[LV] Refactor ILV to provide vectorizeInstruction(); NFC

Refactoring InnerLoopVectorizer's vectorizeBlockInLoop() to provide
vectorizeInstruction(). Aligning DeadInstructions with its only user.
Facilitates driving the transformation by VPlan - follows
https://reviews.llvm.org/D28975 and its tentative breakdown.

Differential Revision: https://reviews.llvm.org/D31997


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300183 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed