Basic MTE stack tagging instrumentation.

Summary:
Use MTE intrinsics to tag stack variables in functions with
sanitize_memtag attribute.

Reviewers: pcc, vitalybuka, hctim, ostannard

Subscribers: srhines, mgorny, javed.absar, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64173

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@366361 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AArch64/AArch64.h b/lib/Target/AArch64/AArch64.h
index 2e63e261c489acbaa0f985a93601be15d7d877bf..6965403a25ab9377caa5580bb51474de1383429d 100644 (file)
--- a/lib/Target/AArch64/AArch64.h
+++ b/lib/Target/AArch64/AArch64.h
@@ -56,6 +56,7 @@ InstructionSelector *
 createAArch64InstructionSelector(const AArch64TargetMachine &,
                                  AArch64Subtarget &, AArch64RegisterBankInfo &);
 FunctionPass *createAArch64PreLegalizeCombiner();
+FunctionPass *createAArch64StackTaggingPass();
 
 void initializeAArch64A53Fix835769Pass(PassRegistry&);
 void initializeAArch64A57FPLoadBalancingPass(PassRegistry&);
@@ -78,6 +79,7 @@ void initializeAArch64StorePairSuppressPass(PassRegistry&);
 void initializeFalkorHWPFFixPass(PassRegistry&);
 void initializeFalkorMarkStridedAccessesLegacyPass(PassRegistry&);
 void initializeLDTLSCleanupPass(PassRegistry&);
+void initializeAArch64StackTaggingPass(PassRegistry&);
 } // end namespace llvm
 
