Reapply "[IR] Move optional data in llvm::Function into a hungoff uselist"

Make personality functions, prefix data, and prologue data hungoff
operands of Function.

This is based on the email thread "[RFC] Clean up the way we store
optional Function data" on llvm-dev.

Thanks to sanjoyd, majnemer, rnk, loladiro, and dexonsmith for feedback!

Includes a fix to scrub value subclass data in dropAllReferences.

Differential Revision: http://reviews.llvm.org/D13829

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256093 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 20 insertions, 24 deletions

diff --git a/include/llvm/IR/Function.h b/include/llvm/IR/Function.h
index 2843cf2cce3..2a983930bf4 100644
--- a/include/llvm/IR/Function.h
+++ b/include/llvm/IR/Function.h
@@ -64,7 +64,7 @@ private:
    * bit 0      : HasLazyArguments
    * bit 1      : HasPrefixData
    * bit 2      : HasPrologueData
-   * bit 3      : [reserved]
+   * bit 3      : HasPersonalityFn
    * bits 4-13  : CallingConvention
    * bits 14-15 : [reserved]
    */
@@ -110,7 +110,7 @@ private:
 public:
   static Function *Create(FunctionType *Ty, LinkageTypes Linkage,
                           const Twine &N = "", Module *M = nullptr) {
-    return new(1) Function(Ty, Linkage, N, M);
+    return new Function(Ty, Linkage, N, M);
   }
 
   ~Function() override;
@@ -118,14 +118,6 @@ public:
   /// \brief Provide fast operand accessors
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
-  /// \brief Get the personality function associated with this function.
-  bool hasPersonalityFn() const { return getNumOperands() != 0; }
-  Constant *getPersonalityFn() const {
-    assert(hasPersonalityFn());
-    return cast<Constant>(Op<0>());
-  }
-  void setPersonalityFn(Constant *C);
-
   Type *getReturnType() const;           // Return the type of the ret val
   FunctionType *getFunctionType() const; // Return the FunctionType for me
 
@@ -525,17 +517,30 @@ public:
   size_t arg_size() const;
   bool arg_empty() const;
 
+  /// \brief Check whether this function has a personality function.
+  bool hasPersonalityFn() const {
+    return getSubclassDataFromValue() & (1<<3);
+  }
+
+  /// \brief Get the personality function associated with this function.
+  Constant *getPersonalityFn() const;
+  void setPersonalityFn(Constant *Fn);
+
+  /// \brief Check whether this function has prefix data.
   bool hasPrefixData() const {
     return getSubclassDataFromValue() & (1<<1);
   }
 
+  /// \brief Get the prefix data associated with this function.
   Constant *getPrefixData() const;
   void setPrefixData(Constant *PrefixData);
 
+  /// \brief Check whether this function has prologue data.
   bool hasPrologueData() const {
     return getSubclassDataFromValue() & (1<<2);
   }
 
+  /// \brief Get the prologue data associated with this function.
   Constant *getPrologueData() const;
   void setPrologueData(Constant *PrologueData);
 
@@ -630,11 +635,15 @@ public:
   DISubprogram *getSubprogram() const;
 
 private:
+  void allocHungoffUselist();
+  template<int Idx> void setHungoffOperand(Constant *C);
+
   // Shadow Value::setValueSubclassData with a private forwarding method so that
   // subclasses cannot accidentally use it.
   void setValueSubclassData(unsigned short D) {
     Value::setValueSubclassData(D);
   }
+  void setValueSubclassDataBit(unsigned Bit, bool On);
 
   bool hasMetadataHashEntry() const {
     return getGlobalObjectSubClassData() & HasMetadataHashEntryBit;
@@ -647,7 +656,7 @@ private:
 };
 
 template <>
-struct OperandTraits<Function> : public OptionalOperandTraits<Function> {};
+struct OperandTraits<Function> : public HungoffOperandTraits<3> {};
 
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(Function, Value)
 
diff --git a/include/llvm/IR/User.h b/include/llvm/IR/User.h
index 639dc5c01c8..885ae197d22 100644
--- a/include/llvm/IR/User.h
+++ b/include/llvm/IR/User.h
@@ -170,19 +170,6 @@ public:
     NumUserOperands = NumOps;
   }
 
-  /// Set the number of operands on a Function.
-  ///
-  /// Function always allocates space for a single operands, but
-  /// doesn't always use it.
-  ///
-  /// FIXME: As that the number of operands is used to find the start of
-  /// the allocated memory in operator delete, we need to always think we have
-  /// 1 operand before delete.
-  void setFunctionNumOperands(unsigned NumOps) {
-    assert(NumOps <= 1 && "Function can only have 0 or 1 operands");
-    NumUserOperands = NumOps;
-  }
-
   /// \brief Subclasses with hung off uses need to manage the operand count
   /// themselves.  In these instances, the operand count isn't used to find the
   /// OperandList, so there's no issue in having the operand count change.