[TBAA] Drop support for "old style" scalar TBAA tags

Summary:
We've had support for auto upgrading old style scalar TBAA access
metadata tags into the "new" struct path aware TBAA metadata for 3 years
now.  The only way to actually generate old style TBAA was explicitly
through the IRBuilder API.  I think this is a good time for dropping
support for old style scalar TBAA.

I'm not removing support for textual or bitcode upgrade -- if you have
IR with the old style scalar TBAA tags that go through the AsmParser orf
the bitcode parser before LLVM sees them, they will keep working as
usual.

Note:

  %val = load i32, i32* %ptr, !tbaa !N
  !N = < scalar tbaa node >

is equivalent to

  %val = load i32, i32* %ptr, !tbaa !M
  !N = < scalar tbaa node >
  !M = !{!N, !N, 0}

Reviewers: manmanren, chandlerc, sunfish

Subscribers: mcrosier, llvm-commits, mgorny

Differential Revision: https://reviews.llvm.org/D26229

llvm-svn: 286291

llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp

@@ -417,15 +417,14 @@ MDNode *MDNode::getMostGenericTBAA(MDNode *A, MDNode *B) {
     return A;
 
   // For struct-path aware TBAA, we use the access type of the tag.
-  bool StructPath = isStructPathTBAA(A) && isStructPathTBAA(B);
+  assert(isStructPathTBAA(A) && isStructPathTBAA(B) &&
-  if (StructPath) {
+         "Auto upgrade should have taken care of this!");
-    A = cast_or_null<MDNode>(MutableTBAAStructTagNode(A).getAccessType());
+  A = cast_or_null<MDNode>(MutableTBAAStructTagNode(A).getAccessType());
-    if (!A)
+  if (!A)
-      return nullptr;
+    return nullptr;
-    B = cast_or_null<MDNode>(MutableTBAAStructTagNode(B).getAccessType());
+  B = cast_or_null<MDNode>(MutableTBAAStructTagNode(B).getAccessType());
-    if (!B)
+  if (!B)
-      return nullptr;
+    return nullptr;
-  }
 
   SmallSetVector<MDNode *, 4> PathA;
   MutableTBAANode TA(A);
@@ -457,8 +456,6 @@ MDNode *MDNode::getMostGenericTBAA(MDNode *A, MDNode *B) {
     --IA;
     --IB;
   }
-  if (!StructPath)
-    return Ret;
 
   if (!Ret)
     return nullptr;
@@ -492,52 +489,8 @@ void Instruction::getAAMetadata(AAMDNodes &N, bool Merge) const {
 /// Aliases - Test whether the type represented by A may alias the
 /// type represented by B.
 bool TypeBasedAAResult::Aliases(const MDNode *A, const MDNode *B) const {
-  // Make sure that both MDNodes are struct-path aware.
+  // Verify that both input nodes are struct-path aware.  Auto-upgrade should
-  if (isStructPathTBAA(A) && isStructPathTBAA(B))
+  // have taken care of this.
-    return PathAliases(A, B);
-
-  // Keep track of the root node for A and B.
-  TBAANode RootA, RootB;
-
-  // Climb the tree from A to see if we reach B.
-  for (TBAANode T(A);;) {
-    if (T.getNode() == B)
-      // B is an ancestor of A.
-      return true;
-
-    RootA = T;
-    T = T.getParent();
-    if (!T.getNode())
-      break;
-  }
-
-  // Climb the tree from B to see if we reach A.
-  for (TBAANode T(B);;) {
-    if (T.getNode() == A)
-      // A is an ancestor of B.
-      return true;
-
-    RootB = T;
-    T = T.getParent();
-    if (!T.getNode())
-      break;
-  }
-
-  // Neither node is an ancestor of the other.
-
-  // If they have different roots, they're part of different potentially
-  // unrelated type systems, so we must be conservative.
-  if (RootA.getNode() != RootB.getNode())
-    return true;
-
-  // If they have the same root, then we've proved there's no alias.
-  return false;
-}
-
-/// Test whether the struct-path tag represented by A may alias the
-/// struct-path tag represented by B.
-bool TypeBasedAAResult::PathAliases(const MDNode *A, const MDNode *B) const {
-  // Verify that both input nodes are struct-path aware.
   assert(isStructPathTBAA(A) && "MDNode A is not struct-path aware.");
   assert(isStructPathTBAA(B) && "MDNode B is not struct-path aware.");
 

