[all-commits] [llvm/llvm-project] ddf43e: revert llvm/include/llvm/Analysis/ObjCARCUtil.h pa...

[Hans via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ddf43e5130d01897906c9b23ae5a0b56f1ac0f78
      https://github.com/llvm/llvm-project/commit/ddf43e5130d01897906c9b23ae5a0b56f1ac0f78
  Author: Hans Wennborg <hans at chromium.org>
  Date:   2021-03-03 (Wed, 03 Mar 2021)

  Changed paths:
    M llvm/include/llvm/Analysis/ObjCARCUtil.h

  Log Message:
  -----------
  revert llvm/include/llvm/Analysis/ObjCARCUtil.h part of 1cc558bd4fa1acd1462226ef4796c712f80ea8e8


  Commit: 0a5dd067181dac2a8882a139ea3bd19bdea5fa44
      https://github.com/llvm/llvm-project/commit/0a5dd067181dac2a8882a139ea3bd19bdea5fa44
  Author: Hans Wennborg <hans at chromium.org>
  Date:   2021-03-03 (Wed, 03 Mar 2021)

  Changed paths:
    M clang/lib/CodeGen/CGObjC.cpp
    M clang/lib/CodeGen/CodeGenFunction.h
    M clang/lib/CodeGen/CodeGenModule.cpp
    M clang/lib/CodeGen/CodeGenModule.h
    R clang/test/CodeGenObjC/arc-rv-attr.m
    M clang/test/CodeGenObjC/arc-unsafeclaim.m
    M llvm/docs/LangRef.rst
    R llvm/include/llvm/Analysis/ObjCARCUtil.h
    M llvm/include/llvm/IR/InstrTypes.h
    M llvm/include/llvm/IR/Intrinsics.td
    M llvm/include/llvm/IR/LLVMContext.h
    M llvm/lib/Analysis/ObjCARCInstKind.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
    M llvm/lib/IR/AutoUpgrade.cpp
    M llvm/lib/IR/Instructions.cpp
    M llvm/lib/IR/LLVMContext.cpp
    M llvm/lib/IR/Verifier.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Transforms/ObjCARC/ARCRuntimeEntryPoints.h
    M llvm/lib/Transforms/ObjCARC/ObjCARC.cpp
    M llvm/lib/Transforms/ObjCARC/ObjCARC.h
    M llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
    M llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
    M llvm/lib/Transforms/ObjCARC/PtrState.cpp
    M llvm/lib/Transforms/ObjCARC/PtrState.h
    M llvm/lib/Transforms/Scalar/SCCP.cpp
    M llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
    M llvm/lib/Transforms/Utils/InlineFunction.cpp
    M llvm/test/Bitcode/operand-bundles-bc-analyzer.ll
    M llvm/test/CodeGen/AArch64/call-rv-marker.ll
    M llvm/test/Transforms/DeadArgElim/deadretval.ll
    R llvm/test/Transforms/Inline/inline-retainRV-call.ll
    M llvm/test/Transforms/ObjCARC/contract-marker-funclet.ll
    R llvm/test/Transforms/ObjCARC/contract-rv-attr.ll
    M llvm/test/Transforms/ObjCARC/contract.ll
    M llvm/test/Transforms/ObjCARC/intrinsic-use.ll
    M llvm/test/Transforms/ObjCARC/rv.ll
    R llvm/test/Transforms/SCCP/clang-arc-rv.ll
    M llvm/test/Transforms/TailCallElim/deopt-bundle.ll
    M llvm/test/Verifier/operand-bundles.ll

  Log Message:
  -----------
  Revert "[ObjC][ARC] Use operand bundle 'clang.arc.attachedcall' instead of explicitly emitting retainRV or claimRV calls in the IR"

This caused miscompiles of Chromium tests for iOS due clobbering of live
registers. See discussion on the code review for details.

> Background:
>
> This fixes a longstanding problem where llvm breaks ARC's autorelease
> optimization (see the link below) by separating calls from the marker
> instructions or retainRV/claimRV calls. The backend changes are in
> https://reviews.llvm.org/D92569.
>
> https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue
>
> What this patch does to fix the problem:
>
> - The front-end adds operand bundle "clang.arc.attachedcall" to calls,
>   which indicates the call is implicitly followed by a marker
>   instruction and an implicit retainRV/claimRV call that consumes the
>   call result. In addition, it emits a call to
>   @llvm.objc.clang.arc.noop.use, which consumes the call result, to
>   prevent the middle-end passes from changing the return type of the
>   called function. This is currently done only when the target is arm64
>   and the optimization level is higher than -O0.
>
> - ARC optimizer temporarily emits retainRV/claimRV calls after the calls
>   with the operand bundle in the IR and removes the inserted calls after
>   processing the function.
>
> - ARC contract pass emits retainRV/claimRV calls after the call with the
>   operand bundle. It doesn't remove the operand bundle on the call since
>   the backend needs it to emit the marker instruction. The retainRV and
>   claimRV calls are emitted late in the pipeline to prevent optimization
>   passes from transforming the IR in a way that makes it harder for the
>   ARC middle-end passes to figure out the def-use relationship between
>   the call and the retainRV/claimRV calls (which is the cause of
>   PR31925).
>
> - The function inliner removes an autoreleaseRV call in the callee if
>   nothing in the callee prevents it from being paired up with the
>   retainRV/claimRV call in the caller. It then inserts a release call if
>   claimRV is attached to the call since autoreleaseRV+claimRV is
>   equivalent to a release. If it cannot find an autoreleaseRV call, it
>   tries to transfer the operand bundle to a function call in the callee.
>   This is important since the ARC optimizer can remove the autoreleaseRV
>   returning the callee result, which makes it impossible to pair it up
>   with the retainRV/claimRV call in the caller. If that fails, it simply
>   emits a retain call in the IR if retainRV is attached to the call and
>   does nothing if claimRV is attached to it.
>
> - SCCP refrains from replacing the return value of a call with a
>   constant value if the call has the operand bundle. This ensures the
>   call always has at least one user (the call to
>   @llvm.objc.clang.arc.noop.use).
>
> - This patch also fixes a bug in replaceUsesOfNonProtoConstant where
>   multiple operand bundles of the same kind were being added to a call.
>
> Future work:
>
> - Use the operand bundle on x86-64.
>
> - Fix the auto upgrader to convert call+retainRV/claimRV pairs into
>   calls with the operand bundles.
>
> rdar://71443534
>
> Differential Revision: https://reviews.llvm.org/D92808

This reverts commit ed4718eccb12bd42214ca4fb17d196d49561c0c7.


Compare: https://github.com/llvm/llvm-project/compare/188373fb4697...0a5dd067181d