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
Turning retains into retainRV calls disrupts the data flow analysis in
ObjCARCOpts. Thus we move it as late as we can by moving it into
ObjCARCContract.
We leave in the conversion from retainRV -> retain in ObjCARCOpt since
it enables the dataflow analysis.
rdar://10813093
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180698 91177308-0d34-0410-b5e6-96231b3b80d8
Mainly adding paranoid checks for the closing brace of a function to
help with FileCheck error readability. Also some other minor changes.
No actual CHECK changes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180668 91177308-0d34-0410-b5e6-96231b3b80d8
Specifically:
1. Added checks that unwind is being properly added to various instructions.
2. Fixed the declaration/calling of objc_release to have a return type of void.
3. Moved all checks to precede the functions and added checks to ensure that the
checks would only match inside the specific function that we are attempting to
check.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179973 91177308-0d34-0410-b5e6-96231b3b80d8
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
This is the counterpart to commit r160637, except it performs the action
in the bottomup portion of the data flow analysis.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178922 91177308-0d34-0410-b5e6-96231b3b80d8
The normal dataflow sequence in the ARC optimizer consists of the following
states:
Retain -> CanRelease -> Use -> Release
The optimizer before this patch stored the uses that determine the lifetime of
the retainable object pointer when it bottom up hits a retain or when top down
it hits a release. This is correct for an imprecise lifetime scenario since what
we are trying to do is remove retains/releases while making sure that no
``CanRelease'' (which is usually a call) deallocates the given pointer before we
get to the ``Use'' (since that would cause a segfault).
If we are considering the precise lifetime scenario though, this is not
correct. In such a situation, we *DO* care about the previous sequence, but
additionally, we wish to track the uses resulting from the following incomplete
sequences:
Retain -> CanRelease -> Release (TopDown)
Retain <- Use <- Release (BottomUp)
*NOTE* This patch looks large but the most of it consists of updating
test cases. Additionally this fix exposed an additional bug. I removed
the test case that expressed said bug and will recommit it with the fix
in a little bit.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178921 91177308-0d34-0410-b5e6-96231b3b80d8
The semantics of ARC implies that a pointer passed into an objc_autorelease
must live until some point (potentially down the stack) where an
autorelease pool is popped. On the other hand, an
objc_autoreleaseReturnValue just signifies that the object must live
until the end of the given function at least.
Thus objc_autorelease is stronger than objc_autoreleaseReturnValue in
terms of the semantics of ARC* implying that performing the given
strength reduction without any knowledge of how this relates to
the autorelease pool pop that is further up the stack violates the
semantics of ARC.
*Even though objc_autoreleaseReturnValue if you know that no RV
optimization will occur is more computationally expensive.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178612 91177308-0d34-0410-b5e6-96231b3b80d8
Specifically, objc-arc-expand will make sure that the
objc_retainAutoreleasedReturnValue, objc_autoreleaseReturnValue, and ret
will all have %call as an argument.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178382 91177308-0d34-0410-b5e6-96231b3b80d8
clang.arc.used is an interesting call for ARC since ObjCARCContract
needs to run to remove said intrinsic to avoid a linker error (since the
call does not exist).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178369 91177308-0d34-0410-b5e6-96231b3b80d8
Since we handle optimizable objc_retainBlocks through strength reduction
in OptimizableIndividualCalls, we know that all code after that point
will only see non-optimizable objc_retainBlock calls. IsForwarding is
only called by functions after that point, so it is ok to just classify
objc_retainBlock as non-forwarding.
<rdar://problem/13249661>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178285 91177308-0d34-0410-b5e6-96231b3b80d8
If an objc_retainBlock has the copy_on_escape metadata attached to it
AND if the block pointer argument only escapes down the stack, we are
allowed to strength reduce the objc_retainBlock to to an objc_retain and
thus optimize it.
Current there is logic in the ARC data flow analysis to handle
this case which is complicated and involved making distinctions in
between objc_retainBlock and objc_retain in certain places and
considering them the same in others.