llvm/lib/IR/Verifier.cpp

@@ -391,6 +391,7 @@ private:
   void visitBasicBlock(BasicBlock &BB);
   void visitRangeMetadata(Instruction& I, MDNode* Range, Type* Ty);
   void visitDereferenceableMetadata(Instruction& I, MDNode* MD);
+  void visitTBAAMetadata(Instruction &I, MDNode *MD);
 
   template <class Ty> bool isValidMetadataArray(const MDTuple &N);
 #define HANDLE_SPECIALIZED_MDNODE_LEAF(CLASS) void visit##CLASS(const CLASS &N);
@@ -3658,6 +3659,15 @@ void Verifier::visitDereferenceableMetadata(Instruction& I, MDNode* MD) {
          "dereferenceable_or_null metadata value must be an i64!", &I);
 }
 
+void Verifier::visitTBAAMetadata(Instruction &I, MDNode *MD) {
+  bool IsStructPathTBAA =
+      isa<MDNode>(MD->getOperand(0)) && MD->getNumOperands() >= 3;
+
+  Assert(IsStructPathTBAA,
+         "Old-style TBAA is no longer allowed, use struct-path TBAA instead",
+         &I);
+}
+
 /// verifyInstruction - Verify that an instruction is well formed.
 ///
 void Verifier::visitInstruction(Instruction &I) {
@@ -3793,6 +3803,9 @@ void Verifier::visitInstruction(Instruction &I) {
   if (MDNode *MD = I.getMetadata(LLVMContext::MD_dereferenceable_or_null))
     visitDereferenceableMetadata(I, MD);
 
+  if (MDNode *MD = I.getMetadata(LLVMContext::MD_tbaa))
+    visitTBAAMetadata(I, MD);
+
   if (MDNode *AlignMD = I.getMetadata(LLVMContext::MD_align)) {
     Assert(I.getType()->isPointerTy(), "align applies only to pointer types",
            &I);

llvm/unittests/Analysis/CMakeLists.txt

@@ -14,7 +14,7 @@ add_llvm_unittest(AnalysisTests
   LazyCallGraphTest.cpp
   LoopPassManagerTest.cpp
   ScalarEvolutionTest.cpp
-  MixedTBAATest.cpp
+  TBAATest.cpp
   ValueTrackingTest.cpp
   UnrollAnalyzer.cpp
   )

