[MC/DC] Rework tvbitmap.update (llvm#96040) to get rid of the inlined function

Per the discussion in llvm#102542, it is safe to insert BBs under
`lowerIntrinsics()` since llvm#69535 has made tolerant of modifying BBs.

So, I can get rid of using the inlined function `rmw_or`.

Author: chapuni

llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp

@@ -267,10 +267,6 @@ class InstrLowerer final {
   GlobalVariable *NamesVar = nullptr;
   size_t NamesSize = 0;
 
-  /// The instance of [[alwaysinline]] rmw_or(ptr, i8).
-  /// This is name-insensitive.
-  Function *RMWOrFunc = nullptr;
-
   // vector of counter load/store pairs to be register promoted.
   std::vector<LoadStorePair> PromotionCandidates;
 
@@ -337,14 +333,6 @@ class InstrLowerer final {
                                        StringRef Name,
                                        GlobalValue::LinkageTypes Linkage);
 
-  /// Create [[alwaysinline]] rmw_or(ptr, i8).
-  /// This doesn't update `RMWOrFunc`.
-  Function *createRMWOrFunc();
-
-  /// Get the call to `rmw_or`.
-  /// Create the instance if it is unknown.
-  CallInst *getRMWOrCall(Value *Addr, Value *Val);
-
   /// Compute the address of the test vector bitmap that this profiling
   /// instruction acts on.
   Value *getBitmapAddress(InstrProfMCDCTVBitmapUpdate *I);
@@ -1137,68 +1125,6 @@ Value *InstrLowerer::getCounterAddress(InstrProfCntrInstBase *I) {
   return Builder.CreateIntToPtr(Add, Addr->getType());
 }
 
-/// Create `void [[alwaysinline]] rmw_or(uint8_t *ArgAddr, uint8_t ArgVal)`
-/// "Basic" sequence is `*ArgAddr |= ArgVal`
-Function *InstrLowerer::createRMWOrFunc() {
-  auto &Ctx = M.getContext();
-  auto *Int8Ty = Type::getInt8Ty(Ctx);
-  Function *Fn = Function::Create(
-      FunctionType::get(Type::getVoidTy(Ctx),
-                        {PointerType::getUnqual(Ctx), Int8Ty}, false),
-      Function::LinkageTypes::PrivateLinkage, "rmw_or", M);
-  Fn->addFnAttr(Attribute::AlwaysInline);
-  auto *ArgAddr = Fn->getArg(0);
-  auto *ArgVal = Fn->getArg(1);
-  IRBuilder<> Builder(BasicBlock::Create(Ctx, "", Fn));
-
-  // Load profile bitmap byte.
-  //  %mcdc.bits = load i8, ptr %4, align 1
-  auto *Bitmap = Builder.CreateLoad(Int8Ty, ArgAddr, "mcdc.bits");
-
-  if (Options.Atomic || AtomicCounterUpdateAll) {
-    // If ((Bitmap & Val) != Val), then execute atomic (Bitmap |= Val).
-    // Note, just-loaded Bitmap might not be up-to-date. Use it just for
-    // early testing.
-    auto *Masked = Builder.CreateAnd(Bitmap, ArgVal);
-    auto *ShouldStore = Builder.CreateICmpNE(Masked, ArgVal);
-    auto *ThenTerm = BasicBlock::Create(Ctx, "", Fn);
-    auto *ElseTerm = BasicBlock::Create(Ctx, "", Fn);
-    // Assume updating will be rare.
-    auto *Unlikely = MDBuilder(Ctx).createUnlikelyBranchWeights();
-    Builder.CreateCondBr(ShouldStore, ThenTerm, ElseTerm, Unlikely);
-
-    IRBuilder<> ThenBuilder(ThenTerm);
-    ThenBuilder.CreateAtomicRMW(AtomicRMWInst::Or, ArgAddr, ArgVal,
-                                MaybeAlign(), AtomicOrdering::Monotonic);
-    ThenBuilder.CreateRetVoid();
-
-    IRBuilder<> ElseBuilder(ElseTerm);
-    ElseBuilder.CreateRetVoid();
-
-    return Fn;
-  }
-
-  // Perform logical OR of profile bitmap byte and shifted bit offset.
-  //  %8 = or i8 %mcdc.bits, %7
-  auto *Result = Builder.CreateOr(Bitmap, ArgVal);
-
-  // Store the updated profile bitmap byte.
-  //  store i8 %8, ptr %3, align 1
-  Builder.CreateStore(Result, ArgAddr);
-
-  // Terminator
-  Builder.CreateRetVoid();
-
-  return Fn;
-}
-
-CallInst *InstrLowerer::getRMWOrCall(Value *Addr, Value *Val) {
-  if (!RMWOrFunc)
-    RMWOrFunc = createRMWOrFunc();
-
-  return CallInst::Create(RMWOrFunc, {Addr, Val});
-}
-
 Value *InstrLowerer::getBitmapAddress(InstrProfMCDCTVBitmapUpdate *I) {
   auto *Bitmaps = getOrCreateRegionBitmaps(I);
   if (!isRuntimeCounterRelocationEnabled())
@@ -1291,9 +1217,10 @@ void InstrLowerer::lowerCoverageData(GlobalVariable *CoverageNamesVar) {
 
