[Bug tree-optimization/21485] [4.2/4.3/4.4 Regression] missed load PRE, PRE makes i?86 suck

[rguenth at gcc dot gnu dot org]

------- Comment #32 from rguenth at gcc dot gnu dot org  2008-10-04 00:57 -------
As we PHI-translate k_1 * 4 we are not able to find D.1237_7 * 4 in the
SCCVN tables.  So we allocate a new value-id for it.  Oops.  This is because
once we say its type is unsigned int and once it's unsigned long.  And
we require types to be pointer-equal in the hash comparison fn.

I have a patch to fix this which makes this run even more slow.  -fno-tree-pre
fixes the speed regression.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.2/4.3/4.4 Regression]    |[4.2/4.3/4.4 Regression]
                   |missed load PRE             |missed load PRE, PRE makes
                   |                            |i?86 suck


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21485