 #endif

diff --git a/lib/Target/AArch64/AArch64StackTagging.cpp b/lib/Target/AArch64/AArch64StackTagging.cpp
new file mode 100644 (file)
index 0000000..f27a631
--- /dev/null
+++ b/lib/Target/AArch64/AArch64StackTagging.cpp
@@ -0,0 +1,345 @@
+//===- AArch64StackTagging.cpp - Stack tagging in IR --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
+
+#include "AArch64.h"
+#include "AArch64InstrInfo.h"
+#include "AArch64Subtarget.h"
+#include "AArch64TargetMachine.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/None.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/ScalarEvolutionExpressions.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/CodeGen/LiveRegUnits.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetPassConfig.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/IR/DebugLoc.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include <cassert>
+#include <iterator>
+#include <utility>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "stack-tagging"
+
+static constexpr unsigned kTagGranuleSize = 16;
+
+namespace {
+class AArch64StackTagging : public FunctionPass {
+  struct AllocaInfo {
+    AllocaInst *AI;
+    SmallVector<IntrinsicInst *, 2> LifetimeStart;
+    SmallVector<IntrinsicInst *, 2> LifetimeEnd;
+    SmallVector<DbgVariableIntrinsic *, 2> DbgVariableIntrinsics;
+    int Tag; // -1 for non-tagged allocations
+  };
+
+public:
+  static char ID; // Pass ID, replacement for typeid
+
+  AArch64StackTagging() : FunctionPass(ID) {
+    initializeAArch64StackTaggingPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool isInterestingAlloca(const AllocaInst &AI);
+  void alignAndPadAlloca(AllocaInfo &Info);
+
+  void tagAlloca(AllocaInst *AI, Instruction *InsertBefore, Value *Ptr,
+                 uint64_t Size);
+  void untagAlloca(AllocaInst *AI, Instruction *InsertBefore, uint64_t Size);
+
+  Instruction *
+  insertBaseTaggedPointer(const MapVector<AllocaInst *, AllocaInfo> &Allocas,
+                          const DominatorTree *DT);
+  bool runOnFunction(Function &F) override;
+
+  StringRef getPassName() const override { return "AArch64 Stack Tagging"; }
+
+private:
+  Function *F;
+  Function *SetTagFunc;
+  const DataLayout *DL;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+  }
+};
+
+} // end anonymous namespace
+
+char AArch64StackTagging::ID = 0;
+
+INITIALIZE_PASS_BEGIN(AArch64StackTagging, DEBUG_TYPE, "AArch64 Stack Tagging",
+                      false, false)
+INITIALIZE_PASS_END(AArch64StackTagging, DEBUG_TYPE, "AArch64 Stack Tagging",
+                    false, false)
+
+FunctionPass *llvm::createAArch64StackTaggingPass() {
+  return new AArch64StackTagging();
+}
+
+bool AArch64StackTagging::isInterestingAlloca(const AllocaInst &AI) {
+  // FIXME: support dynamic allocas
+  bool IsInteresting =
+      AI.getAllocatedType()->isSized() && AI.isStaticAlloca() &&
+      // alloca() may be called with 0 size, ignore it.
+      AI.getAllocationSizeInBits(*DL).getValue() > 0 &&
+      // inalloca allocas are not treated as static, and we don't want
+      // dynamic alloca instrumentation for them as well.
+      !AI.isUsedWithInAlloca() &&
+      // swifterror allocas are register promoted by ISel
+      !AI.isSwiftError();
+  return IsInteresting;
+}
+
+void AArch64StackTagging::tagAlloca(AllocaInst *AI, Instruction *InsertBefore,
+                                    Value *Ptr, uint64_t Size) {
+  IRBuilder<> IRB(InsertBefore);
+  IRB.CreateCall(SetTagFunc, {Ptr, ConstantInt::get(IRB.getInt64Ty(), Size)});
+}
+
+void AArch64StackTagging::untagAlloca(AllocaInst *AI, Instruction *InsertBefore,
+                                      uint64_t Size) {
