Reverted due to failures on buildbots, where a new cl flag was placed
in the wrong file, resulting in link errors.
https://lab.llvm.org/buildbot/#/builders/198/builds/8548
This reverts commit 0b398256b3f72204ad1f7c625efe4990204e898a.
This patch adds support for printing the proposed non-instruction debug
info ("RemoveDIs") out to textual IR. This patch does not add any
bitcode support, parsing support, or documentation.
Printing of the new format is controlled by a flag added in this patch,
`--write-experimental-debuginfo`, which defaults to false. The new
format will be printed *iff* this flag is true, so whether we use the IR
format is completely independent of whether we use non-instruction debug
info during LLVM passes (which is controlled by the
`--try-experimental-debuginfo-iterators` flag).
Even with the flag disabled, some existing tests need to be updated, as this
patch causes debug intrinsic declarations to be changed in a round trip,
such that they always appear at the end of a module and have no attributes
(this has no functional change on the module).
The design of this new IR format was proposed previously on
Discourse, and any further discussion about the design can still be
contributed there:
https://discourse.llvm.org/t/rfc-debuginfo-proposed-changes-to-the-textual-ir-representation-for-debug-values/73491
This allows use with non-0 address space stacks. llvm_ptr_ty should
never be used. This could use some more percolation up through mlir,
but this is enough to fix existing tests.
https://reviews.llvm.org/D156666
Stop reordering the pointers passed in ProvenanceAnalysis::related based
on their values. That was causing non-determinism as the call to
relatedCheck(A, B) isn't guaranteed to return the same result as
relatedCheck(B, A).
Revert the following three commits (except the original test case in
related-check.ll):
665e47777df17db406c698d57b4f3c28d67c432e
295861514e0d1e48df2918b630dd692ac27ee0de
d877e3fe71676b0ff10410d80456b35cdd5bf796
These changes shouldn't be necessary once the call to std::swap is
removed.
Differential Revision: https://reviews.llvm.org/D150296
WinEHPrepare requires funclet operand bundles ("tokens") on function calls from EH funclets to prevent them from getting removed as "implausible" calls. This includes calls to intrinsic functions that lower to function calls in the course of IR transformations (e.g. ObjC ARC runtime calls).
We can not detect such cases in WinEHPrepare itself, because at this point they mixed up with valid implausible calls. These must be removed to guarantee that the EH backend can assign unique colors and EH state numbers to all blocks.
This patch allows the IR Verifier to detect missing and dangling funclet tokens. Non-conforming IR becomes illegal and miscompilations are detected early. In order to find funclet pad instructions for funclets that extend over multiple blocks, we have to calculate EH funclet colors. As coloring can be expensive, it runs on-demand and results are cached per function.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D138123
Generalize and share code for operand bundle handling. Drop the anonymous namespace (all other helper functions are local static). Rename the existing funclet test for cleanup-pads.
Reviewed By: compnerd
Differential Revision: https://reviews.llvm.org/D137945
When optimizing retain-release-sequences we insert (and delete) ObjC runtime calls. These calls need a funclet operand bundle that refers to the enclosing funclet pad whenever they are inserted in a WinEH funclet. WinEH funclets can contain multiple basic blocks. In order to find the enclosing funclet pad, we have to calculate the funclet coloring first.
Reviewed By: ahatanak
Differential Revision: https://reviews.llvm.org/D137944
escape.ll needed a simple manual check line update.
contract-storestrong.ll:test12 is kind of contrived now. The comment
says it's for testing bitcasts of pointers, which don't really matter
anymore. Leaves identity ptr to ptr bitcasts (which I thought were
illegal).
These were trying to check if there was not an llvm.objc call before a
closing "}", which presumably was intended to match the end of the
function. Really this was matching the closing } in "bitcast {}* %self
to i8*", which can't be what anyone intended. This broke after
converting the test to opaque pointer deleted this bitcast.
