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Fixed a bug where we were tail calling objc_autorelease causing an object to not be placed into an autorelease pool. 

The reason that this occurs is that tail calling objc_autorelease eventually
tail calls -[NSObject autorelease] which supports fast autorelease. This can
cause us to violate the semantic gaurantees of __autoreleasing variables that
assignment to an __autoreleasing variables always yields an object that is
placed into the innermost autorelease pool.

The fix included in this patch works by:

1. In the peephole optimization function OptimizeIndividualFunctions, always
remove tail call from objc_autorelease.
2. Whenever we convert to/from an objc_autorelease, set/unset the tail call
keyword as appropriate.

*NOTE* I also handled the case where objc_autorelease is converted in
OptimizeReturns to an autoreleaseRV which still violates the ARC semantics. I
will be removing that in a later patch and I wanted to make sure that the tree
is in a consistent state vis-a-vis ARC always.

Additionally some test cases are provided and all tests that have tail call marked
objc_autorelease keywords have been modified so that tail call has been removed.

*NOTE* One test fails due to a separate bug that I am going to commit soon. Thus
I marked the check line TMP: instead of CHECK: so make check does not fail.

llvm-svn: 172287
This commit is contained in:
Michael Gottesman 2013-01-12 01:25:15 +00:00
parent e274088db0
commit c9656faf1e
6 changed files with 122 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
llvm/lib/Transforms/Scalar/ObjCARC.cpp
View File

@ -426,10 +426,20 @@ static bool IsAlwaysTail(InstructionClass Class) {
// IC_RetainBlock may be given a stack argument.
return Class == IC_Retain ||
Class == IC_RetainRV ||
Class == IC_Autorelease ||
Class == IC_AutoreleaseRV;
}
/// \brief Test if the given class represents instructions which are never safe
/// to mark with the "tail" keyword.
static bool IsNeverTail(InstructionClass Class) {
/// It is never safe to tail call objc_autorelease since by tail calling
/// objc_autorelease, we also tail call -[NSObject autorelease] which supports
/// fast autoreleasing causing our object to be potentially reclaimed from the
/// autorelease pool which violates the semantics of __autoreleasing types in
/// ARC.
return Class == IC_Autorelease;
}
/// IsNoThrow - Test if the given class represents instructions which are always
/// safe to mark with the nounwind attribute..
static bool IsNoThrow(InstructionClass Class) {
@ -2306,8 +2316,10 @@ ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) {
" Old: "
<< *AutoreleaseRV << "\n");
cast<CallInst>(AutoreleaseRV)->
CallInst *AutoreleaseRVCI = cast<CallInst>(AutoreleaseRV);
AutoreleaseRVCI->
setCalledFunction(getAutoreleaseCallee(F.getParent()));
AutoreleaseRVCI->setTailCall(false); // Never tail call objc_autorelease.
DEBUG(dbgs() << " New: "
<< *AutoreleaseRV << "\n");
@ -2449,6 +2461,16 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
cast<CallInst>(Inst)->setTailCall();
}
// Ensure that functions that can never have a "tail" keyword due to the
// semantics of ARC truly do not do so.
if (IsNeverTail(Class)) {
Changed = true;
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Removing tail keyword"
" from function: " << *Inst <<
"\n");
cast<CallInst>(Inst)->setTailCall(false);
}
// Set nounwind as needed.
if (IsNoThrow(Class)) {
Changed = true;
@ -3756,6 +3778,7 @@ void ObjCARCOpt::OptimizeReturns(Function &F) {
Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
DEBUG(dbgs() << " Out: " << *Autorelease
<< "\n");
Autorelease->setTailCall(); // Always tail call autoreleaseRV.
AutoreleaseClass = IC_AutoreleaseRV;
}