+  IRBuilder<> IRB(InsertBefore);
+  IRB.CreateCall(SetTagFunc, {IRB.CreatePointerCast(AI, IRB.getInt8PtrTy()),
+                              ConstantInt::get(IRB.getInt64Ty(), Size)});
+}
+
+Instruction *AArch64StackTagging::insertBaseTaggedPointer(
+    const MapVector<AllocaInst *, AllocaInfo> &Allocas,
+    const DominatorTree *DT) {
+  BasicBlock *PrologueBB = nullptr;
+  // Try sinking IRG as deep as possible to avoid hurting shrink wrap.
+  for (auto &I : Allocas) {
+    const AllocaInfo &Info = I.second;
+    AllocaInst *AI = Info.AI;
+    if (Info.Tag < 0)
+      continue;
+    if (!PrologueBB) {
+      PrologueBB = AI->getParent();
+      continue;
+    }
+    PrologueBB = DT->findNearestCommonDominator(PrologueBB, AI->getParent());
+  }
+  assert(PrologueBB);
+
+  IRBuilder<> IRB(&PrologueBB->front());
+  Function *IRG_SP =
+      Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_irg_sp);
+  Instruction *Base =
+      IRB.CreateCall(IRG_SP, {Constant::getNullValue(IRB.getInt64Ty())});
+  Base->setName("basetag");
+  return Base;
+}
+
+void AArch64StackTagging::alignAndPadAlloca(AllocaInfo &Info) {
+  unsigned NewAlignment = std::max(Info.AI->getAlignment(), kTagGranuleSize);
+  Info.AI->setAlignment(NewAlignment);
+
+  uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
+  uint64_t AlignedSize = alignTo(Size, kTagGranuleSize);
+  if (Size == AlignedSize)
+    return;
+
+  // Add padding to the alloca.
+  Type *AllocatedType =
+      Info.AI->isArrayAllocation()
+          ? ArrayType::get(
+                Info.AI->getAllocatedType(),
+                dyn_cast<ConstantInt>(Info.AI->getArraySize())->getZExtValue())
+          : Info.AI->getAllocatedType();
+  Type *PaddingType =
+      ArrayType::get(Type::getInt8Ty(F->getContext()), AlignedSize - Size);
+  Type *TypeWithPadding = StructType::get(AllocatedType, PaddingType);
+  auto *NewAI = new AllocaInst(
+      TypeWithPadding, Info.AI->getType()->getAddressSpace(), nullptr, "", Info.AI);
+  NewAI->takeName(Info.AI);
+  NewAI->setAlignment(Info.AI->getAlignment());
+  NewAI->setUsedWithInAlloca(Info.AI->isUsedWithInAlloca());
+  NewAI->setSwiftError(Info.AI->isSwiftError());
+  NewAI->copyMetadata(*Info.AI);
+
+  auto *NewPtr = new BitCastInst(NewAI, Info.AI->getType(), "", Info.AI);
+  Info.AI->replaceAllUsesWith(NewPtr);
+  Info.AI->eraseFromParent();
+  Info.AI = NewAI;
+}
+
+// FIXME: check for MTE extension
+bool AArch64StackTagging::runOnFunction(Function &Fn) {
+  if (!Fn.hasFnAttribute(Attribute::SanitizeMemTag))
+    return false;
+
+  F = &Fn;
+  DL = &Fn.getParent()->getDataLayout();
+
+  MapVector<AllocaInst *, AllocaInfo> Allocas; // need stable iteration order
+  SmallVector<Instruction *, 8> RetVec;
+  DenseMap<Value *, AllocaInst *> AllocaForValue;
+  SmallVector<Instruction *, 4> UnrecognizedLifetimes;
+
+  for (auto &BB : *F) {
+    for (BasicBlock::iterator IT = BB.begin(); IT != BB.end(); ++IT) {
+      Instruction *I = &*IT;
+      if (auto *AI = dyn_cast<AllocaInst>(I)) {
+        Allocas[AI].AI = AI;
+        continue;
+      }
+
+      if (auto *DVI = dyn_cast<DbgVariableIntrinsic>(I)) {
+        if (auto *AI =
+                dyn_cast_or_null<AllocaInst>(DVI->getVariableLocation())) {
+          Allocas[AI].DbgVariableIntrinsics.push_back(DVI);
+        }
+        continue;
+      }
+
+      auto *II = dyn_cast<IntrinsicInst>(I);
+      if (II && (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+                 II->getIntrinsicID() == Intrinsic::lifetime_end)) {
+        AllocaInst *AI =
+            llvm::findAllocaForValue(II->getArgOperand(1), AllocaForValue);
