Split GlobalValue into GlobalValue and GlobalObject.

This allows code to statically accept a Function or a GlobalVariable, but
not an alias. This is already a cleanup by itself IMHO, but the main
reason for it is that it gives a lot more confidence that the refactoring to fix
the design of GlobalAlias is correct. That will be a followup patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208716 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm-c/Core.h

@@ -1173,9 +1173,10 @@ LLVMTypeRef LLVMX86MMXType(void);
       macro(ConstantStruct)                 \
       macro(ConstantVector)                 \
       macro(GlobalValue)                    \
-        macro(Function)                     \
         macro(GlobalAlias)                  \
-        macro(GlobalVariable)               \
+        macro(GlobalObject)                 \
+          macro(Function)                   \
+          macro(GlobalVariable)             \
       macro(UndefValue)                     \
     macro(Instruction)                      \
       macro(BinaryOperator)                 \

include/llvm/CodeGen/AsmPrinter.h

@@ -233,7 +233,7 @@ public:
   /// requested, it will override the alignment request if required for
   /// correctness.
   ///
-  void EmitAlignment(unsigned NumBits, const GlobalValue *GV = nullptr) const;
+  void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
 
   /// This method prints the label for the specified MachineBasicBlock, an
   /// alignment (if present) and a comment describing it if appropriate.

include/llvm/IR/Function.h

@@ -23,7 +23,7 @@
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CallingConv.h"
-#include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/GlobalObject.h"
 #include "llvm/Support/Compiler.h"
 
 namespace llvm {
@@ -68,7 +68,7 @@ private:
   mutable ilist_half_node<Argument> Sentinel;
 };
 
-class Function : public GlobalValue, public ilist_node<Function> {
+class Function : public GlobalObject, public ilist_node<Function> {
 public:
   typedef iplist<Argument> ArgumentListType;
   typedef iplist<BasicBlock> BasicBlockListType;

include/llvm/IR/GlobalAlias.h

@@ -68,8 +68,8 @@ public:
   /// This method tries to ultimately resolve the alias by going through the
   /// aliasing chain and trying to find the very last global. Returns NULL if a
   /// cycle was found.
-  GlobalValue *getAliasedGlobal();
-  const GlobalValue *getAliasedGlobal() const {
+  GlobalObject *getAliasedGlobal();
+  const GlobalObject *getAliasedGlobal() const {
     return const_cast<GlobalAlias *>(this)->getAliasedGlobal();
   }
 

include/llvm/IR/GlobalObject.h

@@ -0,0 +1,58 @@
+//===-- llvm/GlobalObject.h - Class to represent a global object *- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This represents an independent object. That is, a function or a global
+// variable, but not an alias.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_GLOBALOBJECT_H
+#define LLVM_IR_GLOBALOBJECT_H
+
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/GlobalValue.h"
+
+namespace llvm {
+
+class Module;
+
+class GlobalObject : public GlobalValue {
+  GlobalObject(const GlobalObject &) LLVM_DELETED_FUNCTION;
+
+protected:
+  GlobalObject(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
+               LinkageTypes Linkage, const Twine &Name)
+      : GlobalValue(Ty, VTy, Ops, NumOps, Linkage, Name) {
+    setGlobalValueSubClassData(0);
+  }
+
+  std::string Section;     // Section to emit this into, empty means default
+public:
+  unsigned getAlignment() const {
+    return (1u << getGlobalValueSubClassData()) >> 1;
+  }
+  void setAlignment(unsigned Align);
+
+  bool hasSection() const { return !getSection().empty(); }
+  const std::string &getSection() const { return Section; }
+  void setSection(StringRef S);
+
+  void copyAttributesFrom(const GlobalValue *Src) override;
+
+  // Methods for support type inquiry through isa, cast, and dyn_cast:
+  static inline bool classof(const Value *V) {
+    return V->getValueID() == Value::FunctionVal ||
+           V->getValueID() == Value::GlobalVariableVal;
+  }
+};
+
+} // End llvm namespace
+
+#endif

