Add an InterferenceCache class for caching per-block interference ranges.

When the greedy register allocator is splitting multiple global live ranges, it
tends to look at the same interference data many times. The InterferenceCache
class caches queries for unaltered LiveIntervalUnions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128764 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CMakeLists.txt

@@ -19,6 +19,7 @@ add_llvm_library(LLVMCodeGen
   GCStrategy.cpp
   IfConversion.cpp
   InlineSpiller.cpp
+  InterferenceCache.cpp
   IntrinsicLowering.cpp
   LLVMTargetMachine.cpp
   LatencyPriorityQueue.cpp