+        if (!AI) {
+          UnrecognizedLifetimes.push_back(I);
+          continue;
+        }
+        if (II->getIntrinsicID() == Intrinsic::lifetime_start)
+          Allocas[AI].LifetimeStart.push_back(II);
+        else
+          Allocas[AI].LifetimeEnd.push_back(II);
+      }
+
+      if (isa<ReturnInst>(I) || isa<ResumeInst>(I) || isa<CleanupReturnInst>(I))
+        RetVec.push_back(I);
+    }
+  }
+
+  if (Allocas.empty())
+    return false;
+
+  int NextTag = 0;
+  int NumInterestingAllocas = 0;
+  for (auto &I : Allocas) {
+    AllocaInfo &Info = I.second;
+    assert(Info.AI);
+
+    if (!isInterestingAlloca(*Info.AI)) {
+      Info.Tag = -1;
+      continue;
+    }
+
+    alignAndPadAlloca(Info);
+    NumInterestingAllocas++;
+    Info.Tag = NextTag;
+    NextTag = (NextTag + 1) % 16;
+  }
+
+  if (NumInterestingAllocas == 0)
+    return true;
+
+  SetTagFunc =
+      Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_settag);
+
+  // Compute DT only if the function has the attribute, there are more than 1
+  // interesting allocas, and it is not available for free.
+  Instruction *Base;
+  if (NumInterestingAllocas > 1) {
+    auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
+    if (DTWP) {
+      Base = insertBaseTaggedPointer(Allocas, &DTWP->getDomTree());
+    } else {
+      DominatorTree DT(*F);
+      Base = insertBaseTaggedPointer(Allocas, &DT);
+    }
+  } else {
+    Base = insertBaseTaggedPointer(Allocas, nullptr);
+  }
+
+  for (auto &I : Allocas) {
+    const AllocaInfo &Info = I.second;
+    AllocaInst *AI = Info.AI;
+    if (Info.Tag < 0)
+      continue;
+
+    // Replace alloca with tagp(alloca).
+    IRBuilder<> IRB(Info.AI->getNextNode());
+    Function *TagP = Intrinsic::getDeclaration(
+        F->getParent(), Intrinsic::aarch64_tagp, {Info.AI->getType()});
+    Instruction *TagPCall =
+        IRB.CreateCall(TagP, {Constant::getNullValue(Info.AI->getType()), Base,
+                              ConstantInt::get(IRB.getInt64Ty(), Info.Tag)});
+    if (Info.AI->hasName())
+      TagPCall->setName(Info.AI->getName() + ".tag");
+    Info.AI->replaceAllUsesWith(TagPCall);
+    TagPCall->setOperand(0, Info.AI);
+
+    if (UnrecognizedLifetimes.empty() && Info.LifetimeStart.size() == 1 &&
+        Info.LifetimeEnd.size() == 1) {
+      IntrinsicInst *Start = Info.LifetimeStart[0];
+      uint64_t Size =
+          dyn_cast<ConstantInt>(Start->getArgOperand(0))->getZExtValue();
+      Size = alignTo(Size, kTagGranuleSize);
+      tagAlloca(AI, Start->getNextNode(), Start->getArgOperand(1), Size);
+      untagAlloca(AI, Info.LifetimeEnd[0], Size);
+    } else {
+      uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
+      tagAlloca(AI, TagPCall->getNextNode(),
+                IRB.CreatePointerCast(TagPCall, IRB.getInt8PtrTy()), Size);
+      for (auto &RI : RetVec) {
+        untagAlloca(AI, RI, Size);
+      }
+      // We may have inserted tag/untag outside of any lifetime interval.
+      // Remove all lifetime intrinsics for this alloca.
+      for (auto &II : Info.LifetimeStart)
+        II->eraseFromParent();
+      for (auto &II : Info.LifetimeEnd)
+        II->eraseFromParent();
+    }
+
+    // Fixup debug intrinsics to point to the new alloca.
+    for (auto DVI : Info.DbgVariableIntrinsics)
+      DVI->setArgOperand(
+          0,
+          MetadataAsValue::get(F->getContext(), LocalAsMetadata::get(Info.AI)));
+  }
+
+  // If we have instrumented at least one alloca, all unrecognized lifetime
+  // instrinsics have to go.
+  for (auto &I : UnrecognizedLifetimes)
+    I->eraseFromParent();
+
+  return true;
+}