include/llvm/IR/GlobalValue.h

@@ -62,7 +62,7 @@ protected:
   GlobalValue(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
               LinkageTypes Linkage, const Twine &Name)
       : Constant(Ty, VTy, Ops, NumOps), Linkage(Linkage),
-        Visibility(DefaultVisibility), Alignment(0), UnnamedAddr(0),
+        Visibility(DefaultVisibility), UnnamedAddr(0),
         DllStorageClass(DefaultStorageClass), Parent(nullptr) {
     setName(Name);
   }
@@ -71,18 +71,29 @@ protected:
   // Linkage and Visibility from turning into negative values.
   LinkageTypes Linkage : 5;   // The linkage of this global
   unsigned Visibility : 2;    // The visibility style of this global
-  unsigned Alignment : 16;    // Alignment of this symbol, must be power of two
   unsigned UnnamedAddr : 1;   // This value's address is not significant
   unsigned DllStorageClass : 2; // DLL storage class
+
+private:
+  // Give subclasses access to what otherwise would be wasted padding.
+  // (22 + 2 + 1 + 2 + 5) == 32.
+  unsigned SubClassData : 22;
+protected:
+  unsigned getGlobalValueSubClassData() const {
+    return SubClassData;
+  }
+  void setGlobalValueSubClassData(unsigned V) {
+    assert(V < (1 << 22) && "It will not fit");
+    SubClassData = V;
+  }
+
   Module *Parent;             // The containing module.
-  std::string Section;        // Section to emit this into, empty mean default
 public:
   ~GlobalValue() {
     removeDeadConstantUsers();   // remove any dead constants using this.
   }
 
   unsigned getAlignment() const;
-  void setAlignment(unsigned Align);
 
   bool hasUnnamedAddr() const { return UnnamedAddr; }
   void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
@@ -112,7 +123,6 @@ public:
 
   bool hasSection() const { return !getSection().empty(); }
   const std::string &getSection() const;
-  void setSection(StringRef S);
 
   /// Global values are always pointers.
   inline PointerType *getType() const {

include/llvm/IR/GlobalVariable.h

@@ -22,7 +22,7 @@
 
 #include "llvm/ADT/Twine.h"
 #include "llvm/ADT/ilist_node.h"
-#include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/OperandTraits.h"
 
 namespace llvm {
@@ -32,7 +32,7 @@ class Constant;
 template<typename ValueSubClass, typename ItemParentClass>
   class SymbolTableListTraits;
 
-class GlobalVariable : public GlobalValue, public ilist_node<GlobalVariable> {
+class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
   friend class SymbolTableListTraits<GlobalVariable, Module>;
   void *operator new(size_t, unsigned) LLVM_DELETED_FUNCTION;
   void operator=(const GlobalVariable &) LLVM_DELETED_FUNCTION;

include/llvm/IR/Value.h

@@ -31,6 +31,7 @@ class Constant;
 class DataLayout;
 class Function;
 class GlobalAlias;
+class GlobalObject;
 class GlobalValue;
 class GlobalVariable;
 class InlineAsm;
@@ -526,8 +527,13 @@ template <> struct isa_impl<GlobalAlias, Value> {
 
 template <> struct isa_impl<GlobalValue, Value> {
   static inline bool doit(const Value &Val) {
-    return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
-      isa<GlobalAlias>(Val);
+    return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
+  }
+};
+
+template <> struct isa_impl<GlobalObject, Value> {
+  static inline bool doit(const Value &Val) {
+    return isa<GlobalVariable>(Val) || isa<Function>(Val);
   }
 };
 

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1458,7 +1458,7 @@ void AsmPrinter::EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
 // an explicit alignment requested, it will override the alignment request
 // if required for correctness.
 //
-void AsmPrinter::EmitAlignment(unsigned NumBits, const GlobalValue *GV) const {
+void AsmPrinter::EmitAlignment(unsigned NumBits, const GlobalObject *GV) const {
   if (GV) NumBits = getGVAlignmentLog2(GV, *TM.getDataLayout(), NumBits);
 
   if (NumBits == 0) return;   // 1-byte aligned: no need to emit alignment.

lib/IR/Core.cpp

@@ -1307,7 +1307,7 @@ const char *LLVMGetSection(LLVMValueRef Global) {
 }
 
 void LLVMSetSection(LLVMValueRef Global, const char *Section) {
-  unwrap<GlobalValue>(Global)->setSection(Section);
+  unwrap<GlobalObject>(Global)->setSection(Section);
 }
 
