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

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a tail call

This reapplies the patch in https://reviews.llvm.org/rG1f5b471b8bf4,
which was reverted because it was causing crashes.

https://bugs.chromium.org/p/chromium/issues/detail?id=1061289#c2

Check that HasSafePathToCall is true before checking the call is a tail
call.

Original commit message:

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:
Akira Hatanaka 2020-03-13 12:15:17 -07:00
parent 79c06fdf27
commit a30499dbf2
2 changed files with 49 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
lib/Transforms/ObjCARC/ObjCARCOpts.cpp
View File

@ -2344,6 +2344,14 @@ 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 (HasSafePathToCall &&
GetBasicARCInstKind(Retain) == ARCInstKind::RetainRV &&
GetBasicARCInstKind(Autorelease) == ARCInstKind::AutoreleaseRV &&
!cast<CallInst>(*DependingInstructions.begin())->isTailCall())
continue;
DependingInstructions.clear();
Visited.clear();

42
test/Transforms/ObjCARC/rv.ll
View File

@ -21,6 +21,8 @@ declare void @callee()
declare void @callee_fnptr(void ()*)
declare void @invokee()
declare i8* @returner()
declare i8* @returner1(i8*)
declare i32 @__gxx_personality_v0(...)
; Test that retain+release elimination is suppressed when the
; retain is an objc_retainAutoreleasedReturnValue, since it's
@ -77,7 +79,7 @@ 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 +389,44 @@ 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
}
; CHECK-LABEL: define i8* @test29(
; CHECK: call i8* @llvm.objc.retainAutoreleasedReturnValue(
; CHECK: call i8* @llvm.objc.autoreleaseReturnValue(
define i8* @test29(i8* %k) local_unnamed_addr personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
entry:
%0 = tail call i8* @llvm.objc.retain(i8* %k)
%call = invoke i8* @returner1(i8* %k)
to label %invoke.cont unwind label %lpad
invoke.cont:
%1 = bitcast i8* %call to i8*
%2 = notail call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %1)
tail call void @llvm.objc.release(i8* %k), !clang.imprecise_release !0
%3 = tail call i8* @llvm.objc.autoreleaseReturnValue(i8* %1)
ret i8* %call
lpad:
%4 = landingpad { i8*, i32 }
cleanup
tail call void @llvm.objc.release(i8* %k) #1, !clang.imprecise_release !0
resume { i8*, i32 } %4
}
!0 = !{}
; CHECK: attributes [[NUW]] = { nounwind }