eba7136e7b
In order to be able to efficiently iterate backwards over instructions and removing or replacing instructions in the graph we want them to be a double-linked list inside basic blocks. The list has the following 1. Block entry instructions do not have a previous instruction. 2. The last instruction in a block may or may not have a next instruction: - Branches have a NULL-successor. - Normal block exits have a block entry instructions as successor. This CL also makes the accessor for previous and next instruction in this list non-virtual. This avoidis the current code duplication there. Review URL: https://chromiumcodereview.appspot.com//10665022 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@9297 260f80e4-7a28-3924-810f-c04153c831b5