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This occurs due to an alloca representing a separate ownership from the original pointer. Thus consider the following pseudo-IR: objc_retain(%a) for (...) { objc_retain(%a) %block <- %a F(%block) objc_release(%block) } objc_release(%a) From the perspective of the optimizer, the %block is a separate provenance from the original %a. Thus the optimizer pairs up the inner retain for %a and the outer release from %a, resulting in segfaults. This is fixed by noting that the signature of a mismatch of retain/releases inside the for loop is a Use/CanRelease top down with an None bottom up (since bottom up the Retain-CanRelease-Use-Release sequence is completed by the inner objc_retain, but top down due to the differing provenance from the objc_release said sequence is not completed). In said case in CheckForCFGHazards, we now clear the state of %a implying that no pairing will occur. Additionally a test case is included. rdar://12969722 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179747 91177308-0d34-0410-b5e6-96231b3b80d8 |
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Hello | ||
InstCombine | ||
Instrumentation | ||
IPO | ||
ObjCARC | ||
Scalar | ||
Utils | ||
Vectorize | ||
CMakeLists.txt | ||
LLVMBuild.txt | ||
Makefile |