[Function] Clean up {prefix,prologue} data routines (NFC)

[vsk]

Summary

Factor out some common code used to get+set function prefix/prologue
data. This may come in handy if we ever decide to store personality
functions in the same way we store prefix/prologue data.

Also, update the number of bits to reflect how many we actually use to
store calling convention identifiers.

[vsk]

ping

[vsk]

• Removed unrelated comment update about calling convention bits.
• Added doc comment to setFunctionData().
• Annotated calls to setFunctionData() with /*Bit=*/ comments.

Reviewed by bogner and closed by ec871634e.

[vsk]

Closing old review.

include/llvm/IR/Function.h

private:
   FunctionType *Ty;
 
   /*
    * Value::SubclassData
    *
    * bit 0  : HasLazyArguments
    * bit 1  : HasPrefixData
    * bit 2  : HasPrologueData
-   * bit 3-6: CallingConvention
+   * bit 3-9: CallingConvention
    */
 
   /// Bits from GlobalObject::GlobalObjectSubclassData.
   enum {
     /// Whether this function is materializable.
     IsMaterializableBit = 1 << 0,
     HasMetadataHashEntryBit = 1 << 1
   };

lib/IR/Function.cpp

     ImmutableCallSite CS(&*I);
     if (CS && CS.hasFnAttr(Attribute::ReturnsTwice))
       return true;
   }
 
   return false;
 }
 
+static Constant *
+getFunctionData(const Function *F,
+                const LLVMContextImpl::FunctionDataMapTy &Map) {
+  const auto &Entry = Map.find(F);
+  assert(Entry != Map.end());
+  return cast<Constant>(Entry->second->getReturnValue());
+}
+
+static unsigned setFunctionData(Function *F,
+                                LLVMContextImpl::FunctionDataMapTy &Map,
+                                Constant *Data, unsigned SCData, unsigned Bit) {
+  ReturnInst *&Holder = Map[F];
+  if (Data) {
+    if (Holder)
+      Holder->setOperand(0, Data);
+    else
+      Holder = ReturnInst::Create(F->getContext(), Data);
+    return SCData | (1 << Bit);
+  } else {
+    delete Holder;
+    Map.erase(F);
+    return SCData & ~(1 << Bit);
+  }
+}
+
 Constant *Function::getPrefixData() const {
   assert(hasPrefixData());
-  const LLVMContextImpl::PrefixDataMapTy &PDMap =
-      getContext().pImpl->PrefixDataMap;
-  assert(PDMap.find(this) != PDMap.end());
-  return cast<Constant>(PDMap.find(this)->second->getReturnValue());
+  return getFunctionData(this, getContext().pImpl->PrefixDataMap);
 }
 
 void Function::setPrefixData(Constant *PrefixData) {
   if (!PrefixData && !hasPrefixData())
     return;
 
   unsigned SCData = getSubclassDataFromValue();
-  LLVMContextImpl::PrefixDataMapTy &PDMap = getContext().pImpl->PrefixDataMap;
-  ReturnInst *&PDHolder = PDMap[this];
-  if (PrefixData) {
-    if (PDHolder)
-      PDHolder->setOperand(0, PrefixData);
-    else
-      PDHolder = ReturnInst::Create(getContext(), PrefixData);
-    SCData |= (1<<1);
-  } else {
-    delete PDHolder;
-    PDMap.erase(this);
-    SCData &= ~(1<<1);
-  }
+  SCData = setFunctionData(this, getContext().pImpl->PrefixDataMap, PrefixData,
+                           SCData, 1);
   setValueSubclassData(SCData);
 }
 
 Constant *Function::getPrologueData() const {
   assert(hasPrologueData());
-  const LLVMContextImpl::PrologueDataMapTy &SOMap =
-      getContext().pImpl->PrologueDataMap;
-  assert(SOMap.find(this) != SOMap.end());
-  return cast<Constant>(SOMap.find(this)->second->getReturnValue());
+  return getFunctionData(this, getContext().pImpl->PrologueDataMap);
 }
 
 void Function::setPrologueData(Constant *PrologueData) {
   if (!PrologueData && !hasPrologueData())
     return;
 
-  unsigned PDData = getSubclassDataFromValue();
-  LLVMContextImpl::PrologueDataMapTy &PDMap = getContext().pImpl->PrologueDataMap;
-  ReturnInst *&PDHolder = PDMap[this];
-  if (PrologueData) {
-    if (PDHolder)
-      PDHolder->setOperand(0, PrologueData);
-    else
-      PDHolder = ReturnInst::Create(getContext(), PrologueData);
-    PDData |= (1<<2);
-  } else {
-    delete PDHolder;
-    PDMap.erase(this);
-    PDData &= ~(1<<2);
-  }
-  setValueSubclassData(PDData);
+  unsigned SCData = getSubclassDataFromValue();
+  SCData = setFunctionData(this, getContext().pImpl->PrologueDataMap,
+                           PrologueData, SCData, 2);
+  setValueSubclassData(SCData);
 }
 
 void Function::setEntryCount(uint64_t Count) {
   MDBuilder MDB(getContext());
   setMetadata(LLVMContext::MD_prof, MDB.createFunctionEntryCount(Count));
 }
 
 Optional<uint64_t> Function::getEntryCount() const {

lib/IR/LLVMContextImpl.h

   /// Collection of per-function metadata used in this context.
   DenseMap<const Function *, MDAttachmentMap> FunctionMetadata;
 
   /// DiscriminatorTable - This table maps file:line locations to an
   /// integer representing the next DWARF path discriminator to assign to
   /// instructions in different blocks at the same location.
   DenseMap<std::pair<const char *, unsigned>, unsigned> DiscriminatorTable;
 
+  typedef DenseMap<const Function *, ReturnInst *> FunctionDataMapTy;
+
   /// \brief Mapping from a function to its prefix data, which is stored as the
   /// operand of an unparented ReturnInst so that the prefix data has a Use.
-  typedef DenseMap<const Function *, ReturnInst *> PrefixDataMapTy;
-  PrefixDataMapTy PrefixDataMap;
+  FunctionDataMapTy PrefixDataMap;
 
   /// \brief Mapping from a function to its prologue data, which is stored as
   /// the operand of an unparented ReturnInst so that the prologue data has a
   /// Use.
-  typedef DenseMap<const Function *, ReturnInst *> PrologueDataMapTy;
-  PrologueDataMapTy PrologueDataMap;
+  FunctionDataMapTy PrologueDataMap;
 
   int getOrAddScopeRecordIdxEntry(MDNode *N, int ExistingIdx);
   int getOrAddScopeInlinedAtIdxEntry(MDNode *Scope, MDNode *IA,int ExistingIdx);
 
   LLVMContextImpl(LLVMContext &C);
   ~LLVMContextImpl();
 
   /// Destroy the ConstantArrays if they are not used.
   void dropTriviallyDeadConstantArrays();
 };
 
 }
 
 #endif