 void InstrLowerer::lowerMCDCTestVectorBitmapUpdate(
     InstrProfMCDCTVBitmapUpdate *Update) {
+  auto &Ctx = M.getContext();
   IRBuilder<> Builder(Update);
-  auto *Int8Ty = Type::getInt8Ty(M.getContext());
-  auto *Int32Ty = Type::getInt32Ty(M.getContext());
+  auto *Int8Ty = Type::getInt8Ty(Ctx);
+  auto *Int32Ty = Type::getInt32Ty(Ctx);
   auto *MCDCCondBitmapAddr = Update->getMCDCCondBitmapAddr();
   auto *BitmapAddr = getBitmapAddress(Update);
 
@@ -1321,7 +1248,36 @@ void InstrLowerer::lowerMCDCTestVectorBitmapUpdate(
   //  %7 = shl i8 1, %6
   auto *ShiftedVal = Builder.CreateShl(Builder.getInt8(0x1), BitToSet);
 
-  Builder.Insert(getRMWOrCall(BitmapByteAddr, ShiftedVal));
+  // Load profile bitmap byte.
+  //  %mcdc.bits = load i8, ptr %4, align 1
+  auto *Bitmap = Builder.CreateLoad(Int8Ty, BitmapByteAddr, "mcdc.bits");
+
+  if (Options.Atomic || AtomicCounterUpdateAll) {
+    // If ((Bitmap & Val) != Val), then execute atomic (Bitmap |= Val).
+    // Note, just-loaded Bitmap might not be up-to-date. Use it just for
+    // early testing.
+    auto *Masked = Builder.CreateAnd(Bitmap, ShiftedVal);
+    auto *ShouldStore = Builder.CreateICmpNE(Masked, ShiftedVal);
+
+    // Assume updating will be rare.
+    auto *Unlikely = MDBuilder(Ctx).createUnlikelyBranchWeights();
+    Instruction *ThenBranch =
+        SplitBlockAndInsertIfThen(ShouldStore, Update, false, Unlikely);
+
+    // Execute if (unlikely(ShouldStore)).
+    Builder.SetInsertPoint(ThenBranch);
+    Builder.CreateAtomicRMW(AtomicRMWInst::Or, BitmapByteAddr, ShiftedVal,
+                            MaybeAlign(), AtomicOrdering::Monotonic);
+  } else {
+    // Perform logical OR of profile bitmap byte and shifted bit offset.
+    //  %8 = or i8 %mcdc.bits, %7
+    auto *Result = Builder.CreateOr(Bitmap, ShiftedVal);
+
+    // Store the updated profile bitmap byte.
+    //  store i8 %8, ptr %3, align 1
+    Builder.CreateStore(Result, BitmapByteAddr);
+  }
+
   Update->eraseFromParent();
 }
 