llvm/unittests/Analysis/MixedTBAATest.cpp

@@ -1,79 +0,0 @@
-//===--- MixedTBAATest.cpp - Mixed TBAA unit tests ------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Analysis/TypeBasedAliasAnalysis.h"
-#include "llvm/Analysis/AliasAnalysisEvaluator.h"
-#include "llvm/Analysis/Passes.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/MDBuilder.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/LegacyPassManager.h"
-#include "llvm/Support/CommandLine.h"
-#include "gtest/gtest.h"
-
-namespace llvm {
-namespace {
-
-class MixedTBAATest : public testing::Test {
-protected:
-  MixedTBAATest() : M("MixedTBAATest", C), MD(C) {}
-
-  LLVMContext C;
-  Module M;
-  MDBuilder MD;
-  legacy::PassManager PM;
-};
-
-TEST_F(MixedTBAATest, MixedTBAA) {
-  // Setup function.
-  FunctionType *FTy = FunctionType::get(Type::getVoidTy(C),
-                                        std::vector<Type *>(), false);
-  auto *F = cast<Function>(M.getOrInsertFunction("f", FTy));
-  auto *BB = BasicBlock::Create(C, "entry", F);
-  auto IntType = Type::getInt32Ty(C);
-  auto PtrType = Type::getInt32PtrTy(C);
-  auto *Value  = ConstantInt::get(IntType, 42);
-  auto *Addr = ConstantPointerNull::get(PtrType);
-
-  auto *Store1 = new StoreInst(Value, Addr, BB);
-  auto *Store2 = new StoreInst(Value, Addr, BB);
-  ReturnInst::Create(C, nullptr, BB);
-
-  // New TBAA metadata
-  {
-    auto RootMD = MD.createTBAARoot("Simple C/C++ TBAA");
-    auto MD1 = MD.createTBAAScalarTypeNode("omnipotent char", RootMD);
-    auto MD2 = MD.createTBAAScalarTypeNode("int", MD1);
-    auto MD3 = MD.createTBAAStructTagNode(MD2, MD2, 0);
-    Store2->setMetadata(LLVMContext::MD_tbaa, MD3);
-  }
-
-  // Old TBAA metadata
-  {
-    auto RootMD = MD.createTBAARoot("Simple C/C++ TBAA");
-    auto MD1 = MD.createTBAANode("omnipotent char", RootMD);
-    auto MD2 = MD.createTBAANode("int", MD1);
-    Store1->setMetadata(LLVMContext::MD_tbaa, MD2);
-  }
-
-  // Run the TBAA eval pass on a mixture of path-aware and non-path-aware TBAA.
-  // The order of the metadata (path-aware vs non-path-aware) is important,
-  // because the AA eval pass only runs one test per store-pair.
-  const char* args[] = { "MixedTBAATest", "-evaluate-aa-metadata" };
-  cl::ParseCommandLineOptions(sizeof(args) / sizeof(const char*), args);
-  PM.add(createTypeBasedAAWrapperPass());
-  PM.add(createAAEvalPass());
-  PM.run(M);
-}
-
-} // end anonymous namspace
-} // end llvm namespace
-

llvm/unittests/Analysis/TBAATest.cpp

@@ -0,0 +1,63 @@
+//===--- TBAATest.cpp - Mixed TBAA unit tests -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/AliasAnalysisEvaluator.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/Support/CommandLine.h"
+#include "gtest/gtest.h"
+
+namespace llvm {
+namespace {
+
+class OldTBAATest : public testing::Test {
+protected:
+  OldTBAATest() : M("MixedTBAATest", C), MD(C) {}
+
+  LLVMContext C;
+  Module M;
+  MDBuilder MD;
+};
+
+TEST_F(OldTBAATest, checkVerifierBehavior) {
+  // C++ unit test case to avoid going through the auto upgrade logic.
+
+  FunctionType *FTy = FunctionType::get(Type::getVoidTy(C), {});
+  auto *F = cast<Function>(M.getOrInsertFunction("f", FTy));
+  auto *BB = BasicBlock::Create(C, "entry", F);
+  auto *IntType = Type::getInt32Ty(C);
+  auto *PtrType = Type::getInt32PtrTy(C);
+  auto *SI = new StoreInst(ConstantInt::get(IntType, 42),
+                           ConstantPointerNull::get(PtrType), BB);
+  ReturnInst::Create(C, nullptr, BB);
+
+  auto *RootMD = MD.createTBAARoot("Simple C/C++ TBAA");
+  auto *MD1 = MD.createTBAANode("omnipotent char", RootMD);
+  auto *MD2 = MD.createTBAANode("int", MD1);
+  SI->setMetadata(LLVMContext::MD_tbaa, MD2);
+
+  SmallVector<char, 0> ErrorMsg;
+  raw_svector_ostream Outs(ErrorMsg);
+
+  StringRef ExpectedFailureMsg(
+      "Old-style TBAA is no longer allowed, use struct-path TBAA instead");
+
+  EXPECT_TRUE(verifyFunction(*F, &Outs));
+  EXPECT_TRUE(StringRef(ErrorMsg.begin(), ErrorMsg.size())
+                  .startswith(ExpectedFailureMsg));
+}
+
+} // end anonymous namspace
+} // end llvm namespace