diff --git a/lib/Target/AArch64/AArch64TargetMachine.cpp b/lib/Target/AArch64/AArch64TargetMachine.cpp
index 7ae055ad503636e753ce492b7d7aeae74b79ebc3..86546148049977fcc96fbfda347b429cfcf11b52 100644 (file)
--- a/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -179,6 +179,7 @@ extern "C" void LLVMInitializeAArch64Target() {
   initializeFalkorMarkStridedAccessesLegacyPass(*PR);
   initializeLDTLSCleanupPass(*PR);
   initializeAArch64SpeculationHardeningPass(*PR);
+  initializeAArch64StackTaggingPass(*PR);
 }
 
 //===----------------------------------------------------------------------===//
@@ -446,6 +447,8 @@ void AArch64PassConfig::addIRPasses() {
     // invariant.
     addPass(createLICMPass());
   }
+
+  addPass(createAArch64StackTaggingPass());
 }
 
 // Pass Pipeline Configuration

diff --git a/lib/Target/AArch64/CMakeLists.txt b/lib/Target/AArch64/CMakeLists.txt
index 0fdf8e3d534203dee70bc17de237f0462a97f18d..3154ed03bd46df5907a107a939d2107f817c7887 100644 (file)
--- a/lib/Target/AArch64/CMakeLists.txt
+++ b/lib/Target/AArch64/CMakeLists.txt
@@ -55,6 +55,7 @@ add_llvm_target(AArch64CodeGen
   AArch64RegisterInfo.cpp
   AArch64SelectionDAGInfo.cpp
   AArch64SpeculationHardening.cpp
+  AArch64StackTagging.cpp
   AArch64StorePairSuppress.cpp
   AArch64Subtarget.cpp
   AArch64TargetMachine.cpp

diff --git a/test/CodeGen/AArch64/O0-pipeline.ll b/test/CodeGen/AArch64/O0-pipeline.ll
index b25d4e94e3e1e86b93c67ea233585f6c6a1994f0..e8f831f6151e2c93cfc24421d94edcc8f9400e2e 100644 (file)
--- a/test/CodeGen/AArch64/O0-pipeline.ll
+++ b/test/CodeGen/AArch64/O0-pipeline.ll
@@ -25,6 +25,7 @@
 ; CHECK-NEXT:       Instrument function entry/exit with calls to e.g. mcount() (post inlining)
 ; CHECK-NEXT:       Scalarize Masked Memory Intrinsics
 ; CHECK-NEXT:       Expand reduction intrinsics
+; CHECK-NEXT:       AArch64 Stack Tagging
 ; CHECK-NEXT:     Rewrite Symbols
 ; CHECK-NEXT:     FunctionPass Manager
 ; CHECK-NEXT:       Dominator Tree Construction

diff --git a/test/CodeGen/AArch64/O3-pipeline.ll b/test/CodeGen/AArch64/O3-pipeline.ll
index 03815481ef5cdb69d6fde41512dadf04cb727572..a331ac87f8f4829cb380d9a0b98f0f53833d206d 100644 (file)
--- a/test/CodeGen/AArch64/O3-pipeline.ll
+++ b/test/CodeGen/AArch64/O3-pipeline.ll
@@ -55,6 +55,7 @@
 ; CHECK-NEXT:       Interleaved Load Combine Pass
 ; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Interleaved Access Pass
+; CHECK-NEXT:       AArch64 Stack Tagging
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       CodeGen Prepare
 ; CHECK-NEXT:     Rewrite Symbols

diff --git a/test/CodeGen/AArch64/stack-tagging-dbg.ll b/test/CodeGen/AArch64/stack-tagging-dbg.ll
new file mode 100644 (file)
index 0000000..9ca4ff5
--- /dev/null
+++ b/test/CodeGen/AArch64/stack-tagging-dbg.ll
@@ -0,0 +1,37 @@
+; RUN: opt < %s -stack-tagging -S -o - | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64--linux-android"
+
+declare void @use32(i32*)
+declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone speculatable
+
+; Debug intrinsics use the new alloca directly, not through a GEP or a tagp.
+define void @DbgIntrinsics() sanitize_memtag {
+entry:
+  %x = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %x, metadata !6, metadata !DIExpression()), !dbg !10
+  store i32 42, i32* %x, align 4
+  call void @use32(i32* %x)
+  ret void
+}
+
+; CHECK-LABEL: define void @DbgIntrinsics(
+; CHECK:  [[X:%.*]] = alloca { i32, [12 x i8] }, align 16
+; CHECK:  call void @llvm.dbg.declare(metadata { i32, [12 x i8] }* [[X]],
+
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!8, !9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 9.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "stack-tagging.cc", directory: "/tmp")
+!2 = !{}
+!3 = distinct !DISubprogram(name: "DbgIntrinsics", linkageName: "DbgIntrinsics", scope: !1, file: !1, line: 3, type: !4, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!4 = !DISubroutineType(types: !5)
+!5 = !{null}
+!6 = !DILocalVariable(name: "x", scope: !3, file: !1, line: 4, type: !7)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = !{i32 2, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+!10 = !DILocation(line: 1, column: 2, scope: !3)

