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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

llvm-svn: 142222
This commit is contained in:
Dan Gohman 2011-10-17 18:48:25 +00:00
parent 63a4ea1859
commit 1736c14b85
2 changed files with 55 additions and 2 deletions
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26
llvm/lib/Transforms/Scalar/ObjCARC.cpp
View File

@ -1158,6 +1158,11 @@ namespace {
/// 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 @@ namespace {
RRInfo() :
KnownSafe(false), IsRetainBlock(false), IsTailCallRelease(false),
Partial(false),
ReleaseMetadata(0) {}
void clear();
@ -1182,6 +1188,7 @@ void RRInfo::clear() {
KnownSafe = false;
IsRetainBlock = false;
IsTailCallRelease = false;
Partial = false;
ReleaseMetadata = 0;
Calls.clear();
ReverseInsertPts.clear();
@ -1272,8 +1279,16 @@ PtrState::Merge(const PtrState &Other, bool TopDown) {
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 @@ PtrState::Merge(const PtrState &Other, bool TopDown) {
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);
}
}

31
llvm/test/Transforms/ObjCARC/basic.ll
View File

@ -86,6 +86,37 @@ alt_return:
ret void
}
; Don't do partial elimination into two different CFG diamonds.
; CHECK: define void @test1b(
; CHECK: entry:
; CHECK: tail call i8* @objc_retain(i8* %x) nounwind
; CHECK-NOT: @objc_
; CHECK: if.end5:
; CHECK: tail call void @objc_release(i8* %x) nounwind, !clang.imprecise_release !0
; CHECK-NOT: @objc_
; CHECK: }
define void @test1b(i8* %x, i1 %p, i1 %q) {
entry:
tail call i8* @objc_retain(i8* %x) nounwind
br i1 %p, label %if.then, label %if.end
if.then: ; preds = %entry
tail call void @callee()
br label %if.end
if.end: ; preds = %if.then, %entry
br i1 %q, label %if.then3, label %if.end5
if.then3: ; preds = %if.end
tail call void @use_pointer(i8* %x)
br label %if.end5
if.end5: ; preds = %if.then3, %if.end
tail call void @objc_release(i8* %x) nounwind, !clang.imprecise_release !0
ret void
}
; Like test0 but the pointer is passed to an intervening call,
; so the optimization is not safe.