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Simplify recursive launder.invariant.group and strip
Summary:
This patch is crucial for proving equality laundered/stripped
pointers. eg:
bool foo(A *a) {
return a == std::launder(a);
}
Clang with -fstrict-vtable-pointers will emit something like:
define dso_local zeroext i1 @_Z3fooP1A(%struct.A* %a) {
entry:
%c = bitcast %struct.A* %a to i8*
%call = tail call i8* @llvm.launder.invariant.group.p0i8(i8* %c)
%0 = bitcast %struct.A* %a to i8*
%1 = tail call i8* @llvm.strip.invariant.group.p0i8(i8* %0)
%2 = tail call i8* @llvm.strip.invariant.group.p0i8(i8* %call)
%cmp = icmp eq i8* %1, %2
ret i1 %cmp
}
and because %2 can be replaced with @llvm.strip.invariant.group(%0)
and that %2 and %1 will produce the same value (because strip is readnone)
we can replace compare with true.
Reviewers: rsmith, hfinkel, majnemer, amharc, kuhar
Subscribers: llvm-commits, hiraditya
Differential Revision: https://reviews.llvm.org/D47423
llvm-svn: 336963
This commit is contained in:
Piotr Padlewski
parent
bcf4db053e
commit
c64e878f84
@ -1266,6 +1266,40 @@ static Instruction *simplifyMaskedGather(IntrinsicInst &II, InstCombiner &IC) {
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return nullptr;
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}
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/// This function transforms launder.invariant.group and strip.invariant.group
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/// like:
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/// launder(launder(%x)) -> launder(%x) (the result is not the argument)
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/// launder(strip(%x)) -> launder(%x)
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/// strip(strip(%x)) -> strip(%x) (the result is not the argument)
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/// strip(launder(%x)) -> strip(%x)
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/// This is legal because it preserves the most recent information about
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/// the presence or absence of invariant.group.
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static Instruction *simplifyInvariantGroupIntrinsic(IntrinsicInst &II,
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InstCombiner &IC) {
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auto *Arg = II.getArgOperand(0);
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auto *StrippedArg = Arg->stripPointerCasts();
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auto *StrippedInvariantGroupsArg = Arg->stripPointerCastsAndInvariantGroups();
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if (StrippedArg == StrippedInvariantGroupsArg)
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return nullptr; // No launders/strips to remove.
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Value *Result = nullptr;
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if (II.getIntrinsicID() == Intrinsic::launder_invariant_group)
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Result = IC.Builder.CreateLaunderInvariantGroup(StrippedInvariantGroupsArg);
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else if (II.getIntrinsicID() == Intrinsic::strip_invariant_group)
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Result = IC.Builder.CreateStripInvariantGroup(StrippedInvariantGroupsArg);
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else
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llvm_unreachable(
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"simplifyInvariantGroupIntrinsic only handles launder and strip");
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if (Result->getType()->getPointerAddressSpace() !=
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II.getType()->getPointerAddressSpace())
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Result = IC.Builder.CreateAddrSpaceCast(Result, II.getType());
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if (Result->getType() != II.getType())
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Result = IC.Builder.CreateBitCast(Result, II.getType());
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return cast<Instruction>(Result);
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}
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static Instruction *simplifyMaskedScatter(IntrinsicInst &II, InstCombiner &IC) {
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// If the mask is all zeros, a scatter does nothing.
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auto *ConstMask = dyn_cast<Constant>(II.getArgOperand(3));
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@ -1940,7 +1974,11 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
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return simplifyMaskedGather(*II, *this);
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case Intrinsic::masked_scatter:
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return simplifyMaskedScatter(*II, *this);
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case Intrinsic::launder_invariant_group:
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case Intrinsic::strip_invariant_group:
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if (auto *SkippedBarrier = simplifyInvariantGroupIntrinsic(*II, *this))
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return replaceInstUsesWith(*II, SkippedBarrier);
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break;
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case Intrinsic::powi:
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if (ConstantInt *Power = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
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// 0 and 1 are handled in instsimplify
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@ -2,9 +2,8 @@
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; CHECK-LABEL: define void @checkNonnullLaunder()
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define void @checkNonnullLaunder() {
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; CHECK: %p = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %0)
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; CHECK: %p2 = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %p)
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; CHECK: call void @use(i8* nonnull %p2)
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; CHECK: %[[p:.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %0)
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; CHECK: call void @use(i8* nonnull %[[p]])
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entry:
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%0 = alloca i8, align 8
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@ -17,9 +16,8 @@ entry:
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; CHECK-LABEL: define void @checkNonnullStrip()
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define void @checkNonnullStrip() {
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; CHECK: %p = call i8* @llvm.strip.invariant.group.p0i8(i8* nonnull %0)
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; CHECK: %p2 = call i8* @llvm.strip.invariant.group.p0i8(i8* nonnull %p)
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; CHECK: call void @use(i8* nonnull %p2)
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; CHECK: %[[p:.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* nonnull %0)
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; CHECK: call void @use(i8* nonnull %[[p]])
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entry:
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%0 = alloca i8, align 8
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@ -1,4 +1,4 @@
