[CodeExtractor] Update function's assumption cache after extracting blocks from it

Summary: Assumption cache's self-updating mechanism does not correctly handle the case when blocks are extracted from the function by the CodeExtractor. As a result function's assumption cache may have stale references to the llvm.assume calls that were moved to the outlined function. This patch fixes this problem by removing extracted llvm.assume calls from the function’s assumption cache.

Reviewers: hfinkel, vsk, fhahn, davidxl, sanjoy

Reviewed By: hfinkel, vsk

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57215

llvm-svn: 353500