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 2018-07-12 23:55:20 +00:00
parent c379d1a424
commit c63b492bcd
3 changed files with 115 additions and 12 deletions

View File

@ -1266,6 +1266,40 @@ static Instruction *simplifyMaskedGather(IntrinsicInst &II, InstCombiner &IC) {
return nullptr;
}
/// This function transforms launder.invariant.group and strip.invariant.group
/// like:
/// launder(launder(%x)) -> launder(%x) (the result is not the argument)
/// launder(strip(%x)) -> launder(%x)
/// strip(strip(%x)) -> strip(%x) (the result is not the argument)
/// strip(launder(%x)) -> strip(%x)
/// This is legal because it preserves the most recent information about
/// the presence or absence of invariant.group.
static Instruction *simplifyInvariantGroupIntrinsic(IntrinsicInst &II,
InstCombiner &IC) {
auto *Arg = II.getArgOperand(0);
auto *StrippedArg = Arg->stripPointerCasts();
auto *StrippedInvariantGroupsArg = Arg->stripPointerCastsAndInvariantGroups();
if (StrippedArg == StrippedInvariantGroupsArg)
return nullptr; // No launders/strips to remove.
Value *Result = nullptr;
if (II.getIntrinsicID() == Intrinsic::launder_invariant_group)
Result = IC.Builder.CreateLaunderInvariantGroup(StrippedInvariantGroupsArg);
else if (II.getIntrinsicID() == Intrinsic::strip_invariant_group)
Result = IC.Builder.CreateStripInvariantGroup(StrippedInvariantGroupsArg);
else
llvm_unreachable(
"simplifyInvariantGroupIntrinsic only handles launder and strip");
if (Result->getType()->getPointerAddressSpace() !=
II.getType()->getPointerAddressSpace())
Result = IC.Builder.CreateAddrSpaceCast(Result, II.getType());
if (Result->getType() != II.getType())
Result = IC.Builder.CreateBitCast(Result, II.getType());
return cast<Instruction>(Result);
}
static Instruction *simplifyMaskedScatter(IntrinsicInst &II, InstCombiner &IC) {
// If the mask is all zeros, a scatter does nothing.
auto *ConstMask = dyn_cast<Constant>(II.getArgOperand(3));
@ -1940,7 +1974,11 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
return simplifyMaskedGather(*II, *this);
case Intrinsic::masked_scatter:
return simplifyMaskedScatter(*II, *this);
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
if (auto *SkippedBarrier = simplifyInvariantGroupIntrinsic(*II, *this))
return replaceInstUsesWith(*II, SkippedBarrier);
break;
case Intrinsic::powi:
if (ConstantInt *Power = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
// 0 and 1 are handled in instsimplify

View File

@ -2,9 +2,8 @@
; CHECK-LABEL: define void @checkNonnullLaunder()
define void @checkNonnullLaunder() {
; CHECK: %p = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %0)
; CHECK: %p2 = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %p)
; CHECK: call void @use(i8* nonnull %p2)
; CHECK: %[[p:.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %0)
; CHECK: call void @use(i8* nonnull %[[p]])
entry:
%0 = alloca i8, align 8
@ -17,9 +16,8 @@ entry:
; CHECK-LABEL: define void @checkNonnullStrip()
define void @checkNonnullStrip() {
; CHECK: %p = call i8* @llvm.strip.invariant.group.p0i8(i8* nonnull %0)
; CHECK: %p2 = call i8* @llvm.strip.invariant.group.p0i8(i8* nonnull %p)
; CHECK: call void @use(i8* nonnull %p2)
; CHECK: %[[p:.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* nonnull %0)
; CHECK: call void @use(i8* nonnull %[[p]])
entry:
%0 = alloca i8, align 8