This patch simplifies said code by:
1. Performing the strength reduction in the initial ARC peephole
analysis (ObjCARCOpts::OptimizeIndividualCalls).
2. Changes the ARC dataflow analysis (which runs after the peephole
analysis) to consider all objc_retainBlock calls to not be optimizable
(since if the call was optimizable, we would have strength reduced it
already).
This patch leaves in the infrastructure in the ARC dataflow analysis to
handle this case, which due to 2 will just be dead code. I am doing this
on purpose to separate the removal of the old code from the testing of
the new code.
<rdar://problem/13249661>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178284 91177308-0d34-0410-b5e6-96231b3b80d8
The test was removed since I had not turned off the test during release
builds. This fails since ARC annotations support is conditionally
compiled out during release builds. I added the proper requires header
to assuage this issue.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178101 91177308-0d34-0410-b5e6-96231b3b80d8
This will allow for verification and analysis of the merge function of
the data flow analyses in the ARC optimizer.
The actual implementation of this feature is by introducing calls to
the functions llvm.arc.annotation.{bottomup,topdown}.{bbstart,bbend}
which are only declared. Each such call takes in a pointer to a global
with the same name as the pointer whose provenance is being tracked and
a pointer whose name is one of our Sequence states and points to a
string that contains the same name.
To ensure that the optimizer does not consider these annotations in any
way, I made it so that the annotations are considered to be of IC_None
type.
A test case is included for this commit and the previous
ObjCARCAnnotation commit.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177952 91177308-0d34-0410-b5e6-96231b3b80d8
*NOTE* I verified that the original bug behind
dont-infinite-loop-during-block-escape-analysis.ll occurs when using opt on
retain-block-escape-analysis.ll.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177240 91177308-0d34-0410-b5e6-96231b3b80d8
This test makes sure that the ObjCARC escape analysis looks at the uses of
instructions which copy the block pointer value by checking all four cases where
that can occur.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177232 91177308-0d34-0410-b5e6-96231b3b80d8
Listing all of the attributes for the callee of a call/invoke instruction is way
too much and makes the IR unreadable. Use references to attributes instead.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175877 91177308-0d34-0410-b5e6-96231b3b80d8
allows for gvn to perform certain optimizations. Thus the runline should
only contain -objc-arc-aa, not the full -objc-arc.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173126 91177308-0d34-0410-b5e6-96231b3b80d8
The reason that this occurs is that tail calling objc_autorelease eventually
tail calls -[NSObject autorelease] which supports fast autorelease. This can
cause us to violate the semantic gaurantees of __autoreleasing variables that
assignment to an __autoreleasing variables always yields an object that is
placed into the innermost autorelease pool.
The fix included in this patch works by:
1. In the peephole optimization function OptimizeIndividualFunctions, always
remove tail call from objc_autorelease.
2. Whenever we convert to/from an objc_autorelease, set/unset the tail call
keyword as appropriate.
*NOTE* I also handled the case where objc_autorelease is converted in
OptimizeReturns to an autoreleaseRV which still violates the ARC semantics. I
will be removing that in a later patch and I wanted to make sure that the tree
is in a consistent state vis-a-vis ARC always.
Additionally some test cases are provided and all tests that have tail call marked
objc_autorelease keywords have been modified so that tail call has been removed.
*NOTE* One test fails due to a separate bug that I am going to commit soon. Thus
I marked the check line TMP: instead of CHECK: so make check does not fail.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172287 91177308-0d34-0410-b5e6-96231b3b80d8
pointers-to-strong-pointers may be in play. These can lead to retains and
releases happening in unstructured ways, foiling the optimizer. This fixes
rdar://12150909.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163180 91177308-0d34-0410-b5e6-96231b3b80d8
I really need to find a way to automate this, but I can't come up with a regex
that has no false positives while handling tricky cases like custom check
prefixes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162097 91177308-0d34-0410-b5e6-96231b3b80d8
library return value optimization for phi uses. Even when the
phi itself is not dominated, the specific use may be dominated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154647 91177308-0d34-0410-b5e6-96231b3b80d8