llvm/test/Instrumentation/InstrProfiling/mcdc.ll

@@ -36,25 +36,21 @@ entry:
   ; CHECK-NEXT: %[[LAB8:[0-9]+]] = and i32 %[[TEMP]], 7
   ; CHECK-NEXT: %[[LAB9:[0-9]+]] = trunc i32 %[[LAB8]] to i8
   ; CHECK-NEXT: %[[LAB10:[0-9]+]] = shl i8 1, %[[LAB9]]
-  ; CHECK-NEXT: call void @[[RMW_OR:.+]](ptr %[[LAB7]], i8 %[[LAB10]])
+  ; CHECK-NEXT: %[[BITS:.+]] = load i8, ptr %[[LAB7]], align 1
+  ; ATOMIC-NEXT: %[[MASKED:.+]] = and i8 %[[BITS]], %[[LAB10]]
+  ; ATOMIC-NEXT: %[[SHOULDWRITE:.+]] = icmp ne i8 %[[MASKED]], %[[LAB10]]
+  ; ATOMIC-NEXT: br i1 %[[SHOULDWRITE]], label %[[WRITE:.+]], label %[[SKIP:.+]], !prof ![[MDPROF:[0-9]+]]
+  ; ATOMIC: [[WRITE]]:
+  ; BASIC-NEXT: %[[LAB11:[0-9]+]] = or i8 %[[BITS]], %[[LAB10]]
+  ; RELOC-NEXT: %[[LAB11:[0-9]+]] = or i8 %[[BITS]], %[[LAB10]]
+  ; BASIC-NEXT: store i8 %[[LAB11]], ptr %[[LAB7]], align 1
+  ; RELOC-NEXT: store i8 %[[LAB11]], ptr %[[LAB7]], align 1
+  ; ATOMIC-NEXT: %{{.+}} = atomicrmw or ptr %[[LAB7]], i8 %[[LAB10]] monotonic, align 1
+  ; ATOMIC: [[SKIP]]:
   ret void
+  ; CHECK-NEXT: ret void
 }
 
-; CHECK: define private void @[[RMW_OR]](ptr %[[ARGPTR:.+]], i8 %[[ARGVAL:.+]])
-; CHECK:      %[[BITS:.+]] = load i8, ptr %[[ARGPTR]], align 1
-; BASIC-NEXT: %[[LAB11:[0-9]+]] = or i8 %[[BITS]], %[[ARGVAL]]
-; RELOC-NEXT: %[[LAB11:[0-9]+]] = or i8 %[[BITS]], %[[ARGVAL]]
-; BASIC-NEXT: store i8 %[[LAB11]], ptr %[[ARGPTR]], align 1
-; RELOC-NEXT: store i8 %[[LAB11]], ptr %[[ARGPTR]], align 1
-; ATOMIC-NEXT: %[[MASKED:.+]] = and i8 %[[BITS]], %[[ARGVAL]]
-; ATOMIC-NEXT: %[[SHOULDWRITE:.+]] = icmp ne i8 %[[MASKED]], %[[ARGVAL]]
-; ATOMIC-NEXT: br i1 %[[SHOULDWRITE]], label %[[WRITE:.+]], label %[[SKIP:.+]], !prof ![[MDPROF:[0-9]+]]
-; ATOMIC: [[WRITE]]:
-; ATOMIC-NEXT: %{{.+}} = atomicrmw or ptr %[[ARGPTR]], i8 %[[ARGVAL]] monotonic, align 1
-; ATOMIC-NEXT: ret void
-; ATOMIC: [[SKIP]]:
-; CHECK-NEXT: ret void
-
 ; ATOMIC: ![[MDPROF]] = !{!"branch_weights", i32 1, i32 1048575}
 
 declare void @llvm.instrprof.cover(ptr, i64, i32, i32)