On Wed, Jul 8, 2015 at 4:46 PM, Ajit Kumar Agarwal
<ajit.kumar.agar...@xilinx.com> wrote:
> All:
>
> While/For ( condition1)
> {
> Some code here.
> If(condition2 )
> continue;
> Some code here.
> }
>
> Fig(1)
>
> For the above loop in Fig(1) there will be two backedges and multiple
> latches. The below code can be transformed to the below in order to
> have a single backedge.
>
> While/For (condition1)
> {
> Some code here.
> If( condition2)
> Goto latch;
> Some code here.
>
> Latch:
> }
>
> Fig(2).
>
> With the transformation shown in Fig(2) the presence of GoTo inside loops
> affect and disables many optimizations. To enable
> the loops in Fig(1) can also be transformed to multiple loops with each
> backedge that will make the affected optimizations enabled
> and the transformed Multiple loops will enable many optimizations that are
> disabled with the presence of GoTo in Fig(2) and multiple
> latches given in Fig(1).
This is what GCC performs when doing loop_optimizer_init without
LOOPS_MAY_HAVE_MULTIPLE_LATCHES, it will
disambiguate the loop into a nested loop. We don't have a way to
force a single latch with the goto idea (which might
be useful in some cases as well, for example if the result can be
trivially if-converted).
Richard.
> Thoughts?
>
> Thanks & Regards
> Ajit
>
