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[ObjC][ARC] Don't remove autoreleaseRV/retainRV pairs if the call isn't

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a tail call

Previosly ARC optimizer removed the autoreleaseRV/retainRV pair in the
following code, which caused the object returned by @something to be
placed in the autorelease pool because the call to @something isn't a
tail call:

```
  %call = call i8* @something(...)
  %2 = call i8* @objc_retainAutoreleasedReturnValue(i8* %call)
  %3 = call i8* @objc_autoreleaseReturnValue(i8* %2)
  ret i8* %3
```

Fix the bug by checking whether @something is a tail call.

rdar://problem/59275894
This commit is contained in:
ahatanak 2020-03-09 13:20:58 -07:00
parent f3f0aaefef
commit 00ab8cc01c
2 changed files with 23 additions and 2 deletions
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9
lib/Transforms/ObjCARC/ObjCARCOpts.cpp
View File

@ -2296,7 +2296,7 @@ FindPredecessorAutoreleaseWithSafePath(const Value *Arg, BasicBlock *BB,
/// Look for this pattern:
/// \code
/// %call = call i8* @something(...)
/// %call = tail call i8* @something(...)
/// %2 = call i8* @objc_retain(i8* %call)
/// %3 = call i8* @objc_autorelease(i8* %2)
/// ret i8* %3
@ -2344,6 +2344,13 @@ void ObjCARCOpt::OptimizeReturns(Function &F) {
bool HasSafePathToCall = HasSafePathToPredecessorCall(Arg, Retain,
DependingInstructions,
Visited, PA);
// Don't remove retainRV/autoreleaseRV pairs if the call isn't a tail call.
if (GetBasicARCInstKind(Retain) == ARCInstKind::RetainRV &&
GetBasicARCInstKind(Autorelease) == ARCInstKind::AutoreleaseRV &&
!cast<CallInst>(*DependingInstructions.begin())->isTailCall())
continue;
DependingInstructions.clear();
Visited.clear();

16
test/Transforms/ObjCARC/rv.ll
View File

@ -77,7 +77,7 @@ define void @test2() {
; CHECK-NEXT: ret i8* %call
define i8* @test3() {
entry:
%call = call i8* @returner()
%call = tail call i8* @returner()
%0 = call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %call) nounwind
%1 = call i8* @llvm.objc.autoreleaseReturnValue(i8* %0) nounwind
ret i8* %1
@ -387,6 +387,20 @@ bb3:
ret i32* %retval
}
; Don't eliminate the retainRV/autoreleaseRV pair if the call isn't a tail call.
; CHECK-LABEL: define i8* @test28(
; CHECK: call i8* @returner()
; CHECK: call i8* @llvm.objc.retainAutoreleasedReturnValue(
; CHECK: call i8* @llvm.objc.autoreleaseReturnValue(
define i8* @test28() {
entry:
%call = call i8* @returner()
%0 = call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %call) nounwind
%1 = call i8* @llvm.objc.autoreleaseReturnValue(i8* %0) nounwind
ret i8* %1
}
!0 = !{}
; CHECK: attributes [[NUW]] = { nounwind }