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
- // objc_autorelease(x), objc_autoreleaseRV -> objc_release(x) if x is
- // otherwise unused.
+ // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
if (IsAutorelease(Class) && Inst->use_empty()) {
CallInst *Call = cast<CallInst>(Inst);
const Value *Arg = Call->getArgOperand(0);
if (IsAutorelease(Class) && Inst->use_empty()) {
CallInst *Call = cast<CallInst>(Inst);
const Value *Arg = Call->getArgOperand(0);
DependingInstructions.clear();
Visited.clear();
DependingInstructions.clear();
Visited.clear();
- // Convert the autorelease to an autoreleaseRV, since it's
- // returning the value.
- if (AutoreleaseClass == IC_Autorelease) {
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Converting autorelease "
- "=> autoreleaseRV since it's returning a value.\n"
- " In: " << *Autorelease
- << "\n");
- Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
- DEBUG(dbgs() << " Out: " << *Autorelease
- << "\n");
- Autorelease->setTailCall(); // Always tail call autoreleaseRV.
- AutoreleaseClass = IC_AutoreleaseRV;
- }
-
// Check that there is nothing that can affect the reference
// count between the retain and the call.
// Note that Retain need not be in BB.
// Check that there is nothing that can affect the reference
// count between the retain and the call.
// Note that Retain need not be in BB.
-; Same as test11 but the value is returned. Do an RV optimization.
+; Same as test11 but the value is returned. Do not perform an RV optimization
+; since if the frontend emitted code for an __autoreleasing variable, we may
+; want it to be in the autorelease pool.
; CHECK: define i8* @test11b(
; CHECK: tail call i8* @objc_retain(i8* %x) [[NUW]]
; CHECK: define i8* @test11b(
; CHECK: tail call i8* @objc_retain(i8* %x) [[NUW]]
-; CHECK: tail call i8* @objc_autoreleaseReturnValue(i8* %0) [[NUW]]
+; CHECK: call i8* @objc_autorelease(i8* %0) [[NUW]]
; CHECK: }
define i8* @test11b(i8* %x) nounwind {
entry:
; CHECK: }
define i8* @test11b(i8* %x) nounwind {
entry:
%p = call i8* @returner()
call i8* @objc_retainAutoreleasedReturnValue(i8* %p)
%t = call i8* @objc_autoreleaseReturnValue(i8* %p)
%p = call i8* @returner()
call i8* @objc_retainAutoreleasedReturnValue(i8* %p)
%t = call i8* @objc_autoreleaseReturnValue(i8* %p)
- call void @use_pointer(i8* %t)
+ call void @use_pointer(i8* %p)
call void @use_pointer(i8* %p)
call i8* @objc_retainAutoreleasedReturnValue(i8* %p)
%t = call i8* @objc_autoreleaseReturnValue(i8* %p)
call void @use_pointer(i8* %p)
call i8* @objc_retainAutoreleasedReturnValue(i8* %p)
%t = call i8* @objc_autoreleaseReturnValue(i8* %p)
}
; Turn objc_retain into objc_retainAutoreleasedReturnValue if its operand
}
; Turn objc_retain into objc_retainAutoreleasedReturnValue if its operand
-; Apply the RV optimization.
+; Do not apply the RV optimization.
; CHECK: define i8* @test10(i8* %p)
; CHECK: tail call i8* @objc_retain(i8* %p) [[NUW]]
; CHECK: define i8* @test10(i8* %p)
; CHECK: tail call i8* @objc_retain(i8* %p) [[NUW]]
-; CHECK: tail call i8* @objc_autoreleaseReturnValue(i8* %p) [[NUW]]
+; CHECK: call i8* @objc_autorelease(i8* %p) [[NUW]]
; CHECK-NEXT: ret i8* %p
define i8* @test10(i8* %p) {
%1 = call i8* @objc_retain(i8* %p)
; CHECK-NEXT: ret i8* %p
define i8* @test10(i8* %p) {
%1 = call i8* @objc_retain(i8* %p)
-; If we convert a called @objc_autorelease to an @objc_autoreleaseReturnValue,
-; ensure that the tail call is added.
-define i8* @test6(i8* %x) {
-entry:
- ; CHECK: %tmp0 = tail call i8* @objc_retain(i8* %x)
- %tmp0 = tail call i8* @objc_retain(i8* %x)
- ; CHECK: %tmp1 = tail call i8* @objc_autoreleaseReturnValue(i8* %x)
- %tmp1 = call i8* @objc_autorelease(i8* %x)
- ret i8* %x
-}