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It's not possible to insert code immediately after an invoke in the

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same basic block, and it's not safe to insert code in the successor
blocks if the edges are critical edges. Splitting those edges is
possible, but undesirable, especially on the unwind side. Instead,
make the bottom-up code motion to consider invokes to be part of
their successor blocks, rather than part of their parent blocks, so
that it doesn't push code past them and onto the edges. This fixes
PR12307.

llvm-svn: 153343
This commit is contained in:
Dan Gohman 2012-03-23 17:47:54 +00:00
parent 7da86bf59f
commit 0c02608af1
2 changed files with 108 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
lib/Transforms/Scalar/ObjCARC.cpp
View File

@ -1679,6 +1679,7 @@ namespace {
DenseMap<const BasicBlock *, BBState> &BBStates,
BBState &MyStates) const;
bool VisitInstructionBottomUp(Instruction *Inst,
BasicBlock *BB,
MapVector<Value *, RRInfo> &Retains,
BBState &MyStates);
bool VisitBottomUp(BasicBlock *BB,
@ -2523,6 +2524,7 @@ ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
bool
ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
BasicBlock *BB,
MapVector<Value *, RRInfo> &Retains,
BBState &MyStates) {
bool NestingDetected = false;
@ -2642,14 +2644,24 @@ ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
case S_MovableRelease:
if (CanUse(Inst, Ptr, PA, Class)) {
assert(S.RRI.ReverseInsertPts.empty());
S.RRI.ReverseInsertPts.insert(Inst);
// If this is an invoke instruction, we're scanning it as part of
// one of its successor blocks, since we can't insert code after it
// in its own block, and we don't want to split critical edges.
if (isa<InvokeInst>(Inst))
S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
else
S.RRI.ReverseInsertPts.insert(next(BasicBlock::iterator(Inst)));
S.SetSeq(S_Use);
} else if (Seq == S_Release &&
(Class == IC_User || Class == IC_CallOrUser)) {
// Non-movable releases depend on any possible objc pointer use.
S.SetSeq(S_Stop);
assert(S.RRI.ReverseInsertPts.empty());
S.RRI.ReverseInsertPts.insert(Inst);
// As above; handle invoke specially.
if (isa<InvokeInst>(Inst))
S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
else
S.RRI.ReverseInsertPts.insert(next(BasicBlock::iterator(Inst)));
}
break;
case S_Stop:
@ -2713,7 +2725,23 @@ ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
// Visit all the instructions, bottom-up.
for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
Instruction *Inst = llvm::prior(I);
NestingDetected |= VisitInstructionBottomUp(Inst, Retains, MyStates);
// Invoke instructions are visited as part of their successors (below).
if (isa<InvokeInst>(Inst))
continue;
NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
}
// If there's a predecessor with an invoke, visit the invoke as
// if it were part of this block, since we can't insert code after
// an invoke in its own block, and we don't want to split critical
// edges.
for (pred_iterator PI(BB), PE(BB, false); PI != PE; ++PI) {
BasicBlock *Pred = *PI;
TerminatorInst *PredTI = cast<TerminatorInst>(&Pred->back());
if (isa<InvokeInst>(PredTI))
NestingDetected |= VisitInstructionBottomUp(PredTI, BB, Retains, MyStates);
}
return NestingDetected;
@ -3058,35 +3086,17 @@ void ObjCARCOpt::MoveCalls(Value *Arg,
for (SmallPtrSet<Instruction *, 2>::const_iterator
PI = RetainsToMove.ReverseInsertPts.begin(),
PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
Instruction *LastUse = *PI;
Instruction *InsertPts[] = { 0, 0, 0 };
if (InvokeInst *II = dyn_cast<InvokeInst>(LastUse)) {
// We can't insert code immediately after an invoke instruction, so
// insert code at the beginning of both successor blocks instead.
// The invoke's return value isn't available in the unwind block,
// but our releases will never depend on it, because they must be
// paired with retains from before the invoke.
InsertPts[0] = II->getNormalDest()->getFirstInsertionPt();
if (!II->getMetadata(NoObjCARCExceptionsMDKind))
InsertPts[1] = II->getUnwindDest()->getFirstInsertionPt();
} else {
// Insert code immediately after the last use.
InsertPts[0] = llvm::next(BasicBlock::iterator(LastUse));
}
for (Instruction **I = InsertPts; *I; ++I) {
Instruction *InsertPt = *I;
Value *MyArg = ArgTy == ParamTy ? Arg :
new BitCastInst(Arg, ParamTy, "", InsertPt);
CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
"", InsertPt);
// Attach a clang.imprecise_release metadata tag, if appropriate.
if (MDNode *M = ReleasesToMove.ReleaseMetadata)
Call->setMetadata(ImpreciseReleaseMDKind, M);
Call->setDoesNotThrow();
if (ReleasesToMove.IsTailCallRelease)
Call->setTailCall();
}
Instruction *InsertPt = *PI;
Value *MyArg = ArgTy == ParamTy ? Arg :
new BitCastInst(Arg, ParamTy, "", InsertPt);
CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
"", InsertPt);
// Attach a clang.imprecise_release metadata tag, if appropriate.
if (MDNode *M = ReleasesToMove.ReleaseMetadata)
Call->setMetadata(ImpreciseReleaseMDKind, M);
Call->setDoesNotThrow();
if (ReleasesToMove.IsTailCallRelease)
Call->setTailCall();
}
// Delete the original retain and release calls.

66
test/Transforms/ObjCARC/invoke.ll
View File

@ -103,6 +103,72 @@ finally.rethrow: ; preds = %invoke.cont, %entry
unreachable
}
; Don't try to place code on invoke critical edges.
; CHECK: define void @test3(
; CHECK: if.end:
; CHECK-NEXT: call void @objc_release(i8* %p) nounwind
; CHECK-NEXT: ret void
define void @test3(i8* %p, i1 %b) {
entry:
%0 = call i8* @objc_retain(i8* %p)
call void @callee()
br i1 %b, label %if.else, label %if.then
if.then:
invoke void @use_pointer(i8* %p)
to label %if.end unwind label %lpad, !clang.arc.no_objc_arc_exceptions !0
if.else:
invoke void @use_pointer(i8* %p)
to label %if.end unwind label %lpad, !clang.arc.no_objc_arc_exceptions !0
lpad:
%r = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__objc_personality_v0 to i8*)
cleanup
ret void
if.end:
call void @objc_release(i8* %p)
ret void
}
; Like test3, but with ARC-relevant exception handling.
; CHECK: define void @test4(
; CHECK: lpad:
; CHECK-NEXT: %r = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__objc_personality_v0 to i8*)
; CHECK-NEXT: cleanup
; CHECK-NEXT: call void @objc_release(i8* %p) nounwind
; CHECK-NEXT: ret void
; CHECK: if.end:
; CHECK-NEXT: call void @objc_release(i8* %p) nounwind
; CHECK-NEXT: ret void
define void @test4(i8* %p, i1 %b) {
entry:
%0 = call i8* @objc_retain(i8* %p)
call void @callee()
br i1 %b, label %if.else, label %if.then
if.then:
invoke void @use_pointer(i8* %p)
to label %if.end unwind label %lpad
if.else:
invoke void @use_pointer(i8* %p)
to label %if.end unwind label %lpad
lpad:
%r = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__objc_personality_v0 to i8*)
cleanup
call void @objc_release(i8* %p)
ret void
if.end:
call void @objc_release(i8* %p)
ret void
}
declare i32 @__gxx_personality_v0(...)
declare i32 @__objc_personality_v0(...)