There are in fact @llvm.obj calls remaining in the function, so this
may indicate the transform this was intended to check is actually
broken. In @"\01-[A z]" (great test name), the first retain call seems
to move down to the printf. The second case, @"\01-[Top0 _getX]", has
no change.
Change the checks to what's produced and add FIXMES. Also change the }
checks to match only at the start of the line for the function end.
ProvenanceAnalysis::relatedCheck was giving different answers depending
on the order in which the pointers were passed.
Specifically, it was returning different values when A and B were both
loads and were both referring to identifiable objects, but only one was
used by a store instruction.
This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemonly, inaccessiblememonly and inaccessiblemem_or_argmemonly
attributes are dropped. The readnone, readonly and writeonly attributes
are restricted to parameters only.
The old attributes are auto-upgraded both in bitcode and IR.
The bitcode upgrade is a policy requirement that has to be retained
indefinitely. The IR upgrade is mainly there so it's not necessary
to update all tests using memory attributes in this patch, which
is already large enough. We could drop that part after migrating
tests, or retain it longer term, to make it easier to import IR
from older LLVM versions.
High-level Function/CallBase APIs like doesNotAccessMemory() or
setDoesNotAccessMemory() are mapped transparently to the memory
attribute. Code that directly manipulates attributes (e.g. via
AttributeList) on the other hand needs to switch to working with
the memory attribute instead.
Differential Revision: https://reviews.llvm.org/D135780
`ProvenanceAnalysis::related()` was assuming that the order of parameters for `relatedCheck()` was not affecting
the result but this was not the case when both parameters were `PHINode`s.
Due to this assumption `ProvenanceAnalysis::related()` was ordering the parameters based on pointer value which resulted in
non-deterministic behavior.
To address this change `relatedPHI()` so that it gives the same result independent of the parameter order.
rdar://100325456
Differential Revision: https://reviews.llvm.org/D135376
Currently, the clang.arc.attachedcall bundle takes an optional function
argument. Depending on whether the argument is present, calls with this
bundle have the following semantics:
- on x86, with the argument present, the call is lowered to:
call _target
mov rax, rdi
call _objc_retainAutoreleasedReturnValue
- on AArch64, without the argument, the call is lowered to:
bl _target
mov x29, x29
and the objc runtime call is expected to be emitted separately.
That's because, on x86, the objc runtime checks for both the mov and
the call on x86, and treats the combination as the ARC autorelease elision
marker.
But on AArch64, it only checks for the dedicated NOP marker, as that's
historically been sufficiently unique. Thanks to that, the runtime call
wasn't required to be adjacent to the NOP marker, so it wasn't emitted
as part of the bundle sequence.
This patch unifies both architectures: on AArch64, we now emit all
3 instructions for the bundle. This guarantees that the runtime call
is adjacent to the marker in the sequence, and that's information the
runtime can use to further optimize this.
This helps simplify some of the handling, in particular
BundledRetainClaimRVs, which no longer needs to know whether the bundle
is sufficient or not: it now always should be.
Note that this does not include an AutoUpgrade for the nullary bundles,
as they are only produced in ObjCContract as part of the obj/asm emission
pipeline, and are not expected to be in bitcode.
Differential Revision: https://reviews.llvm.org/D118214
This is what CreateNonTerminatorUnreachable() in InstCombine uses.
Specific choice here doesn't really matter, but we should pick
one that is pointer element type independent.
that don't use the inline asm marker
This patch makes the changes to the ARC middle-end passes that are
needed to handle operand bundle "clang.arc.attachedcall" on targets that
don't use the inline asm marker for the retainRV/autoreleaseRV
handshake (e.g., x86-64).
Note that anyone who wants to use the operand bundle on their target has
to teach their backend to handle the operand bundle. The x86-64 backend
already knows about the operand bundle (see
https://reviews.llvm.org/D94597).
