[Bitcode] Check for type mismatch when assigning value

If the value is forward-declared, then the type must match,
otherwise we can't RAUW.

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -2511,9 +2511,10 @@ Error BitcodeReader::parseConstants() {
         SmallVector<int, 16> Mask;
         ShuffleVectorInst::getShuffleMask(Op2, Mask);
         Value *V = ConstantExpr::getShuffleVector(Op0, Op1, Mask);
-        ValueList.assignValue(
-            CstNo, V,
-            getVirtualTypeID(V->getType(), getContainedTypeID(OpTyID)));
+        if (Error Err = ValueList.assignValue(
+                CstNo, V,
+                getVirtualTypeID(V->getType(), getContainedTypeID(OpTyID))))
+          return Err;
       }
       for (auto &DelayedSelector : DelayedSelectors) {
         Type *OpTy = DelayedSelector.OpTy;
@@ -2539,7 +2540,8 @@ Error BitcodeReader::parseConstants() {
         Constant *Op0 =
             ValueList.getConstantFwdRef(Op0Idx, SelectorTy, SelectorTyID);
         Value *V = ConstantExpr::getSelect(Op0, Op1, Op2);
-        ValueList.assignValue(CstNo, V, OpTyID);
+        if (Error Err = ValueList.assignValue(CstNo, V, OpTyID))
+          return Err;
       }
 
       if (NextCstNo != ValueList.size())
@@ -3146,7 +3148,8 @@ Error BitcodeReader::parseConstants() {
     }
 
     assert(V->getType() == getTypeByID(CurTyID) && "Incorrect result type ID");
-    ValueList.assignValue(NextCstNo, V, CurTyID);
+    if (Error Err = ValueList.assignValue(NextCstNo, V, CurTyID))
+      return Err;
     ++NextCstNo;
   }
 }
@@ -5880,7 +5883,8 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
     if (!I->getType()->isVoidTy()) {
       assert(I->getType() == getTypeByID(ResTypeID) &&
              "Incorrect result type ID");
-      ValueList.assignValue(NextValueNo++, I, ResTypeID);
+      if (Error Err = ValueList.assignValue(NextValueNo++, I, ResTypeID))
+        return Err;
     }
   }
 

llvm/lib/Bitcode/Reader/ValueList.cpp

@@ -17,6 +17,7 @@
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Support/Casting.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <cstddef>
 
@@ -60,11 +61,11 @@ DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantPlaceHolder, Value)
 
 } // end namespace llvm
 
-void BitcodeReaderValueList::assignValue(unsigned Idx, Value *V,
-                                         unsigned TypeID) {
+Error BitcodeReaderValueList::assignValue(unsigned Idx, Value *V,
+                                          unsigned TypeID) {
   if (Idx == size()) {
     push_back(V, TypeID);
-    return;
+    return Error::success();
   }
 
   if (Idx >= size())
@@ -74,7 +75,7 @@ void BitcodeReaderValueList::assignValue(unsigned Idx, Value *V,
   if (!Old.first) {
     Old.first = V;
     Old.second = TypeID;
-    return;
+    return Error::success();
   }
 
   // Handle constants and non-constants (e.g. instrs) differently for
@@ -86,9 +87,14 @@ void BitcodeReaderValueList::assignValue(unsigned Idx, Value *V,
   } else {
     // If there was a forward reference to this value, replace it.
     Value *PrevVal = Old.first;
+    if (PrevVal->getType() != V->getType())
+      return createStringError(
+          std::errc::illegal_byte_sequence,
+          "Assigned value does not match type of forward declaration");
     Old.first->replaceAllUsesWith(V);
     PrevVal->deleteValue();
   }
+  return Error::success();
 }
 
 Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx, Type *Ty,

llvm/lib/Bitcode/Reader/ValueList.h

@@ -21,6 +21,7 @@
 namespace llvm {
 
 class Constant;
+class Error;
 class LLVMContext;
 class Type;
 class Value;
@@ -92,7 +93,7 @@ public:
   Constant *getConstantFwdRef(unsigned Idx, Type *Ty, unsigned TyID);
   Value *getValueFwdRef(unsigned Idx, Type *Ty, unsigned TyID);
 
-  void assignValue(unsigned Idx, Value *V, unsigned TypeID);
+  Error assignValue(unsigned Idx, Value *V, unsigned TypeID);
 
   /// Once all constants are read, this method bulk resolves any forward
   /// references.

llvm/test/Bitcode/invalid.test

@@ -296,3 +296,7 @@ RUN: not llvm-dis -disable-output -opaque-pointers %p/Inputs/missing-element-typ
 RUN:   FileCheck --check-prefix=MISSING-ELEMENT-TYPE-FOR-ATTRIBUTE %s
 
 MISSING-ELEMENT-TYPE-FOR-ATTRIBUTE: Missing element type for typed attribute upgrade
+RUN: not llvm-dis -disable-output -opaque-pointers %p/Inputs/invalid-forward-declare.bc 2>&1 | \
+RUN:   FileCheck --check-prefix=INVALID-FORWARD-DECLARE %s
+
+INVALID-FORWARD-DECLARE: Assigned value does not match type of forward declaration