llvm-6502/lib/Transforms/ObjCARC
Michael Gottesman acfb3584c5 [objc-arc-opts] In the presense of an alloca unconditionally remove RR pairs if and only if we are both KnownSafeBU/KnownSafeTD rather than just either or.
In the presense of a block being initialized, the frontend will emit the
objc_retain on the original pointer and the release on the pointer loaded from
the alloca. The optimizer will through the provenance analysis realize that the
two are related (albiet different), but since we only require KnownSafe in one
direction, will match the inner retain on the original pointer with the guard
release on the original pointer. This is fixed by ensuring that in the presense
of allocas we only unconditionally remove pointers if both our retain and our
release are KnownSafe (i.e. we are KnownSafe in both directions) since we must
deal with the possibility that the frontend will emit what (to the optimizer)
appears to be unbalanced retain/releases.

An example of the miscompile is:

  %A = alloca
  retain(%x)
  retain(%x) <--- Inner Retain
  store %x, %A
  %y = load %A
  ... DO STUFF ...
  release(%y)
  call void @use(%x)
  release(%x) <--- Guarding Release

getting optimized to:

  %A = alloca
  retain(%x)
  store %x, %A
  %y = load %A
  ... DO STUFF ...
  release(%y)
  call void @use(%x)

rdar://13750319

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181743 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-13 23:49:42 +00:00
..
CMakeLists.txt Extracted ObjCARCContract from ObjCARCOpts into its own file. 2013-01-29 03:03:03 +00:00
DependencyAnalysis.cpp Kill every call to @clang.arc.use in the ARC contract phase. 2013-03-22 21:38:36 +00:00
DependencyAnalysis.h Extracted ObjCARCContract from ObjCARCOpts into its own file. 2013-01-29 03:03:03 +00:00
LLVMBuild.txt Added missing dashes from header declaration comment. 2013-01-29 04:53:55 +00:00
Makefile Extracted ObjCARC.cpp into its own library libLLVMObjCARCOpts in preparation for refactoring the ARC Optimizer. 2013-01-28 01:35:51 +00:00
ObjCARC.cpp This patch breaks up Wrap.h so that it does not have to include all of 2013-05-01 20:59:00 +00:00
ObjCARC.h Add clang.arc.used to ModuleHasARC so ARC always runs if said call is present in a module. 2013-03-29 21:15:23 +00:00
ObjCARCAliasAnalysis.cpp Sorted includes using utils/sort_includes. 2013-01-29 04:20:52 +00:00
ObjCARCAliasAnalysis.h Added two missing headers from ObjCARCAliasAnalysis.h. 2013-01-29 04:09:24 +00:00
ObjCARCAPElim.cpp Hopefully fix the Windows build failure introduced in r173769 2013-01-29 09:09:27 +00:00
ObjCARCContract.cpp [objc-arc] Apply the RV optimization to retains next to calls in ObjCARCContract instead of ObjCARCOpts. 2013-04-29 06:53:53 +00:00
ObjCARCExpand.cpp Sorted includes using utils/sort_includes. 2013-01-29 04:20:52 +00:00
ObjCARCOpts.cpp [objc-arc-opts] In the presense of an alloca unconditionally remove RR pairs if and only if we are both KnownSafeBU/KnownSafeTD rather than just either or. 2013-05-13 23:49:42 +00:00
ObjCARCUtil.cpp [ObjCARC Annotations] Added support for displaying the state of pointers at the bottom/top of BBs of the ARC dataflow analysis for both bottomup and topdown analyses. 2013-03-26 00:42:09 +00:00
ProvenanceAnalysis.cpp Changed isStoredObjCPointer => IsStoredObjCPointer. No functionality change. 2013-02-12 23:35:08 +00:00
ProvenanceAnalysis.h Fixed some whitespace/80+ violations. Also added a space after a namespace declaration. 2013-01-29 04:58:30 +00:00