Differential Revision: https://reviews.llvm.org/D111334
integer 0/1 for the operand of bundle "clang.arc.attachedcall"
https://reviews.llvm.org/D102996 changes the operand of bundle
"clang.arc.attachedcall". This patch makes changes to llvm that are
needed to handle the new IR.
This should make it easier to understand what the IR is doing and also
simplify some of the passes as they no longer have to translate the
integer values to the runtime functions.
Differential Revision: https://reviews.llvm.org/D103000
release call
findSafeStoreForStoreStrongContraction checks whether it's safe to move
the release call to the store by inspecting all instructions between the
two, but was ignoring retain instructions. This was causing objects to
be released and deallocated before they were retained.
rdar://81668577
D55348 replaced @objc_msgSend with @llvm.objc.msgSend in tests
together with many other objc intrinsics. However, this is not a
recognized objc intrinsic (https://llvm.org/docs/LangRef.html#objective-c-arc-runtime-intrinsics)
and does not receive special treatment by LLVM. It's likely that
uses of this function were renamed by accident.
This came up in D106013, because the address of @llvm.objs.msgSend
is taken, something which is normally not allowed for intrinsics.
Differential Revision: https://reviews.llvm.org/D106094
that release the retained object
This patch fixes what looks like a longstanding bug in ARC optimizer
where it reverses the order of objc_retain calls and objc_release calls
that retain and release the same object.
The code in ARC optimizer that is responsible for code motion takes the
following steps:
1. Traverse the CFG bottom-up and determine how far up objc_release
calls can be moved. Determine the insertion points for the
objc_release calls, but don't actually move them.
2. Traverse the CFG top-down and determine how far down objc_retain
calls can be moved. Determine the insertion points for the
objc_retain calls, but don't actually move them.
3. Try to move the objc_retain and objc_release calls if they can't be
removed.
The problem is that the insertion points for the objc_retain calls are
determined in step 2 without taking into consideration the insertion
points for objc_release calls determined in step 1, so the order of an
objc_retain call and an objc_release call can be reversed, which is
incorrect, even though each step is correct in isolation.
To fix this bug, this patch teaches the top-down traversal step to take
into consideration the insertion points for objc_release calls
determined in the bottom-up traversal step. Code motion for an
objc_retain call is disabled if there is a possibility that it can be
moved past an objc_release call that releases the retained object.
rdar://79292791
Differential Revision: https://reviews.llvm.org/D104953
the call's return type is void
Instead of trying hard to prevent global optimization passes such as
deadargelim from changing the return type to void, just ignore the
bundle if the return type is void. clang currently emits calls to
@llvm.objc.clang.arc.noop.use, which consumes the function call result,
immediately after the function call to prevent changes to the return
type, but optimization passes can delete the call to
@llvm.objc.clang.arc.noop.use if the function call doesn't return, which
enables deadargelim to change the return type.
rdar://76671438
Differential Revision: https://reviews.llvm.org/D103062
Remove the `nosync` attribute from the memory intrinsic definitions
(i.e. memset, memcpy, memmove).
Like native memory accesses, memory intrinsics can be volatile. This is
indicated by an immarg in the intrinsic call. All else equal, a volatile
memory intrinsic is `sync`, so we cannot annotate the intrinsic functions
themselves as `nosync`. The attributor and function-attr passes know to
take the volatile bit into account.
Since `nosync` is a default attribute, this means we have to stop using
the DefaultAttrIntrinsic tablegen class for memory intrinsics, and
specify all default attributes other than `nosync` explicitly.
Most of the test changes are trivial churn, but one test case
(in nosync.ll) was in fact incorrect before this change.
Differential Revision: https://reviews.llvm.org/D102295
explicitly emitting retainRV or claimRV calls in the IR
This reapplies ed4718eccb12bd42214ca4fb17d196d49561c0c7, which was reverted
because it was causing a miscompile. The bug that was causing the miscompile
has been fixed in 75805dce5ff874676f3559c069fcd6737838f5c0.