6
llvm/test/Transforms/ObjCARC/basic.ll
View File

@ -405,7 +405,7 @@ entry:
; CHECK: define void @test11(
; CHECK: tail call i8* @objc_retain(i8* %x) nounwind
; CHECK: tail call i8* @objc_autorelease(i8* %0) nounwind
; CHECK: call i8* @objc_autorelease(i8* %0) nounwind
; CHECK: }
define void @test11(i8* %x) nounwind {
entry:
@ -465,7 +465,7 @@ entry:
; CHECK: tail call i8* @objc_retain(i8* %x) nounwind
; CHECK: tail call i8* @objc_retain(i8* %x) nounwind
; CHECK: @use_pointer(i8* %x)
; CHECK: tail call i8* @objc_autorelease(i8* %x) nounwind
; CHECK: call i8* @objc_autorelease(i8* %x) nounwind
; CHECK: }
define void @test13(i8* %x, i64 %n) {
entry:
@ -1452,7 +1452,7 @@ define void @test45(i8** %pp, i8** %qq) {
; CHECK: define void @test46(
; CHECK: tail call i8* @objc_retain(i8* %p) nounwind
; CHECK: true:
; CHECK: tail call i8* @objc_autorelease(i8* %p) nounwind
; CHECK: call i8* @objc_autorelease(i8* %p) nounwind
define void @test46(i8* %p, i1 %a) {
entry:
call i8* @objc_retain(i8* %p)

10
llvm/test/Transforms/ObjCARC/contract.ll
View File

@ -39,7 +39,7 @@ entry:
define void @test2(i8* %x) nounwind {
entry:
%0 = tail call i8* @objc_retain(i8* %x) nounwind
tail call i8* @objc_autorelease(i8* %0) nounwind
call i8* @objc_autorelease(i8* %0) nounwind
call void @use_pointer(i8* %x)
ret void
}
@ -66,7 +66,7 @@ define void @test3(i8* %x, i64 %n) {
entry:
tail call i8* @objc_retain(i8* %x) nounwind
call void @use_pointer(i8* %x)
tail call i8* @objc_autorelease(i8* %x) nounwind
call i8* @objc_autorelease(i8* %x) nounwind
ret void
}
@ -84,7 +84,7 @@ define void @test4(i8* %x, i64 %n) {
entry:
tail call i8* @objc_retain(i8* %x) nounwind
call void @use_pointer(i8* %x)
tail call i8* @objc_autorelease(i8* %x) nounwind
call i8* @objc_autorelease(i8* %x) nounwind
tail call void @objc_release(i8* %x) nounwind
ret void
}
@ -94,7 +94,7 @@ entry:
; CHECK: define void @test5(
; CHECK: tail call i8* @objc_retain(i8* %p) nounwind
; CHECK: true:
; CHECK: tail call i8* @objc_autorelease(i8* %0) nounwind
; CHECK: call i8* @objc_autorelease(i8* %0) nounwind
; CHECK: }
define void @test5(i8* %p, i1 %a) {
entry:
@ -102,7 +102,7 @@ entry:
br i1 %a, label %true, label %false
true:
tail call i8* @objc_autorelease(i8* %p) nounwind
call i8* @objc_autorelease(i8* %p) nounwind
call void @use_pointer(i8* %p)
ret void

2
llvm/test/Transforms/ObjCARC/move-and-form-retain-autorelease.ll
View File

@ -212,7 +212,7 @@ bb99: ; preds = %bb57
br label %bb104
bb104: ; preds = %bb99, %bb57
%tmp105 = tail call i8* @objc_autorelease(i8* %tmp72) nounwind
%tmp105 = call i8* @objc_autorelease(i8* %tmp72) nounwind
%tmp106 = bitcast i8* %tmp105 to %14*
tail call void @objc_release(i8* %tmp85) nounwind
%tmp107 = bitcast %18* %tmp47 to i8*