View File

@ -1,4 +1,4 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; RUN: opt -instcombine -early-cse -S < %s | FileCheck %s
; CHECK-LABEL: define i8* @simplifyNullLaunder()
@ -37,10 +37,6 @@ define i8 addrspace(42)* @simplifyUndefLaunder2() {
ret i8 addrspace(42)* %b2
}
declare i8* @llvm.launder.invariant.group.p0i8(i8*)
declare i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)*)
; CHECK-LABEL: define i8* @simplifyNullStrip()
define i8* @simplifyNullStrip() {
; CHECK-NEXT: ret i8* null
@ -77,7 +73,78 @@ define i8 addrspace(42)* @simplifyUndefStrip2() {
ret i8 addrspace(42)* %b2
}
; CHECK-LABEL: define i8* @simplifyLaunderOfLaunder(
define i8* @simplifyLaunderOfLaunder(i8* %a) {
; CHECK: call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
; CHECK-NOT: llvm.launder.invariant.group
%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
%a3 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a2)
ret i8* %a3
}
; CHECK-LABEL: define i8* @simplifyStripOfLaunder(
define i8* @simplifyStripOfLaunder(i8* %a) {
; CHECK-NOT: llvm.launder.invariant.group
; CHECK: call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
%a3 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a2)
ret i8* %a3
}
; CHECK-LABEL: define i1 @simplifyForCompare(
define i1 @simplifyForCompare(i8* %a) {
%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
%a3 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a2)
%b2 = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
%c = icmp eq i8* %a3, %b2
; CHECK: ret i1 true
ret i1 %c
}
; CHECK-LABEL: define i16* @skipWithDifferentTypes(
define i16* @skipWithDifferentTypes(i8* %a) {
%a2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %a)
%c1 = bitcast i8* %a2 to i16*
; CHECK: %[[b:.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
%a3 = call i16* @llvm.strip.invariant.group.p0i16(i16* %c1)
; CHECK-NEXT: %[[r:.*]] = bitcast i8* %[[b]] to i16*
; CHECK-NEXT: ret i16* %[[r]]
ret i16* %a3
}
; CHECK-LABEL: define i16 addrspace(42)* @skipWithDifferentTypesAddrspace(
define i16 addrspace(42)* @skipWithDifferentTypesAddrspace(i8 addrspace(42)* %a) {
%a2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* %a)
%c1 = bitcast i8 addrspace(42)* %a2 to i16 addrspace(42)*
; CHECK: %[[b:.*]] = call i8 addrspace(42)* @llvm.strip.invariant.group.p42i8(i8 addrspace(42)* %a)
%a3 = call i16 addrspace(42)* @llvm.strip.invariant.group.p42i16(i16 addrspace(42)* %c1)
; CHECK-NEXT: %[[r:.*]] = bitcast i8 addrspace(42)* %[[b]] to i16 addrspace(42)*
; CHECK-NEXT: ret i16 addrspace(42)* %[[r]]
ret i16 addrspace(42)* %a3
}
; CHECK-LABEL: define i16 addrspace(42)* @skipWithDifferentTypesDifferentAddrspace(
define i16 addrspace(42)* @skipWithDifferentTypesDifferentAddrspace(i8* %a) {
%cast = addrspacecast i8* %a to i8 addrspace(42)*
%a2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* %cast)
%c1 = bitcast i8 addrspace(42)* %a2 to i16 addrspace(42)*
; CHECK: %[[b:.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* %a)
%a3 = call i16 addrspace(42)* @llvm.strip.invariant.group.p42i16(i16 addrspace(42)* %c1)
; CHECK-NEXT: %[[r:.*]] = bitcast i8* %[[b]] to i16*
; CHECK-NEXT: %[[r2:.*]] = addrspacecast i16* %[[r]] to i16 addrspace(42)*
; CHECK-NEXT: ret i16 addrspace(42)* %[[r2]]
ret i16 addrspace(42)* %a3
}
declare i8* @llvm.launder.invariant.group.p0i8(i8*)
declare i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)*)
declare i8* @llvm.strip.invariant.group.p0i8(i8*)
declare i8 addrspace(42)* @llvm.strip.invariant.group.p42i8(i8 addrspace(42)*)
declare i16* @llvm.strip.invariant.group.p0i16(i16* %c1)
declare i16 addrspace(42)* @llvm.strip.invariant.group.p42i16(i16 addrspace(42)* %c1)
attributes #0 = { "null-pointer-is-valid"="true" }