[Bug middle-end/18574] [4.0 Regression] bootstrap comprison failed

["shebs at apple dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From shebs at apple dot com  2004-11-22 00:24 -------
Subject: Re:  [4.0 Regression] bootstrap comprison	failed

Jeffrey A Law wrote:

>I've been unable to reproduce the comparison failures.  However, as I
>outlined in an earlier message, I have come up with a scenario in which
>my patch might cause a comparison failure.
>
>
This fixes bootstrap compare failures on Darwin, thank you saving
me from the horrible debugging hell I was dreading when I saw
miscompares last night... :-)

Stan

>This patch changes the hashing routine to use block indices rather
>than hash on pointers.  That ought to stabilize the hash (and thus the
>hash table traversals and SSA_NAME coalescing) in cases where it
>was unstable before.
>
>Since I've been unable to trigger the failure here, I can't say for
>certain whether or not this patch fixes the bootstrap failures others
>have seen.
>
>FWIW, this has been bootstrapped and regression tested on
>i686-pc-linux-gnu.
>
>
>
>
>------------------------------------------------------------------------
>
>	* tree-ssa-threadupdate.c (redirection_data_hash): Use the
>	index of the destination block for the hash value rather than
>	hashing a pointer.
>
>Index: tree-ssa-threadupdate.c
>===================================================================
>RCS file: /cvs/gcc/gcc/gcc/tree-ssa-threadupdate.c,v
>retrieving revision 2.15
>diff -c -p -r2.15 tree-ssa-threadupdate.c
>*** tree-ssa-threadupdate.c	20 Nov 2004 12:48:13 -0000	2.15
>--- tree-ssa-threadupdate.c	21 Nov 2004 15:00:33 -0000
>*************** static hashval_t
>*** 203,209 ****
>  redirection_data_hash (const void *p)
>  {
>    edge e = ((struct redirection_data *)p)->outgoing_edge;
>!   return htab_hash_pointer (e);
>  }
>  
>  static int
>--- 203,209 ----
>  redirection_data_hash (const void *p)
>  {
>    edge e = ((struct redirection_data *)p)->outgoing_edge;
>!   return e->dest->index;
>  }
>  
>  static int
>



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18574