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To: Diego Novillo <dnovillo@redhat.com>
cc: Zack Weinberg <zack@codesourcery.com>, Michael Matz <matz@suse.de>,
   "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Reply-To: law@redhat.com
Subject: Re: Dead-code elimination can't remove string copy insns? 
In-Reply-To: Your message of "Tue, 13 May 2003 13:07:22 EDT."
             <20030513170722.GA7112@tornado.toronto.redhat.com> 
From: law@redhat.com
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Date: Tue, 13 May 2003 17:38:00 -0000
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In message <20030513170722.GA7112@tornado.toronto.redhat.com>, Diego Novillo wr
ites:
 >On Tue, May 13, 2003 at 09:40:33AM -0700, Zack Weinberg wrote:
 >
 >> gcc.dg/const-elim-1.c.  On an x86, compile it with -march=i386 -O2;
 >> rs6000-ibm-aix5 and arm-elf also show the problem.
 >> 
 >Yup, tree-ssa handles it.  The original program in GIMPLE form is
 >on the left.  The optimized version is on the right (we still
 >don't linearize GOTO_EXPRs).
Does this look better? :-)

test1 ()
{       
  int retval.6;
  int T.1;
  char[37] * T.2;
  char * T.3;
  const char * T.4;
  struct S <UVda10>;
  struct S * T.5;
        
  { 
    int <UVdee0>;
        
    <ULde70>:;
  };  
  return;
}
    
    
;; Function test2 (test2)
    
test2 ()
{ 
  int retval.11;
  char[40] * T.7;
  char * T.8;
  int T.9;
  struct S * S.10;
  const char * str;
  struct S S;
  const complex double cplx;
  
  {
    int <UVc230>;
  
    <ULc1c0>:;
  };
  return;
} 
  

;; Function returns_23 (returns_23)

returns_23 ()
{ 
  return 23; 
} 


Note the GOTOs are gone :-)

The problem was the code didn't match the toplevel comments in regards
to when the pass should be repeated.  Basically we want to repeat if
we eliminated a control structure as that can in turn expose more
GOTOs that we know how to eliminate.

Testing of the fix is in progress.

jeff