[clang][dataflow][NFC] Convert mutable vector references to ArrayRef

[li.zhe.hua]

Summary

transferBlock and computeBlockInputState only read the
BlockStates vector for the predecessor block(s), and do not need to
mutate any of the contents. Only runTypeErasedDataflowAnalysis
writes into the vector, so simply down to an ArrayRef.

[li.zhe.hua]

Bah, I think I screwed up arc at some point. This was committed as 18034aee63eeac673496a88d9e90c8dd73d15927.

clang/include/clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h

 ///
 /// Requirements:
 ///
 ///   All predecessors of `Block` except those with loop back edges must have
 ///   already been transferred. States in `BlockStates` that are set to
 ///   `llvm::None` represent basic blocks that are not evaluated yet.
 TypeErasedDataflowAnalysisState transferBlock(
     const ControlFlowContext &CFCtx,
-    std::vector<llvm::Optional<TypeErasedDataflowAnalysisState>> &BlockStates,
+    llvm::ArrayRef<llvm::Optional<TypeErasedDataflowAnalysisState>> BlockStates,
     const CFGBlock &Block, const Environment &InitEnv,
     TypeErasedDataflowAnalysis &Analysis,
     std::function<void(const CFGStmt &,
                        const TypeErasedDataflowAnalysisState &)>
         HandleTransferredStmt = nullptr);
 
 /// Performs dataflow analysis and returns a mapping from basic block IDs to
 /// dataflow analysis states that model the respective basic blocks. Indices of

clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp

 ///
 /// Requirements:
 ///
 ///   All predecessors of `Block` except those with loop back edges must have
 ///   already been transferred. States in `BlockStates` that are set to
 ///   `llvm::None` represent basic blocks that are not evaluated yet.
 static TypeErasedDataflowAnalysisState computeBlockInputState(
     const ControlFlowContext &CFCtx,
-    std::vector<llvm::Optional<TypeErasedDataflowAnalysisState>> &BlockStates,
+    llvm::ArrayRef<llvm::Optional<TypeErasedDataflowAnalysisState>> BlockStates,
     const CFGBlock &Block, const Environment &InitEnv,
     TypeErasedDataflowAnalysis &Analysis) {
   llvm::DenseSet<const CFGBlock *> Preds;
   Preds.insert(Block.pred_begin(), Block.pred_end());
   if (Block.getTerminator().isTemporaryDtorsBranch()) {
     // This handles a special case where the code that produced the CFG includes
     // a conditional operator with a branch that constructs a temporary and
     // calls a destructor annotated as noreturn. The CFG models this as follows:
static void transferCFGInitializer(const CFGInitializer &CfgInit,
   } else {
     auto &MemberLoc = ThisLoc.getChild(*Member);
     State.Env.setValue(MemberLoc, *InitStmtVal);
   }
 }
 
 TypeErasedDataflowAnalysisState transferBlock(
     const ControlFlowContext &CFCtx,
-    std::vector<llvm::Optional<TypeErasedDataflowAnalysisState>> &BlockStates,
+    llvm::ArrayRef<llvm::Optional<TypeErasedDataflowAnalysisState>> BlockStates,
     const CFGBlock &Block, const Environment &InitEnv,
     TypeErasedDataflowAnalysis &Analysis,
     std::function<void(const CFGStmt &,
                        const TypeErasedDataflowAnalysisState &)>
         HandleTransferredStmt) {
   TypeErasedDataflowAnalysisState State =
       computeBlockInputState(CFCtx, BlockStates, Block, InitEnv, Analysis);
   for (const CFGElement &Element : Block) {