On Tue, Jul 24, 2012 at 5:50 PM, Andrew Pinski
<andrew.pin...@caviumnetworks.com> wrote:
> Hi,
> Before tuples was introduced, VN used to lookup the simplified
> expression to see if it was available already and use that instead of
> the non simplified one. This patch adds the support back to VN to do
> exactly that.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
I think this should be done for all RHS and SSA name LHS, not only
for UNARY/BINARY/TERNARY - because even for SINGLE rhs we
can end up simplifying (for REALPART_EXPR for example which we
handle as nary, too). I think we constrain try_to_simplify enough
so that
+ /* First try to lookup the simplified expression. */
+ if (simplified && valid_gimple_rhs_p (simplified))
+ {
+ tree result = vn_nary_op_lookup (simplified, NULL);
+ if (result)
+ {
+ changed = set_ssa_val_to (lhs, result);
+ goto done;
+ }
+ changed = set_ssa_val_to (lhs, lhs);
+ vn_nary_op_insert (simplified, lhs);
+ }
switch (get_gimple_rhs_class (code))
{
case GIMPLE_UNARY_RHS:
case GIMPLE_BINARY_RHS:
...
should work. As you also insert the simplified variant I think we really
(finally) want to have a valid_nary_op routine rather than relying on
valid_gimple_rhs_p which is way too generic.
Thanks,
Richard.
> Thanks,
> Andrew Pinski
>
> ChangeLog:
>
> * tree-ssa-sccvn.c (visit_use): Look up the simplified
> expression before visting the original one.
>
> * gcc.dg/tree-ssa/ssa-fre-9.c: Update the number of
> eliminatations that happen.
