forked from OSchip/llvm-project
[BasicAA] Fix handling of invariant group launders
Summary: A recent patch ([[ https://reviews.llvm.org/rL331587 | rL331587 ]]) to Capture Tracking taught it that the `launder_invariant_group` intrinsic captures its argument only by returning it. Unfortunately, BasicAA still considered every call instruction as a possible escape source and hence concluded that the result of a `launder_invariant_group` call cannot alias any local non-escaping value. This led to [[ https://bugs.llvm.org/show_bug.cgi?id=37458 | bug 37458 ]]. This patch updates the relevant check for escape sources in BasicAA. Reviewers: Prazek, kuhar, rsmith, hfinkel, sanjoy, xbolva00 Reviewed By: hfinkel, xbolva00 Subscribers: JDevlieghere, hiraditya, llvm-commits Differential Revision: https://reviews.llvm.org/D46900 llvm-svn: 332466
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llvm
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@ -132,7 +132,18 @@ static bool isNonEscapingLocalObject(const Value *V) {
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/// Returns true if the pointer is one which would have been considered an
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/// escape by isNonEscapingLocalObject.
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static bool isEscapeSource(const Value *V) {
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if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
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if (auto CS = ImmutableCallSite(V)) {
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// launder_invariant_group captures its argument only by returning it,
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// so it might not be considered an escape by isNonEscapingLocalObject.
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// Note that adding similar special cases for intrinsics in CaptureTracking
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// requires handling them here too.
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if (CS.getIntrinsicID() == Intrinsic::launder_invariant_group)
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return false;
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return true;
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}
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if (isa<Argument>(V))
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return true;
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// The load case works because isNonEscapingLocalObject considers all
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@ -249,6 +249,8 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker) {
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// launder.invariant.group only captures pointer by returning it,
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// so the pointer wasn't captured if returned pointer is not captured.
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// Note that adding similar special cases for intrinsics requires handling
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// them in 'isEscapeSource' in BasicAA.
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if (CS.getIntrinsicID() == Intrinsic::launder_invariant_group) {
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AddUses(I);
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break;
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@ -0,0 +1,48 @@
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; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
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; RUN: opt < %s -basicaa -gvn -S | FileCheck -check-prefix=CHECK-GVN %s
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; The input *.ll had been adapted from bug 37458:
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;
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; struct A { virtual void f(); int n; };
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;
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; int h() {
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; A a;
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; a.n = 42;
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; return __builtin_launder(&a)->n;
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; }
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%struct.A = type <{ i8*, i8 }>
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; CHECK: testLaunderInvariantGroupIsNotEscapeSource
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; CHECK-GVN: testLaunderInvariantGroupIsNotEscapeSource
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define i8 @testLaunderInvariantGroupIsNotEscapeSource() {
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; CHECK-DAG: MustAlias: %struct.A* %a, i8* %a.bitcast
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; CHECK-DAG: PartialAlias: %struct.A* %a, i8* %n
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; CHECK-DAG: NoAlias: i8* %a.bitcast, i8* %n
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; CHECK-DAG: MustAlias: %struct.A* %a, i8* %a.laundered
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; CHECK-DAG: MustAlias: i8* %a.bitcast, i8* %a.laundered
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; CHECK-DAG: NoAlias: i8* %a.laundered, i8* %n
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; CHECK-DAG: PartialAlias: %struct.A* %a, i8* %n.laundered
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; CHECK-DAG: NoAlias: i8* %a.bitcast, i8* %n.laundered
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; CHECK-DAG: MustAlias: i8* %n, i8* %n.laundered
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; CHECK-DAG: NoAlias: i8* %a.laundered, i8* %n.laundered
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; CHECK-DAG: NoModRef: Ptr: %struct.A* %a <-> %a.laundered = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %a.bitcast)
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; CHECK-DAG: NoModRef: Ptr: i8* %a.bitcast <-> %a.laundered = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %a.bitcast)
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; CHECK-DAG: NoModRef: Ptr: i8* %n <-> %a.laundered = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %a.bitcast)
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; CHECK-DAG: NoModRef: Ptr: i8* %a.laundered <-> %a.laundered = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %a.bitcast)
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; CHECK-DAG: NoModRef: Ptr: i8* %n.laundered <-> %a.laundered = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %a.bitcast)
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entry:
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%a = alloca %struct.A, align 8
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%a.bitcast = bitcast %struct.A* %a to i8*
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%n = getelementptr inbounds %struct.A, %struct.A* %a, i64 0, i32 1
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store i8 42, i8* %n
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%a.laundered = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %a.bitcast)
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%n.laundered = getelementptr inbounds i8, i8* %a.laundered, i64 8
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%v = load i8, i8* %n.laundered
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; make sure that the load from %n.laundered to %v aliases the store of 42 to %n
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; CHECK-GVN: ret i8 42
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ret i8 %v
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}
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declare i8* @llvm.launder.invariant.group.p0i8(i8*)
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