Reapply "Verifier: Check for incompatible bit piece expressions"

This reverts commit r234717, reapplying r234698 (in spirit).

As described in r234717, the original `Verifier` check had a
use-after-free.  Instead of storing pointers to "interesting" debug info
intrinsics whose bit piece expressions should be verified once we have
typerefs, do a second traversal.  I've added a testcase to catch the
`llc` crasher.

Original commit message:

    Verifier: Check for incompatible bit piece expressions

    Convert an assertion into a `Verifier` check.  Bit piece expressions
    must fit inside the variable, and mustn't be the entire variable.
    Catching this in the verifier will help us find bugs sooner, and makes
    `DIVariable::getSizeInBits()` dead code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234776 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/DebugInfo.h

@@ -735,9 +735,6 @@ public:
   /// \brief Check if this is an inlined function argument.
   bool isInlinedFnArgument(const Function *CurFn);
 
-  /// \brief Return the size reported by the variable's type.
-  unsigned getSizeInBits(const DITypeIdentifierMap &Map);
-
   void printExtendedName(raw_ostream &OS) const;
 };
 

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1536,14 +1536,6 @@ void DebugLocEntry::finalize(const AsmPrinter &AP,
       }
       Offset += PieceSize;
 
-#ifndef NDEBUG
-      DIVariable Var = Piece.getVariable();
-      unsigned VarSize = Var.getSizeInBits(TypeIdentifierMap);
-      assert(PieceSize+PieceOffset <= VarSize
-             && "piece is larger than or outside of variable");
-      assert(PieceSize != VarSize
-             && "piece covers entire variable");
-#endif
       emitDebugLocValue(AP, TypeIdentifierMap, Streamer, Piece, PieceOffset);
     }
   } else {

lib/IR/DebugInfo.cpp

@@ -33,19 +33,6 @@
 using namespace llvm;
 using namespace llvm::dwarf;
 
-/// \brief Return the size reported by the variable's type.
-unsigned DIVariable::getSizeInBits(const DITypeIdentifierMap &Map) {
-  DIType Ty = getType().resolve(Map);
-  // Follow derived types until we reach a type that
-  // reports back a size.
-  while (isa<MDDerivedType>(Ty) && !Ty.getSizeInBits()) {
-    DIDerivedType DT = cast<MDDerivedType>(Ty);
-    Ty = DT.getTypeDerivedFrom().resolve(Map);
-  }
-  assert(Ty.getSizeInBits() && "type with size 0");
-  return Ty.getSizeInBits();
-}
-
 //===----------------------------------------------------------------------===//
 // Simple Descriptor Constructors and other Methods
 //===----------------------------------------------------------------------===//

lib/IR/Verifier.cpp

@@ -178,8 +178,8 @@ class Verifier : public InstVisitor<Verifier>, VerifierSupport {
   /// \brief Keep track of the metadata nodes that have been checked already.
   SmallPtrSet<const Metadata *, 32> MDNodes;
 
-  /// \brief Track string-based type references.
-  SmallDenseMap<const MDString *, const MDNode *, 32> TypeRefs;
+  /// \brief Track unresolved string-based type references.
+  SmallDenseMap<const MDString *, const MDNode *, 32> UnresolvedTypeRefs;
 
   /// \brief The personality function referenced by the LandingPadInsts.
   /// All LandingPadInsts within the same function must use the same
@@ -407,6 +407,9 @@ private:
 
   // Module-level debug info verification...
   void verifyTypeRefs();
+  template <class MapTy>
+  void verifyBitPieceExpression(const DbgInfoIntrinsic &I,
+                                const MapTy &TypeRefs);
   void visitUnresolvedTypeRef(const MDString *S, const MDNode *N);
 };
 } // End anonymous namespace
@@ -702,7 +705,7 @@ bool Verifier::isValidUUID(const MDNode &N, const Metadata *MD) {
 
   // Keep track of names of types referenced via UUID so we can check that they
   // actually exist.
-  TypeRefs.insert(std::make_pair(S, &N));
+  UnresolvedTypeRefs.insert(std::make_pair(S, &N));
   return true;
 }
 
@@ -3386,6 +3389,71 @@ void Verifier::visitDbgIntrinsic(StringRef Kind, DbgIntrinsicTy &DII) {
          BB ? BB->getParent() : nullptr, Var, VarIA, Loc, LocIA);
 }
 
+template <class MapTy>
+static uint64_t getVariableSize(const MDLocalVariable &V, const MapTy &Map) {
+  // Be careful of broken types (checked elsewhere).
+  const Metadata *RawType = V.getRawType();
+  while (RawType) {
+    // Try to get the size directly.
+    if (auto *T = dyn_cast<MDType>(RawType))
+      if (uint64_t Size = T->getSizeInBits())
+        return Size;
+
+    if (auto *DT = dyn_cast<MDDerivedType>(RawType)) {
+      // Look at the base type.
+      RawType = DT->getRawBaseType();
+      continue;
+    }
+
+    if (auto *S = dyn_cast<MDString>(RawType)) {
+      // Don't error on missing types (checked elsewhere).
+      RawType = Map.lookup(S);
+      continue;
+    }
+
+    // Missing type or size.
+    break;
+  }
+
+  // Fail gracefully.
+  return 0;
+}
+
+template <class MapTy>
+void Verifier::verifyBitPieceExpression(const DbgInfoIntrinsic &I,
+                                        const MapTy &TypeRefs) {
+  MDLocalVariable *V;
+  MDExpression *E;
+  if (auto *DVI = dyn_cast<DbgValueInst>(&I)) {
+    V = dyn_cast_or_null<MDLocalVariable>(DVI->getRawVariable());
+    E = dyn_cast_or_null<MDExpression>(DVI->getRawExpression());
+  } else {
+    auto *DDI = cast<DbgDeclareInst>(&I);
+    V = dyn_cast_or_null<MDLocalVariable>(DDI->getRawVariable());
+    E = dyn_cast_or_null<MDExpression>(DDI->getRawExpression());
+  }
+
+  // We don't know whether this intrinsic verified correctly.
+  if (!V || !E || !E->isValid())
+    return;
+
+  // Nothing to do if this isn't a bit piece expression.
+  if (!E->isBitPiece())
+    return;
+
+  // If there's no size, the type is broken, but that should be checked
+  // elsewhere.
+  uint64_t VarSize = getVariableSize(*V, TypeRefs);
+  if (!VarSize)
+    return;
+
+  unsigned PieceSize = E->getBitPieceSize();
+  unsigned PieceOffset = E->getBitPieceOffset();
+  Assert(PieceSize + PieceOffset <= VarSize,
+         "piece is larger than or outside of variable", &I, V, E);
+  Assert(PieceSize != VarSize, "piece covers entire variable", &I, V, E);
+}
+
 void Verifier::visitUnresolvedTypeRef(const MDString *S, const MDNode *N) {
   // This is in its own function so we get an error for each bad type ref (not
   // just the first).
@@ -3397,18 +3465,35 @@ void Verifier::verifyTypeRefs() {
   if (!CUs)
     return;
 
