forked from OSchip/llvm-project
6 Commits
| Author | SHA1 | Message | Date |
|---|---|---|---|
Akira Hatanaka
|
1900503595 |
[ObjC][ARC] Use operand bundle 'clang.arc.attachedcall' instead of
explicitly emitting retainRV or claimRV calls in the IR This reapplies |
|
|
Hans Wennborg
|
0a5dd06718 |
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
|
|
|
Akira Hatanaka
|
ed4718eccb |
[ObjC][ARC] Use operand bundle 'clang.arc.attachedcall' instead of
explicitly emitting retainRV or claimRV calls in the IR 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 |
|
|
Sanjoy Das
|
a34ce95b60 |
Add a "gc-transition" operand bundle
Summary: This adds a new kind of operand bundle to LLVM denoted by the `"gc-transition"` tag. Inputs to `"gc-transition"` operand bundle are lowered into the "transition args" section of `gc.statepoint` by `RewriteStatepointsForGC`. This removes the last bit of functionality that was unsupported in the deopt bundle based code path in `RewriteStatepointsForGC`. Reviewers: pgavlin, JosephTremoulet, reames Subscribers: sanjoy, mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D16342 llvm-svn: 258338 |
|
|
Sanjoy Das
|
cdafd8490a |
Introduce deoptimization operand bundles
Summary: This change introduces the notion of "deoptimization" operand bundles. LLVM can recognize and optimize these in more precise ways than it can a generic "unknown" operand bundles. The current form of this special recognition / optimization is an enum entry in LLVMContext, a LangRef blurb and a verifier rule. Over time we will teach LLVM to do more aggressive optimization around deoptimization operand bundles, exploiting known facts about kinds of state deoptimization operand bundles are allowed to track. Reviewers: reames, majnemer, chandlerc, dexonsmith Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D14551 llvm-svn: 252806 |
|
|
Sanjoy Das
|
b513a9fa4f |
[Bitcode][Asm] Teach LLVM to read and write operand bundles.
Summary: This also adds the first set of tests for operand bundles. The optimizer has not been audited to ensure that it does the right thing with operand bundles. Depends on D12456. Reviewers: reames, chandlerc, majnemer, dexonsmith, kmod, JosephTremoulet, rnk, bogner Subscribers: maksfb, llvm-commits Differential Revision: http://reviews.llvm.org/D12457 llvm-svn: 248551 |