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Date: Mon, 11 Jul 2011 14:04:00 -0000
From: Michael Matz <matz@suse.de>
To: Richard Guenther <rguenther@suse.de>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Make VRP optimize useless conversions
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Hi,

On Mon, 11 Jul 2011, Richard Guenther wrote:

> The following actually works.
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
> 
> Can you double-check it?

Seems sensible.  Given this:

  short s;
  int i;
  for (s = 0; s <= 127; s++)
    i += (signed char)(unsigned char)s;
  return i;

(or similar), does it remove the conversions to signed and unsigned char 
now?  And does it _not_ remove them if the upper bound is 128, or the 
lower bound is -1 ?

Similar (now with extensions):
  signed char c;
  unsigned u;
  for (c = 1; c < 127; c++)
    u += (unsigned)(int)c;

The conversion to int is not necessary; but it is when the lower bound 
is -1.


Ciao,
Michael.