Fix some dce issues
commit58d95eabd223dd54e423b36c8576c3f88bc9862e
authorMark Williams <mwilliams@fb.com>
Sat, 11 Feb 2017 23:14:24 +0000 (11 15:14 -0800)
committerHhvm Bot <hhvm-bot@users.noreply.github.com>
Sat, 11 Feb 2017 23:27:42 +0000 (11 15:27 -0800)
tree54e3f9b87d2270cf353ef19df5b4b353130073c3
parent4dc08a9daa1cfcad74e0d5236179176ba6242f60
Fix some dce issues

Summary:
- it didn't know that destroying a Vec or Dict could run destructors
 - it thought that empty arrays could run destructors
 - it missed a few simple sequences that can be removed:

     NewMixedArray
     PopC

     etc

Reviewed By: ricklavoie

Differential Revision: D4546713

fbshipit-source-id: 047f1461b9da74dc111b6f10c85ab061ee72a835
hphp/hhbbc/dce.cpp