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The RCIdentity root ("Reference Count Identity Root") of a value V is a dominating value U for which retaining or releasing U is equivalent to retaining or releasing V. In other words, ARC operations on V are equivalent to ARC operations on U. This is a useful property to ascertain since we can use this in the ARC optimizer to make it easier to match up ARC operations by always mapping ARC operations to RCIdentityRoots instead of pointers themselves. Then we perform pairing of retains, releases which are applied to the same RCIdentityRoot. In general, the two ways that we see RCIdentical values in ObjC are via: 1. PointerCasts 2. Forwarding Calls that return their argument verbatim. As such in ObjC, two RCIdentical pointers must always point to the same memory location. Previously this concept was implicit in the code and various methods that dealt with this concept were given functional names that did not conform to any name in the "ARC" model. This often times resulted in code that was hard for the non-ARC acquanted to understand resulting in unhappiness and confusion. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229796 91177308-0d34-0410-b5e6-96231b3b80d8 |
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Hello | ||
InstCombine | ||
Instrumentation | ||
IPO | ||
ObjCARC | ||
Scalar | ||
Utils | ||
Vectorize | ||
CMakeLists.txt | ||
LLVMBuild.txt | ||
Makefile |