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[InstCombine] Combine ptrauth constants into ptrauth intrinsics. #94705

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merged 3 commits into from
Jun 27, 2024
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[InstCombine] Combine ptrauth constants into ptrauth intrinsics. #94705

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9dfe010
[InstCombine] Combine ptrauth constants into ptrauth intrinsics.
ahmedbougacha Sep 27, 2021
4943d02
Replace typed pointers in casts with ptr.
ahmedbougacha Jun 13, 2024
b08be11
Address review feedback.
ahmedbougacha Jun 27, 2024
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27 changes: 24 additions & 3 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2643,13 +2643,14 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
// (sign|resign) + (auth|resign) can be folded by omitting the middle
// sign+auth component if the key and discriminator match.
bool NeedSign = II->getIntrinsicID() == Intrinsic::ptrauth_resign;
Value *Ptr = II->getArgOperand(0);
Value *Key = II->getArgOperand(1);
Value *Disc = II->getArgOperand(2);

// AuthKey will be the key we need to end up authenticating against in
// whatever we replace this sequence with.
Value *AuthKey = nullptr, *AuthDisc = nullptr, *BasePtr;
if (auto CI = dyn_cast<CallBase>(II->getArgOperand(0))) {
if (const auto *CI = dyn_cast<CallBase>(Ptr)) {
BasePtr = CI->getArgOperand(0);
if (CI->getIntrinsicID() == Intrinsic::ptrauth_sign) {
if (CI->getArgOperand(1) != Key || CI->getArgOperand(2) != Disc)
Expand All @@ -2661,6 +2662,27 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
AuthDisc = CI->getArgOperand(2);
} else
break;
} else if (const auto *PtrToInt = dyn_cast<PtrToIntOperator>(Ptr)) {
// ptrauth constants are equivalent to a call to @llvm.ptrauth.sign for
// our purposes, so check for that too.
const auto *CPA = dyn_cast<ConstantPtrAuth>(PtrToInt->getOperand(0));
if (!CPA || !CPA->isKnownCompatibleWith(Key, Disc, DL))
break;

// resign(ptrauth(p,ks,ds),ks,ds,kr,dr) -> ptrauth(p,kr,dr)
if (NeedSign && isa<ConstantInt>(II->getArgOperand(4))) {
auto *SignKey = cast<ConstantInt>(II->getArgOperand(3));
auto *SignDisc = cast<ConstantInt>(II->getArgOperand(4));
auto *SignAddrDisc = ConstantPointerNull::get(Builder.getPtrTy());
auto *NewCPA = ConstantPtrAuth::get(CPA->getPointer(), SignKey,
SignDisc, SignAddrDisc);
replaceInstUsesWith(
*II, ConstantExpr::getPointerCast(NewCPA, II->getType()));
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Is this getPointerCast() needed? If so, I think it's missing test coverage.

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Heh I thought this was another remnant of typed pointers, but this one is indeed needed, to reconcile the i64-centric ptrauth intrinsics with ptrs in ptr contexts elsewhere, i.e. the ptrtoint in:

; CHECK-NEXT:    ret i64 ptrtoint (ptr ptrauth (ptr @foo, i32 0, i64 42) to i64)

  %tmp0 = ptrtoint ptr %p to i64
  %authed = call i64 @llvm.ptrauth.resign(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234) to i64), i32 1, i64 1234, i32 0, i64 42)
  ret i64 %authed

return eraseInstFromFunction(*II);
}

// auth(ptrauth(p,k,d),k,d) -> p
BasePtr = Builder.CreatePtrToInt(CPA->getPointer(), II->getType());
} else
break;

Expand All @@ -2677,8 +2699,7 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
} else {
// sign(0) + auth(0) = nop
replaceInstUsesWith(*II, BasePtr);
eraseInstFromFunction(*II);
return nullptr;
return eraseInstFromFunction(*II);
}

SmallVector<Value *, 4> CallArgs;
Expand Down
74 changes: 74 additions & 0 deletions llvm/test/Transforms/InstCombine/ptrauth-intrinsics.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,27 @@ define i64 @test_ptrauth_nop(ptr %p) {
ret i64 %authed
}

declare void @foo()
declare void @bar()

define i64 @test_ptrauth_nop_constant() {
; CHECK-LABEL: @test_ptrauth_nop_constant(
; CHECK-NEXT: ret i64 ptrtoint (ptr @foo to i64)
;
%authed = call i64 @llvm.ptrauth.auth(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234) to i64), i32 1, i64 1234)
ret i64 %authed
}

