tree if convert pass control

[Xinliang David Li <davidxl at google dot com>]

tree if conversion is an enabler pass for vectorization, so by
default, it is only turned on when vectorization is on, but may also
depend on the optimization level. Currently, the logic to handle this
is in the gate function which become hard to understand and extend.

The proposed patch move the logic from the gate function to
'finish_option' which is much clearer. The downside of this patch is
that function specific optimization node needs to be created for some
cases during omp-lowering.

Comments?


thanks,

David

Attachment: tree_if_cvt_opt.txt
Description: Text document