Original commit message:
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 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.
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
This reverts commit 4a64d8fe392449b205e59031aad5424968cf7446.
Makes clang crash when buildling trivial iOS programs, see comment
after https://reviews.llvm.org/D92808#2551401
emitting retainRV or claimRV calls in the IR
This reapplies 3fe3946d9a958b7af6130241996d9cfcecf559d4 without the
changes made to lib/IR/AutoUpgrade.cpp, which was violating layering.
Original commit message:
Background:
This patch makes changes to the front-end and middle-end that are
needed to fix 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.rv" 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
the call is annotated with claimRV 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 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 the implicit call is a call to
retainRV and does nothing if it's a call to claimRV.
Future work:
- Use the operand bundle on x86-64.
- Fix the auto upgrader to convert call+retainRV/claimRV pairs into
calls annotated with the operand bundles.
rdar://71443534
Differential Revision: https://reviews.llvm.org/D92808
This reverts commit 3fe3946d9a958b7af6130241996d9cfcecf559d4.
The commit violates layering by including a header from Analysis in
lib/IR/AutoUpgrade.cpp.
emitting retainRV or claimRV calls in the IR
Background:
This patch makes changes to the front-end and middle-end that are
needed to fix 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.rv" 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
the call is annotated with claimRV 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 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 the implicit call is a call to
retainRV and does nothing if it's a call to claimRV.
Future work:
- Use the operand bundle on x86-64.
- Fix the auto upgrader to convert call+retainRV/claimRV pairs into
calls annotated with the operand bundles.
rdar://71443534
Differential Revision: https://reviews.llvm.org/D92808
This reverts commit 53176c168061d6f26dcf3ce4fa59288b7d67255e, which
introduceed a layering violation. LLVM's IR library can't include
headers from Analysis.
or claimRV calls in the IR
Background:
This patch makes changes to the front-end and middle-end that are
needed to fix 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 annotates calls with attribute "clang.arc.rv"="retain"
or "clang.arc.rv"="claim", which indicates the call is implicitly
followed by a marker instruction and a retainRV/claimRV call that
consumes the call result. 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
annotated calls in the IR and removes the inserted calls after
processing the function.
- ARC contract pass emits retainRV/claimRV calls after the annotated
calls. It doesn't remove the attribute on the call since the backend
needs it to emit the marker instruction. The retainRV/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 the autoreleaseRV call in the callee that
returns the result if nothing in the callee prevents it from being
paired up with the calls annotated with "clang.arc.rv"="retain/claim"
in the caller. If the call is annotated with "claim", a release call
is inserted since autoreleaseRV+claimRV is equivalent to a release. If
it cannot find an autoreleaseRV call, it tries to transfer the
attributes to a function call in the callee. This is important since
ARC optimizer can remove the autoreleaseRV call returning the callee
result, which makes it impossible to pair it up with the retainRV or
claimRV call in the caller. If that fails, it simply emits a retain
call in the IR if the call is annotated with "retain" and does nothing
if it's annotated with "claim".
- This patch teaches dead argument elimination pass not to change the
return type of a function if any of the calls to the function are
annotated with attribute "clang.arc.rv". This is necessary since the
pass can incorrectly determine nothing in the IR uses the function
return, which can happen since the front-end no longer explicitly
emits retainRV/claimRV calls in the IR, and change its return type to
'void'.
Future work:
- Use the attribute on x86-64.
- Fix the auto upgrader to convert call+retainRV/claimRV pairs into
calls annotated with the attributes.
rdar://71443534
Differential Revision: https://reviews.llvm.org/D92808
inserted when the original call had a 'returned' argument
The code is testing whether the instruction BBI points to is the call
that is paired up with the retainRV/claimRV call, but it doesn't work
when the call has a 'returned' argument since GetArgRCIdentityRoot looks
through 'returned' arguments.
rdar://72485383