8
llvm/test/Transforms/ObjCARC/rv.ll
View File

@ -150,7 +150,7 @@ define void @test8() {
; Don't apply the RV optimization to autorelease if there's no retain.
; CHECK: define i8* @test9(i8* %p)
; CHECK: tail call i8* @objc_autorelease(i8* %p)
; CHECK: call i8* @objc_autorelease(i8* %p)
define i8* @test9(i8* %p) {
call i8* @objc_autorelease(i8* %p)
ret i8* %p
@ -174,7 +174,7 @@ define i8* @test10(i8* %p) {
; CHECK: define i8* @test11(i8* %p)
; CHECK: tail call i8* @objc_retain(i8* %p)
; CHECK-NEXT: call void @use_pointer(i8* %p)
; CHECK: tail call i8* @objc_autorelease(i8* %p)
; CHECK: call i8* @objc_autorelease(i8* %p)
; CHECK-NEXT: ret i8* %p
define i8* @test11(i8* %p) {
%1 = call i8* @objc_retain(i8* %p)
@ -201,7 +201,7 @@ define i8* @test12(i8* %p) {
; CHECK: define i8* @test13(
; CHECK: tail call i8* @objc_retainAutoreleasedReturnValue(i8* %p)
; CHECK: tail call i8* @objc_autorelease(i8* %p)
; CHECK: call i8* @objc_autorelease(i8* %p)
; CHECK: ret i8* %p
define i8* @test13() {
%p = call i8* @returner()
@ -323,7 +323,7 @@ define i8* @test22(i8* %p) {
; Convert autoreleaseRV to autorelease.
; CHECK: define void @test23(
; CHECK: tail call i8* @objc_autorelease(i8* %p) nounwind
; CHECK: call i8* @objc_autorelease(i8* %p) nounwind
define void @test23(i8* %p) {
store i8 0, i8* %p
call i8* @objc_autoreleaseReturnValue(i8* %p)

84
llvm/test/Transforms/ObjCARC/tail-call-invariant-enforcement.ll Normal file
View File

@ -0,0 +1,84 @@
; RUN: opt -objc-arc -S < %s | FileCheck %s
declare i8* @objc_release(i8* %x)
declare i8* @objc_retain(i8* %x)
declare i8* @objc_autorelease(i8* %x)
declare i8* @objc_autoreleaseReturnValue(i8* %x)
declare i8* @objc_retainAutoreleasedReturnValue(i8* %x)
; Never tail call objc_autorelease.
define i8* @test0(i8* %x) {
entry:
; CHECK: %tmp0 = call i8* @objc_autorelease(i8* %x)
%tmp0 = call i8* @objc_autorelease(i8* %x)
; CHECK: %tmp1 = call i8* @objc_autorelease(i8* %x)
%tmp1 = tail call i8* @objc_autorelease(i8* %x)
ret i8* %x
}
; Always tail call autoreleaseReturnValue.
define i8* @test1(i8* %x) {
entry:
; CHECK: %tmp0 = tail call i8* @objc_autoreleaseReturnValue(i8* %x)
%tmp0 = call i8* @objc_autoreleaseReturnValue(i8* %x)
; CHECK: %tmp1 = tail call i8* @objc_autoreleaseReturnValue(i8* %x)
%tmp1 = tail call i8* @objc_autoreleaseReturnValue(i8* %x)
ret i8* %x
}
; Always tail call objc_retain.
define i8* @test2(i8* %x) {
entry:
; CHECK: %tmp0 = tail call i8* @objc_retain(i8* %x)
%tmp0 = call i8* @objc_retain(i8* %x)
; CHECK: %tmp1 = tail call i8* @objc_retain(i8* %x)
%tmp1 = tail call i8* @objc_retain(i8* %x)
ret i8* %x
}
define i8* @tmp(i8* %x) {
ret i8* %x
}
; Always tail call objc_retainAutoreleasedReturnValue.
define i8* @test3(i8* %x) {
entry:
%y = call i8* @tmp(i8* %x)
; CHECK: %tmp0 = tail call i8* @objc_retainAutoreleasedReturnValue(i8* %y)
%tmp0 = call i8* @objc_retainAutoreleasedReturnValue(i8* %y)
%z = call i8* @tmp(i8* %x)
; CHECK: %tmp1 = tail call i8* @objc_retainAutoreleasedReturnValue(i8* %z)
%tmp1 = tail call i8* @objc_retainAutoreleasedReturnValue(i8* %z)
ret i8* %x
}
; By itself, we should never change whether or not objc_release is tail called.
define i8* @test4(i8* %x) {
entry:
; CHECK: %tmp0 = call i8* @objc_release(i8* %x)
%tmp0 = call i8* @objc_release(i8* %x)
; CHECK: %tmp1 = tail call i8* @objc_release(i8* %x)
%tmp1 = tail call i8* @objc_release(i8* %x)
ret i8* %x
}
; If we convert a tail called @objc_autoreleaseReturnValue to an
; @objc_autorelease, ensure that the tail call is removed.
define i8* @test5(i8* %x) {
entry:
; TMP: %tmp0 = call i8* @objc_autorelease(i8* %x)
%tmp0 = tail call i8* @objc_autoreleaseReturnValue(i8* %x)
ret i8* %tmp0
}
; 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
}