define i64 @test_ptrauth_nop_constant_addrdisc() {
; CHECK-LABEL: @test_ptrauth_nop_constant_addrdisc(
; CHECK-NEXT: ret i64 ptrtoint (ptr @foo to i64)
;
%addr = ptrtoint ptr @foo to i64
%blended = call i64 @llvm.ptrauth.blend(i64 %addr, i64 1234)
%authed = call i64 @llvm.ptrauth.auth(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234, ptr @foo) to i64), i32 1, i64 %blended)
ret i64 %authed
}

define i64 @test_ptrauth_nop_mismatch(ptr %p) {
; CHECK-LABEL: @test_ptrauth_nop_mismatch(
; CHECK-NEXT: [[TMP0:%.*]] = ptrtoint ptr [[P:%.*]] to i64
Expand Down Expand Up @@ -87,6 +108,59 @@ define i64 @test_ptrauth_resign_auth_mismatch(ptr %p) {
ret i64 %authed
}

define i64 @test_ptrauth_nop_constant_mismatch() {
; CHECK-LABEL: @test_ptrauth_nop_constant_mismatch(
; CHECK-NEXT: [[AUTHED:%.*]] = call i64 @llvm.ptrauth.auth(i64 ptrtoint (ptr ptrauth (ptr @foo, i32 1, i64 1234) to i64), i32 1, i64 12)
; CHECK-NEXT: ret i64 [[AUTHED]]
;
%authed = call i64 @llvm.ptrauth.auth(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234) to i64), i32 1, i64 12)
ret i64 %authed
}

define i64 @test_ptrauth_nop_constant_mismatch_key() {
; CHECK-LABEL: @test_ptrauth_nop_constant_mismatch_key(
; CHECK-NEXT: [[AUTHED:%.*]] = call i64 @llvm.ptrauth.auth(i64 ptrtoint (ptr ptrauth (ptr @foo, i32 1, i64 1234) to i64), i32 0, i64 1234)
; CHECK-NEXT: ret i64 [[AUTHED]]
;
%authed = call i64 @llvm.ptrauth.auth(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234) to i64), i32 0, i64 1234)
ret i64 %authed
}

define i64 @test_ptrauth_nop_constant_addrdisc_mismatch() {
; CHECK-LABEL: @test_ptrauth_nop_constant_addrdisc_mismatch(
; CHECK-NEXT: [[BLENDED:%.*]] = call i64 @llvm.ptrauth.blend(i64 ptrtoint (ptr @foo to i64), i64 12)
; CHECK-NEXT: [[AUTHED:%.*]] = call i64 @llvm.ptrauth.auth(i64 ptrtoint (ptr ptrauth (ptr @foo, i32 1, i64 1234, ptr @foo) to i64), i32 1, i64 [[BLENDED]])
; CHECK-NEXT: ret i64 [[AUTHED]]
;
%addr = ptrtoint ptr @foo to i64
%blended = call i64 @llvm.ptrauth.blend(i64 %addr, i64 12)
%authed = call i64 @llvm.ptrauth.auth(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234, ptr @foo) to i64), i32 1, i64 %blended)
ret i64 %authed
}

define i64 @test_ptrauth_nop_constant_addrdisc_mismatch2() {
; CHECK-LABEL: @test_ptrauth_nop_constant_addrdisc_mismatch2(
; CHECK-NEXT: [[BLENDED:%.*]] = call i64 @llvm.ptrauth.blend(i64 ptrtoint (ptr @bar to i64), i64 1234)
; CHECK-NEXT: [[AUTHED:%.*]] = call i64 @llvm.ptrauth.auth(i64 ptrtoint (ptr ptrauth (ptr @foo, i32 1, i64 1234, ptr @foo) to i64), i32 1, i64 [[BLENDED]])
; CHECK-NEXT: ret i64 [[AUTHED]]
;
%addr = ptrtoint ptr @bar to i64
%blended = call i64 @llvm.ptrauth.blend(i64 %addr, i64 1234)
%authed = call i64 @llvm.ptrauth.auth(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234, ptr @foo) to i64), i32 1, i64 %blended)
ret i64 %authed
}

define i64 @test_ptrauth_resign_ptrauth_constant(ptr %p) {
; CHECK-LABEL: @test_ptrauth_resign_ptrauth_constant(
; CHECK-NEXT: ret i64 ptrtoint (ptr ptrauth (ptr @foo, i32 0, i64 42) to i64)
;

%tmp0 = ptrtoint ptr %p to i64
%authed = call i64 @llvm.ptrauth.resign(i64 ptrtoint(ptr ptrauth(ptr @foo, i32 1, i64 1234) to i64), i32 1, i64 1234, i32 0, i64 42)
ret i64 %authed
}

declare i64 @llvm.ptrauth.auth(i64, i32, i64)
declare i64 @llvm.ptrauth.sign(i64, i32, i64)
declare i64 @llvm.ptrauth.resign(i64, i32, i64, i32, i64)
declare i64 @llvm.ptrauth.blend(i64, i64)
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