diff --git a/test/CodeGen/AArch64/stack-tagging.ll b/test/CodeGen/AArch64/stack-tagging.ll
new file mode 100644 (file)
index 0000000..244a0a1
--- /dev/null
+++ b/test/CodeGen/AArch64/stack-tagging.ll
@@ -0,0 +1,187 @@
+; RUN: opt < %s -stack-tagging -S -o - | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64--linux-android"
+
+declare void @use8(i8*)
+declare void @use32(i32*)
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
+
+define void @OneVar() sanitize_memtag {
+entry:
+  %x = alloca i32, align 4
+  call void @use32(i32* %x)
+  ret void
+}
+
+; CHECK-LABEL: define void @OneVar(
+; CHECK:  [[BASE:%.*]] = call i8* @llvm.aarch64.irg.sp(i64 0)
+; CHECK:  [[X:%.*]] = alloca { i32, [12 x i8] }, align 16
+; CHECK:  [[TX:%.*]] = call { i32, [12 x i8] }* @llvm.aarch64.tagp.{{.*}}({ i32, [12 x i8] }* [[X]], i8* [[BASE]], i64 0)
+; CHECK:  [[TX8:%.*]] = bitcast { i32, [12 x i8] }* [[TX]] to i8*
+; CHECK:  call void @llvm.aarch64.settag(i8* [[TX8]], i64 16)
+; CHECK:  [[GEP32:%.*]] = bitcast { i32, [12 x i8] }* [[TX]] to i32*
+; CHECK:  call void @use32(i32* [[GEP32]])
+; CHECK:  [[GEP8:%.*]] = bitcast { i32, [12 x i8] }* [[X]] to i8*
+; CHECK:  call void @llvm.aarch64.settag(i8* [[GEP8]], i64 16)
+; CHECK:  ret void
+
+
+define void @ManyVars() sanitize_memtag {
+entry:
+  %x1 = alloca i32, align 4
+  %x2 = alloca i8, align 4
+  %x3 = alloca i32, i32 11, align 4
+  call void @use32(i32* %x1)
+  call void @use8(i8* %x2)
+  call void @use32(i32* %x3)
+  ret void
+}
+
+; CHECK-LABEL: define void @ManyVars(
+; CHECK:  alloca { i32, [12 x i8] }, align 16
+; CHECK:  call { i32, [12 x i8] }* @llvm.aarch64.tagp.{{.*}}({ i32, [12 x i8] }* {{.*}}, i64 0)
+; CHECK:  call void @llvm.aarch64.settag(i8* {{.*}}, i64 16)
+; CHECK:  alloca { i8, [15 x i8] }, align 16
+; CHECK:  call { i8, [15 x i8] }* @llvm.aarch64.tagp.{{.*}}({ i8, [15 x i8] }* {{.*}}, i64 1)
+; CHECK:  call void @llvm.aarch64.settag(i8* {{.*}}, i64 16)
+; CHECK:  alloca { [11 x i32], [4 x i8] }, align 16
+; CHECK:  call { [11 x i32], [4 x i8] }* @llvm.aarch64.tagp.{{.*}}({ [11 x i32], [4 x i8] }* {{.*}}, i64 2)
+; CHECK:  call void @llvm.aarch64.settag(i8* {{.*}}, i64 48)
+
+; CHECK:  call void @use32(
+; CHECK:  call void @use8(
+; CHECK:  call void @use32(
+
+; CHECK:  call void @llvm.aarch64.settag(i8* {{.*}}, i64 16)
+; CHECK:  call void @llvm.aarch64.settag(i8* {{.*}}, i64 16)
+; CHECK:  call void @llvm.aarch64.settag(i8* {{.*}}, i64 48)
+; CHECK-NEXT:  ret void
+
+
+define void @Scope(i32 %b) sanitize_memtag {
+entry:
+  %x = alloca i32, align 4
+  %tobool = icmp eq i32 %b, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  %0 = bitcast i32* %x to i8*
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %0)
+  call void @use8(i8* %0) #3
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %0)
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+; CHECK-LABEL: define void @Scope(
+; CHECK:  br i1
+; CHECK:  call void @llvm.lifetime.start.p0i8(
+; CHECK:  call void @llvm.aarch64.settag(
+; CHECK:  call void @use8(
+; CHECK:  call void @llvm.aarch64.settag(
+; CHECK:  call void @llvm.lifetime.end.p0i8(
+; CHECK:  br label
+; CHECK:  ret void
+
+
