[NFC][HWASAN] Move getUARTag into the Entry

[kstoimenov]

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

1049

Should we make this into an assert?

[eugenis]

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

1049

nullptr is fine because we do not need the base tag when ClGenerateTagsWithCalls.

We could turn it into Optional<> but I do not see the point.

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

public:
   bool instrumentMemAccess(InterestingMemoryOperand &O);
   bool ignoreAccess(Instruction *Inst, Value *Ptr);
   void getInterestingMemoryOperands(
       Instruction *I, SmallVectorImpl<InterestingMemoryOperand> &Interesting);
 
   void tagAlloca(IRBuilder<> &IRB, AllocaInst *AI, Value *Tag, size_t Size);
   Value *tagPointer(IRBuilder<> &IRB, Type *Ty, Value *PtrLong, Value *Tag);
   Value *untagPointer(IRBuilder<> &IRB, Value *PtrLong);
-  bool instrumentStack(memtag::StackInfo &Info, Value *StackTag,
+  bool instrumentStack(memtag::StackInfo &Info, Value *StackTag, Value *UARTag,
                        const DominatorTree &DT, const PostDominatorTree &PDT,
                        const LoopInfo &LI);
   Value *readRegister(IRBuilder<> &IRB, StringRef Name);
   bool instrumentLandingPads(SmallVectorImpl<Instruction *> &RetVec);
   Value *getNextTagWithCall(IRBuilder<> &IRB);
   Value *getStackBaseTag(IRBuilder<> &IRB);
   Value *getAllocaTag(IRBuilder<> &IRB, Value *StackTag, AllocaInst *AI,
                       unsigned AllocaNo);
Value *HWAddressSanitizer::applyTagMask(IRBuilder<> &IRB, Value *OldTag) {
   return IRB.CreateAnd(OldTag, ConstantInt::get(IntptrTy, TagMaskByte));
 }
 
 Value *HWAddressSanitizer::getNextTagWithCall(IRBuilder<> &IRB) {
   return IRB.CreateZExt(IRB.CreateCall(HwasanGenerateTagFunc), IntptrTy);
 }
 
 Value *HWAddressSanitizer::getStackBaseTag(IRBuilder<> &IRB) {
   if (ClGenerateTagsWithCalls)
-    return getNextTagWithCall(IRB);
+    return nullptr;
   if (StackBaseTag)
     return StackBaseTag;
   // Extract some entropy from the stack pointer for the tags.
   // Take bits 20..28 (ASLR entropy) and xor with bits 0..8 (these differ
   // between functions).
   Value *StackPointerLong = getSP(IRB);
   Value *StackTag =
       applyTagMask(IRB, IRB.CreateXor(StackPointerLong,

 }
 
 static bool isLifetimeIntrinsic(Value *V) {
   auto *II = dyn_cast<IntrinsicInst>(V);
   return II && II->isLifetimeStartOrEnd();
 }
 
 bool HWAddressSanitizer::instrumentStack(memtag::StackInfo &SInfo,
-                                         Value *StackTag,
+                                         Value *StackTag, Value *UARTag,
                                          const DominatorTree &DT,
                                          const PostDominatorTree &PDT,
                                          const LoopInfo &LI) {
   // Ideally, we want to calculate tagged stack base pointer, and rewrite all
   // alloca addresses using that. Unfortunately, offsets are not known yet
   // (unless we use ASan-style mega-alloca). Instead we keep the base tag in a
   // temp, shift-OR it into each alloca address and xor with the retag mask.
   // This generates one extra instruction per alloca use.
for (auto *DDI : Info.DbgVariableIntrinsics) {
       for (size_t LocNo = 0; LocNo < DDI->getNumVariableLocationOps(); ++LocNo)
         if (DDI->getVariableLocationOp(LocNo) == AI)
           DDI->setExpression(DIExpression::appendOpsToArg(DDI->getExpression(),
                                                           NewOps, LocNo));
     }
 
     auto TagEnd = [&](Instruction *Node) {
       IRB.SetInsertPoint(Node);
-      Value *UARTag = getUARTag(IRB);
       // When untagging, use the `AlignedSize` because we need to set the tags
       // for the entire alloca to zero. If we used `Size` here, we would
       // keep the last granule tagged, and store zero in the last byte of the
       // last granule, due to how short granules are implemented.
       tagAlloca(IRB, AI, UARTag, AlignedSize);
     };
     // Calls to functions that may return twice (e.g. setjmp) confuse the
     // postdominator analysis, and will leave us to keep memory tagged after
emitPrologue(EntryIRB,
                /*WithFrameRecord*/ ClRecordStackHistory != none &&
                    Mapping.WithFrameRecord &&
                    !SInfo.AllocasToInstrument.empty());
 
   if (!SInfo.AllocasToInstrument.empty()) {
     const DominatorTree &DT = FAM.getResult<DominatorTreeAnalysis>(F);
     const PostDominatorTree &PDT = FAM.getResult<PostDominatorTreeAnalysis>(F);
     const LoopInfo &LI = FAM.getResult<LoopAnalysis>(F);
-    Value *StackTag =
-        ClGenerateTagsWithCalls ? nullptr : getStackBaseTag(EntryIRB);
-    instrumentStack(SInfo, StackTag, DT, PDT, LI);
+    Value *StackTag = getStackBaseTag(EntryIRB);
+    Value *UARTag = getUARTag(EntryIRB);
+    instrumentStack(SInfo, StackTag, UARTag, DT, PDT, LI);
   }
 
   // If we split the entry block, move any allocas that were originally in the
   // entry block back into the entry block so that they aren't treated as
   // dynamic allocas.
   if (EntryIRB.GetInsertBlock() != &F.getEntryBlock()) {
     InsertPt = &*F.getEntryBlock().begin();
     for (Instruction &I :