Transform : Add opt for src=tgt

[abhilash1910]

Adds in the optimization to rewrite "tgt /\ (src -> foo)" to "tgt /\ foo" if src=tgt .
Tested against existing and newer opt.ll cases.
@regehr @nunoplopes please help to review, thanks.

[nunoplopes]

I don't understand this patch. It removes the existing optimization despite claiming it adds a new optimization

[abhilash1910]

@nunoplopes , yes this aims to target the commented opt path where src = tgt. For src!=tgt the default opt path is taken (in else). Initially I only did pre_tgt = pre_tgt_and() inside the if() to make it tgt ^foo, but this did not look after pre_src, hence added it . Could you help to suggest on a better way to add it ? Thanks.

[nunoplopes]

Does this give any perf benefit?

[abhilash1910]

I am checking on this for perf enhancements. Will report here , thanks