+; Spooked by the multiple lifetime ranges, StackTagging remove all of them and sets tags on entry and exit.
+define void @BadScope(i32 %b) sanitize_memtag {
+entry:
+  %x = alloca i32, align 4
+  %tobool = icmp eq i32 %b, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  %0 = bitcast i32* %x to i8*
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %0)
+  call void @use8(i8* %0) #3
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %0)
+
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %0)
+  call void @use8(i8* %0) #3
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %0)
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+; CHECK-LABEL: define void @BadScope(
+; CHECK:       call void @llvm.aarch64.settag(i8* {{.*}}, i64 16)
+; CHECK:       br i1
+; CHECK:       call void @use8(i8*
+; CHECK-NEXT:  call void @use8(i8*
+; CHECK:       br label
+; CHECK:       call void @llvm.aarch64.settag(i8* {{.*}}, i64 16)
+; CHECK-NEXT:  ret void
+
+define void @DynamicAllocas(i32 %cnt) sanitize_memtag {
+entry:
+  %x = alloca i32, i32 %cnt, align 4
+  br label %l
+l:
+  %y = alloca i32, align 4
+  call void @use32(i32* %x)
+  call void @use32(i32* %y)
+  ret void
+}
+
+; CHECK-LABEL: define void @DynamicAllocas(
+; CHECK-NOT: @llvm.aarch64.irg.sp
+; CHECK:     %x = alloca i32, i32 %cnt, align 4
+; CHECK-NOT: @llvm.aarch64.irg.sp
+; CHECK:     alloca i32, align 4
+; CHECK-NOT: @llvm.aarch64.irg.sp
+; CHECK:     ret void
+
+; If we can't trace one of the lifetime markers to a single alloca, fall back
+; to poisoning all allocas at the beginning of the function.
+; Each alloca must be poisoned only once.
+define void @UnrecognizedLifetime(i8 %v) sanitize_memtag {
+entry:
+  %x = alloca i32, align 4
+  %y = alloca i32, align 4
+  %z = alloca i32, align 4
+  %cx = bitcast i32* %x to i8*
+  %cy = bitcast i32* %y to i8*
+  %cz = bitcast i32* %z to i8*
+  %tobool = icmp eq i8 %v, 0
+  %xy = select i1 %tobool, i32* %x, i32* %y
+  %cxcy = select i1 %tobool, i8* %cx, i8* %cy
+  br label %another_bb
+
+another_bb:
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %cz)
+  store i32 7, i32* %z
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %cz)
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %cz)
+  store i32 7, i32* %z
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %cz)
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %cxcy)
+  store i32 8, i32* %xy
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %cxcy)
+  ret void
+}
+
+; CHECK-LABEL: define void @UnrecognizedLifetime(
+; CHECK: call i8* @llvm.aarch64.irg.sp(i64 0)
+; CHECK: alloca { i32, [12 x i8] }, align 16
+; CHECK: call { i32, [12 x i8] }* @llvm.aarch64.tagp
+; CHECK: call void @llvm.aarch64.settag(
+; CHECK: alloca { i32, [12 x i8] }, align 16
+; CHECK: call { i32, [12 x i8] }* @llvm.aarch64.tagp
+; CHECK: call void @llvm.aarch64.settag(
+; CHECK: alloca { i32, [12 x i8] }, align 16
+; CHECK: call { i32, [12 x i8] }* @llvm.aarch64.tagp
+; CHECK: call void @llvm.aarch64.settag(
+; CHECK: store i32
+; CHECK: store i32
+; CHECK: store i32
+; CHECK: call void @llvm.aarch64.settag(
+; CHECK: call void @llvm.aarch64.settag(
+; CHECK: call void @llvm.aarch64.settag(
+; CHECK: ret void