, it is very unlikely that we search for
> > -	 a nonexistent function.  */
> > -  }
> > +  if ((number == 0) || (number > length))
> > +    return 0;
> >
> > -  return 0;
> > +  it->btinfo = btinfo;
> > +  it->index = number - 1;
> > +  return 1;
> >  }
> 
> We have those +1 and -1 operations throughout the code.  Should we
> introduce
> some small helpers to document what we're doing?  E.g.
> 
> static inline unsigned int btrace_call_number_from_index (unsigned int
> call_index)
> {
>   return call_index + 1;
> }
> 
> and
> 
> static inline unsigned int btrace_call_number_to_index (unsigned int
> call_number)
> {
>   return call_number - 1;
> }
> 

Most of these manual adjustments are temporary and are replaced in later patches in this series. I replaced the remaining adjustments in record-btrace.c with calls to find_call_by_number which leaves us with only three occurrences in btrace.c, where we actually write to btrace_call_iterator.

> Regards,
> Markus.

Tim
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