Suppress partial retain+release elimination when there's a
possibility that it will span multiple CFG diamonds/triangles which
could have different controlling predicates. rdar://10282956
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142222 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index da74e9c..4e068d5 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -1158,6 +1158,11 @@
/// with the "tail" keyword.
bool IsTailCallRelease;
+ /// Partial - True of we've seen an opportunity for partial RR elimination,
+ /// such as pushing calls into a CFG triangle or into one side of a
+ /// CFG diamond.
+ bool Partial;
+
/// ReleaseMetadata - If the Calls are objc_release calls and they all have
/// a clang.imprecise_release tag, this is the metadata tag.
MDNode *ReleaseMetadata;
@@ -1172,6 +1177,7 @@
RRInfo() :
KnownSafe(false), IsRetainBlock(false), IsTailCallRelease(false),
+ Partial(false),
ReleaseMetadata(0) {}
void clear();
@@ -1182,6 +1188,7 @@
KnownSafe = false;
IsRetainBlock = false;
IsTailCallRelease = false;
+ Partial = false;
ReleaseMetadata = 0;
Calls.clear();
ReverseInsertPts.clear();
@@ -1272,8 +1279,16 @@
if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
Seq = S_None;
+ // If we're not in a sequence (anymore), drop all associated state.
if (Seq == S_None) {
RRI.clear();
+ } else if (RRI.Partial || Other.RRI.Partial) {
+ // If we're doing a merge on a path that's previously seen a partial
+ // merge, conservatively drop the sequence, to avoid doing partial
+ // RR elimination. If the branch predicates for the two merge differ,
+ // mixing them is unsafe.
+ Seq = S_None;
+ RRI.clear();
} else {
// Conservatively merge the ReleaseMetadata information.
if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
@@ -1282,8 +1297,15 @@
RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
RRI.IsTailCallRelease = RRI.IsTailCallRelease && Other.RRI.IsTailCallRelease;
RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
- RRI.ReverseInsertPts.insert(Other.RRI.ReverseInsertPts.begin(),
- Other.RRI.ReverseInsertPts.end());
+
+ // Merge the insert point sets. If there are any differences,
+ // that makes this a partial merge.
+ RRI.Partial = RRI.ReverseInsertPts.size() !=
+ Other.RRI.ReverseInsertPts.size();
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ I = Other.RRI.ReverseInsertPts.begin(),
+ E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
+ RRI.Partial |= RRI.ReverseInsertPts.insert(*I);
}
}