[NFC][HWASan] Refactor hwasan pass

[leonardchan]

Summary

This moves some code for getting PC and SP into their own functions. Since SP is also retrieved in the prologue and getting the stack tag, we can cache the SP if we get it once in the prologue. This caching will really only be relevant in D128387 where StackBaseTag may not be set in the prologue if __hwasan_tls is not used.

[vitalybuka]

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

1111–1120

llvm mostly don't use {} for one liners
and we can avoid variables

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

public:
   Value *applyTagMask(IRBuilder<> &IRB, Value *OldTag);
   unsigned retagMask(unsigned AllocaNo);
 
   void emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord);
 
   void instrumentGlobal(GlobalVariable *GV, uint8_t Tag);
   void instrumentGlobals();
 
+  Value *getPC(IRBuilder<> &IRB);
+  Value *getSP(IRBuilder<> &IRB);
+
   void instrumentPersonalityFunctions();
 
 private:
   LLVMContext *C;
   Module &M;
   const StackSafetyGlobalInfo *SSI;
   Triple TargetTriple;
   FunctionCallee HWAsanMemmove, HWAsanMemcpy, HWAsanMemset;
private:
 
   FunctionCallee HwasanTagMemoryFunc;
   FunctionCallee HwasanGenerateTagFunc;
 
   Constant *ShadowGlobal;
 
   Value *ShadowBase = nullptr;
   Value *StackBaseTag = nullptr;
+  Value *CachedSP = nullptr;
   GlobalValue *ThreadPtrGlobal = nullptr;
 };
 
 } // end anonymous namespace
 
 PreservedAnalyses HWAddressSanitizerPass::run(Module &M,
                                               ModuleAnalysisManager &MAM) {
   const StackSafetyGlobalInfo *SSI = nullptr;
Value *HWAddressSanitizer::getNextTagWithCall(IRBuilder<> &IRB) {
   return IRB.CreateZExt(IRB.CreateCall(HwasanGenerateTagFunc), IntptrTy);
 }
 
 Value *HWAddressSanitizer::getStackBaseTag(IRBuilder<> &IRB) {
   if (ClGenerateTagsWithCalls)
     return getNextTagWithCall(IRB);
   if (StackBaseTag)
     return StackBaseTag;
-  // FIXME: use addressofreturnaddress (but implement it in aarch64 backend
-  // first).
-  Module *M = IRB.GetInsertBlock()->getParent()->getParent();
-  auto GetStackPointerFn = Intrinsic::getDeclaration(
-      M, Intrinsic::frameaddress,
-      IRB.getInt8PtrTy(M->getDataLayout().getAllocaAddrSpace()));
-  Value *StackPointer = IRB.CreateCall(
-      GetStackPointerFn, {Constant::getNullValue(IRB.getInt32Ty())});
-
   // 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 = IRB.CreatePointerCast(StackPointer, IntptrTy);
+  Value *StackPointerLong = getSP(IRB);
   Value *StackTag =
       applyTagMask(IRB, IRB.CreateXor(StackPointerLong,
                                       IRB.CreateLShr(StackPointerLong, 20)));
   StackTag->setName("hwasan.stack.base.tag");
   return StackTag;
 }
 
 Value *HWAddressSanitizer::getAllocaTag(IRBuilder<> &IRB, Value *StackTag,
if (TargetTriple.isAArch64() && TargetTriple.isAndroid()) {
     return SlotPtr;
   }
   if (ThreadPtrGlobal)
     return ThreadPtrGlobal;
 
   return nullptr;
 }
 
+Value *HWAddressSanitizer::getPC(IRBuilder<> &IRB) {
+  if (TargetTriple.getArch() == Triple::aarch64)
+    return readRegister(IRB, "pc");
+  else
+    return IRB.CreatePtrToInt(IRB.GetInsertBlock()->getParent(), IntptrTy);
+}
+
+Value *HWAddressSanitizer::getSP(IRBuilder<> &IRB) {
+  if (!CachedSP) {
+    // FIXME: use addressofreturnaddress (but implement it in aarch64 backend
+    // first).
+    Function *F = IRB.GetInsertBlock()->getParent();
+    Module *M = F->getParent();
+    auto GetStackPointerFn = Intrinsic::getDeclaration(
+        M, Intrinsic::frameaddress,
+        IRB.getInt8PtrTy(M->getDataLayout().getAllocaAddrSpace()));
+    CachedSP = IRB.CreatePtrToInt(
+        IRB.CreateCall(GetStackPointerFn,
+                       {Constant::getNullValue(IRB.getInt32Ty())}),
+        IntptrTy);
+  }
+  return CachedSP;
+}
+
 void HWAddressSanitizer::emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord) {
   if (!Mapping.InTls)
     ShadowBase = getShadowNonTls(IRB);
   else if (!WithFrameRecord && TargetTriple.isAndroid())
     ShadowBase = getDynamicShadowIfunc(IRB);
 
   if (!WithFrameRecord && ShadowBase)
     return;
 
   Value *SlotPtr = getHwasanThreadSlotPtr(IRB, IntptrTy);
   assert(SlotPtr);
 
   Value *ThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
   // Extract the address field from ThreadLong. Unnecessary on AArch64 with TBI.
   Value *ThreadLongMaybeUntagged =
       TargetTriple.isAArch64() ? ThreadLong : untagPointer(IRB, ThreadLong);
 
   if (WithFrameRecord) {
-    Function *F = IRB.GetInsertBlock()->getParent();
     StackBaseTag = IRB.CreateAShr(ThreadLong, 3);
 
     // Prepare ring buffer data.
-    Value *PC;
-    if (TargetTriple.getArch() == Triple::aarch64)
-      PC = readRegister(IRB, "pc");
-    else
-      PC = IRB.CreatePtrToInt(F, IntptrTy);
-    Module *M = F->getParent();
-    auto GetStackPointerFn = Intrinsic::getDeclaration(
-        M, Intrinsic::frameaddress,
-        IRB.getInt8PtrTy(M->getDataLayout().getAllocaAddrSpace()));
-    Value *SP = IRB.CreatePtrToInt(
-        IRB.CreateCall(GetStackPointerFn,
-                       {Constant::getNullValue(IRB.getInt32Ty())}),
-        IntptrTy);
+    Value *PC = getPC(IRB);
+    Value *SP = getSP(IRB);
+
     // Mix SP and PC.
     // Assumptions:
     // PC is 0x0000PPPPPPPPPPPP  (48 bits are meaningful, others are zero)
     // SP is 0xsssssssssssSSSS0  (4 lower bits are zero)
     // We only really need ~20 lower non-zero bits (SSSS), so we mix like this:
     //       0xSSSSPPPPPPPPPPPP
     SP = IRB.CreateShl(SP, 44);
 
bool HWAddressSanitizer::sanitizeFunction(Function &F,
 
   if (ClInstrumentMemIntrinsics && !IntrinToInstrument.empty()) {
     for (auto Inst : IntrinToInstrument)
       instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
   }
 
   ShadowBase = nullptr;
   StackBaseTag = nullptr;
+  CachedSP = nullptr;
 
   return true;
 }
 
 void HWAddressSanitizer::instrumentGlobal(GlobalVariable *GV, uint8_t Tag) {
   assert(!UsePageAliases);
   Constant *Initializer = GV->getInitializer();
   uint64_t SizeInBytes =