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; RUN: opt -instcombine -S < %s | FileCheck %s
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; RUN: opt -instcombine -early-cse -S < %s | FileCheck %s
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; CHECK-LABEL: define i8* @simplifyNullLaunder()
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@ -37,10 +37,6 @@ define i8 addrspace(42)* @simplifyUndefLaunder2() {
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ret i8 addrspace(42)* %b2
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}
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declare i8* @llvm.launder.invariant.group.p0i8(i8*)
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declare i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)*)
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; CHECK-LABEL: define i8* @simplifyNullStrip()
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define i8* @simplifyNullStrip() {
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; CHECK-NEXT: ret i8* null
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@ -77,7 +73,78 @@ define i8 addrspace(42)* @simplifyUndefStrip2() {
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ret i8 addrspace(42)* %b2
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}
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; CHECK-LABEL: define i8* @simplifyLaunderOfLaunder(
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define i8* @simplifyLaunderOfLaunder(i8* %a) {
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; CHECK: call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
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; CHECK-NOT: llvm.launder.invariant.group
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%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
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%a3 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a2)
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ret i8* %a3
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}
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; CHECK-LABEL: define i8* @simplifyStripOfLaunder(
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define i8* @simplifyStripOfLaunder(i8* %a) {
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; CHECK-NOT: llvm.launder.invariant.group
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; CHECK: call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
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%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
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%a3 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a2)
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ret i8* %a3
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}
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; CHECK-LABEL: define i1 @simplifyForCompare(
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define i1 @simplifyForCompare(i8* %a) {
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%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
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%a3 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a2)
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%b2 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
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%c = icmp eq i8* %a3, %b2
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; CHECK: ret i1 true
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ret i1 %c
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}
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; CHECK-LABEL: define i16* @skipWithDifferentTypes(
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define i16* @skipWithDifferentTypes(i8* %a) {
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%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
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%c1 = bitcast i8* %a2 to i16*
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; CHECK: %[[b:.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
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%a3 = call i16* @llvm.strip.invariant.group.p0i16(i16* %c1)
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; CHECK-NEXT: %[[r:.*]] = bitcast i8* %[[b]] to i16*
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; CHECK-NEXT: ret i16* %[[r]]
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ret i16* %a3
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}
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; CHECK-LABEL: define i16 addrspace(42)* @skipWithDifferentTypesAddrspace(
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define i16 addrspace(42)* @skipWithDifferentTypesAddrspace(i8 addrspace(42)* %a) {
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%a2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* %a)
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%c1 = bitcast i8 addrspace(42)* %a2 to i16 addrspace(42)*
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; CHECK: %[[b:.*]] = call i8 addrspace(42)* @llvm.strip.invariant.group.p42i8(i8 addrspace(42)* %a)
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%a3 = call i16 addrspace(42)* @llvm.strip.invariant.group.p42i16(i16 addrspace(42)* %c1)
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; CHECK-NEXT: %[[r:.*]] = bitcast i8 addrspace(42)* %[[b]] to i16 addrspace(42)*
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; CHECK-NEXT: ret i16 addrspace(42)* %[[r]]
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ret i16 addrspace(42)* %a3
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}
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; CHECK-LABEL: define i16 addrspace(42)* @skipWithDifferentTypesDifferentAddrspace(
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define i16 addrspace(42)* @skipWithDifferentTypesDifferentAddrspace(i8* %a) {
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%cast = addrspacecast i8* %a to i8 addrspace(42)*
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%a2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* %cast)
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%c1 = bitcast i8 addrspace(42)* %a2 to i16 addrspace(42)*
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; CHECK: %[[b:.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
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%a3 = call i16 addrspace(42)* @llvm.strip.invariant.group.p42i16(i16 addrspace(42)* %c1)
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; CHECK-NEXT: %[[r:.*]] = bitcast i8* %[[b]] to i16*
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; CHECK-NEXT: %[[r2:.*]] = addrspacecast i16* %[[r]] to i16 addrspace(42)*
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; CHECK-NEXT: ret i16 addrspace(42)* %[[r2]]
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ret i16 addrspace(42)* %a3
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}
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declare i8* @llvm.launder.invariant.group.p0i8(i8*)
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declare i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)*)
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declare i8* @llvm.strip.invariant.group.p0i8(i8*)
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declare i8 addrspace(42)* @llvm.strip.invariant.group.p42i8(i8 addrspace(42)*)
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declare i16* @llvm.strip.invariant.group.p0i16(i16* %c1)
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declare i16 addrspace(42)* @llvm.strip.invariant.group.p42i16(i16 addrspace(42)* %c1)
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attributes #0 = { "null-pointer-is-valid"="true" }
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