Re: optimization/6822: GCC 3.1.1 - Internal compiler error in extract_insn, at recog.c:2132

["Eric Botcazou" <ebotcazou@libertysurf.fr>]

The following reply was made to PR optimization/6822; it has been noted by GNATS.

From: "Eric Botcazou" <ebotcazou@libertysurf.fr>
To: "Glen Nakamura" <glen@imodulo.com>
Cc: <gcc-gnats@gcc.gnu.org>,
	<gcc-bugs@gcc.gnu.org>
Subject: Re: optimization/6822: GCC 3.1.1 - Internal compiler error in extract_insn, at recog.c:2132
Date: Wed, 29 May 2002 01:29:35 +0200

 > Previously, unsigned X < 128 would be converted to unsigned X <= 127 and
 > then optimized to signed X >= 0.  After changing the order of the
 > transformations, the compiler only reduces the expression to X <= 127 ???
 > The result is the reported ICE.  This could very well be a latent bug
 > in other parts of the compiler, but it seems the change results in missed
 > opportunities to simplify expressions.  I'll post an alternative patch
 > in my next message...
 
 I was almost sure to have checked the cross-dependencies between the various
 blocks of code, but I overlooked this 'unsigned <= 0x7fffffff' thing... Your
 patch is obviously better than mine in order to fix this chicken-and-egg
 problem.
 
 May I suggest you to add thorough cross-comments to the code ? I see you did
 so for the second optimization and I think it would be nice to do it for the
 first one too (saying that the current location of the optimization causes
 the second one to be altered).
 
 It looks like this doesn't fit with the GCC policy on the matter, but it
 could also be worth leaving the original code inside an #if 0/#endif or a
 comment.
 
 --
 Eric Botcazou
 ebotcazou@multimania.com