-  // Visit all the compile units again to check the type references.
+  // Visit all the compile units again to map the type references.
+  SmallDenseMap<const MDString *, const MDType *, 32> TypeRefs;
   for (auto *CU : CUs->operands())
     if (auto Ts = cast<MDCompileUnit>(CU)->getRetainedTypes())
       for (MDType *Op : Ts)
         if (auto *T = dyn_cast<MDCompositeType>(Op))
-          TypeRefs.erase(T->getRawIdentifier());
-  if (TypeRefs.empty())
+          if (auto *S = T->getRawIdentifier()) {
+            UnresolvedTypeRefs.erase(S);
+            TypeRefs.insert(std::make_pair(S, T));
+          }
+
+  // Verify debug info intrinsic bit piece expressions.  This needs a second
+  // pass through the intructions, since we haven't built TypeRefs yet when
+  // verifying functions, and simply queuing the DbgInfoIntrinsics to evaluate
+  // later/now would queue up some that could be later deleted.
+  for (const Function &F : *M)
+    for (const BasicBlock &BB : F)
+      for (const Instruction &I : BB)
+        if (auto *DII = dyn_cast<DbgInfoIntrinsic>(&I))
+          verifyBitPieceExpression(*DII, TypeRefs);
+
+  // Return early if all typerefs were resolved.
+  if (UnresolvedTypeRefs.empty())
     return;
 
   // Sort the unresolved references by name so the output is deterministic.
   typedef std::pair<const MDString *, const MDNode *> TypeRef;
-  SmallVector<TypeRef, 32> Unresolved(TypeRefs.begin(), TypeRefs.end());
+  SmallVector<TypeRef, 32> Unresolved(UnresolvedTypeRefs.begin(),
+                                      UnresolvedTypeRefs.end());
   std::sort(Unresolved.begin(), Unresolved.end(),
             [](const TypeRef &LHS, const TypeRef &RHS) {
     return LHS.first->getString() < RHS.first->getString();

test/DebugInfo/X86/deleted-bit-piece.ll

@@ -0,0 +1,46 @@
+; RUN: llc < %s | FileCheck %s
+; This is mainly a crasher for the revert in r234717.  A debug info intrinsic
+; that gets deleted can't have its bit piece expression verified after it's
+; deleted.
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+; CHECK: __Z3foov:
+; CHECK: retq
+
+define void @_Z3foov() {
+entry:
+  br i1 undef, label %exit, label %bb
+
+bb:                                               ; preds = %entry
+  call void @llvm.dbg.value(metadata i8* undef, i64 0, metadata !15, metadata !16), !dbg !17
+  br label %exit
+
+exit:                                             ; preds = %bb, %entry
+  ret void
+}
+
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+!llvm.module.flags = !{!0, !1}
+!llvm.dbg.cu = !{!2}
+
+!0 = !{i32 2, !"Dwarf Version", i32 2}
+!1 = !{i32 2, !"Debug Info Version", i32 3}
+!2 = !MDCompileUnit(language: DW_LANG_C_plus_plus, file: !3, isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !4, retainedTypes: !5, subprograms: !11, globals: !4, imports: !4)
+!3 = !MDFile(filename: "foo.cpp", directory: "/path/to/dir")
+!4 = !{}
+!5 = !{!6}
+!6 = !MDCompositeType(tag: DW_TAG_structure_type, name: "Class", size: 64, align: 64, elements: !7, identifier: "_ZT5Class")
+!7 = !{!8, !10}
+!8 = !MDDerivedType(tag: DW_TAG_member, name: "a", scope: !"_ZT5Class", baseType: !9, size: 32, align: 32)
+!9 = !MDBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!10 = !MDDerivedType(tag: DW_TAG_member, name: "b", scope: !"_ZT5Class", baseType: !9, size: 32, align: 32)
+!11 = !{!12}
+!12 = !MDSubprogram(name: "foo", scope: null, file: !3, type: !13, isLocal: false, isDefinition: true, isOptimized: false, function: void ()* @_Z3foov)
+!13 = !MDSubroutineType(types: !14)
+!14 = !{null}
+!15 = !MDLocalVariable(tag: DW_TAG_auto_variable, name: "v", scope: !12, type: !"_ZT5Class")
+!16 = !MDExpression(DW_OP_bit_piece, 32, 32)
+!17 = !MDLocation(line: 2755, column: 9, scope: !12)