[Bug tree-optimization/31169] Bootstrap comparison error at revision 122821

["dave at hiauly1 dot hia dot nrc dot ca" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #22 from dave at hiauly1 dot hia dot nrc dot ca  2007-03-17 18:03 -------
Subject: Re:  Bootstrap comparison error at revision 122821

> I'll recheck with the third hunk.
j_5: [0, 12048173]  EQUIVALENCES: { } (0 elements)

There isn't any difference in the code generated with and without
the third hunk.  Also, stage1 through stage3 with hunk generate the
same code at -O2.  As far as I can tell, the code is correct in all
cases.

> > If the count is actually zero, we can end up doing x << 0 (a left shift of
> > zero).  Does hppa handle this correctly?  Does it, for

> The hardware doesn't support a left shift of zero, so at the moment
> the expanders and patterns require that the shift length be greater
> than zero.

Sorry, the above statement is wrong.  What the hardware doesn't support
is zero length deposits.  Deposit instructions are used for shifts.
In the case of an ashift with a CONST_INT shift amount x, the deposit
length is 32 - (INTVAL (x) & 31).  So, the deposit length is [1, 32].

Dave


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31169