Re: optimization/8492: [3.3 regression] GCC spins forever compiling loop

[Janis Johnson <janis187@us.ibm.com>]

The following reply was made to PR optimization/8492; it has been noted by GNATS.

From: Janis Johnson <janis187@us.ibm.com>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org, gcc-bugs@gcc.gnu.org,
   nobody@gcc.gnu.org, thorpej@shagadelic.org, jh@suse.cz
Cc:  
Subject: Re: optimization/8492: [3.3 regression] GCC spins forever compiling loop
Date: Fri, 20 Dec 2002 14:51:32 -0800

 The mainline regression reported in PR optimization/8492
 (an infinite loop in the compiler) showed up starting with
 this patch:
 
 Sun Jul 21 00:54:54 CEST 2002  Jan Hubicka  <jh@suse.cz>
 
         * gcse.c: Include cselib.h
         (constptop_register): Break out from ...
         (cprop_insn): ... here; kill basic_block argument.
         (do_local_cprop, local_cprop_pass): New functions.
         (one_cprop_pass): Call local_cprop_pass.
 
 Here's a small test case that causes the compiler to hang
 when compiled on i686-linux with -O2:
 
 -------------------
 /* compiler hangs when compiling with -O2  */
 int count;
 
 int func(int *valp) {
   int val, locked = 0;
 
   while ((val = *valp) != 0) {
     if (count) {
       if (count)
         locked = 1;
       else
         locked = 1;
 
     if (!locked)
       continue;
     }
 
     if (!count)
       count--;
 
     break;
   }
 
   return val;
 }
 -------------------
 
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8492