 LLVMVisibility LLVMGetVisibility(LLVMValueRef Global) {
@@ -1357,7 +1357,7 @@ unsigned LLVMGetAlignment(LLVMValueRef V) {
 
 void LLVMSetAlignment(LLVMValueRef V, unsigned Bytes) {
   Value *P = unwrap<Value>(V);
-  if (GlobalValue *GV = dyn_cast<GlobalValue>(P))
+  if (GlobalObject *GV = dyn_cast<GlobalObject>(P))
     GV->setAlignment(Bytes);
   else if (AllocaInst *AI = dyn_cast<AllocaInst>(P))
     AI->setAlignment(Bytes);

lib/IR/Function.cpp

@@ -209,7 +209,7 @@ void Function::eraseFromParent() {
 
 Function::Function(FunctionType *Ty, LinkageTypes Linkage,
                    const Twine &name, Module *ParentModule)
-  : GlobalValue(PointerType::getUnqual(Ty),
+  : GlobalObject(PointerType::getUnqual(Ty),
                 Value::FunctionVal, nullptr, 0, Linkage, name) {
   assert(FunctionType::isValidReturnType(getReturnType()) &&
          "invalid return type");
@@ -361,7 +361,7 @@ void Function::clearGC() {
 /// create a Function) from the Function Src to this one.
 void Function::copyAttributesFrom(const GlobalValue *Src) {
   assert(isa<Function>(Src) && "Expected a Function!");
-  GlobalValue::copyAttributesFrom(Src);
+  GlobalObject::copyAttributesFrom(Src);
   const Function *SrcF = cast<Function>(Src);
   setCallingConv(SrcF->getCallingConv());
   setAttributes(SrcF->getAttributes());

lib/IR/Globals.cpp

@@ -53,11 +53,6 @@ void GlobalValue::destroyConstant() {
 /// copyAttributesFrom - copy all additional attributes (those not needed to
 /// create a GlobalValue) from the GlobalValue Src to this one.
 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) {
-  if (!isa<GlobalAlias>(this)) {
-    setAlignment(Src->getAlignment());
-    setSection(Src->getSection());
-  }
-
   setVisibility(Src->getVisibility());
   setUnnamedAddr(Src->hasUnnamedAddr());
   setDLLStorageClass(Src->getDLLStorageClass());
@@ -67,29 +62,31 @@ unsigned GlobalValue::getAlignment() const {
   if (auto *GA = dyn_cast<GlobalAlias>(this))
     return GA->getAliasedGlobal()->getAlignment();
 
-  return (1u << Alignment) >> 1;
+  return cast<GlobalObject>(this)->getAlignment();
 }
 
-void GlobalValue::setAlignment(unsigned Align) {
-  assert((!isa<GlobalAlias>(this)) &&
-         "GlobalAlias should not have an alignment!");
+void GlobalObject::setAlignment(unsigned Align) {
   assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
   assert(Align <= MaximumAlignment &&
          "Alignment is greater than MaximumAlignment!");
-  Alignment = Log2_32(Align) + 1;
+  setGlobalValueSubClassData(Log2_32(Align) + 1);
   assert(getAlignment() == Align && "Alignment representation error!");
 }
 
+void GlobalObject::copyAttributesFrom(const GlobalValue *Src) {
+  const auto *GV = cast<GlobalObject>(Src);
+  GlobalValue::copyAttributesFrom(GV);
+  setAlignment(GV->getAlignment());
+  setSection(GV->getSection());
+}
+
 const std::string &GlobalValue::getSection() const {
   if (auto *GA = dyn_cast<GlobalAlias>(this))
     return GA->getAliasedGlobal()->getSection();
-  return Section;
+  return cast<GlobalObject>(this)->getSection();
 }
 
-void GlobalValue::setSection(StringRef S) {
-  assert(!isa<GlobalAlias>(this) && "GlobalAlias should not have a section!");
-  Section = S;
-}
+void GlobalObject::setSection(StringRef S) { Section = S; }
 
 bool GlobalValue::isDeclaration() const {
   // Globals are definitions if they have an initializer.
@@ -113,9 +110,9 @@ GlobalVariable::GlobalVariable(Type *Ty, bool constant, LinkageTypes Link,
                                Constant *InitVal, const Twine &Name,
                                ThreadLocalMode TLMode, unsigned AddressSpace,
                                bool isExternallyInitialized)
-    : GlobalValue(PointerType::get(Ty, AddressSpace), Value::GlobalVariableVal,
-                  OperandTraits<GlobalVariable>::op_begin(this),
-                  InitVal != nullptr, Link, Name),
+    : GlobalObject(PointerType::get(Ty, AddressSpace), Value::GlobalVariableVal,
+                   OperandTraits<GlobalVariable>::op_begin(this),
+                   InitVal != nullptr, Link, Name),
       isConstantGlobal(constant), threadLocalMode(TLMode),
       isExternallyInitializedConstant(isExternallyInitialized) {
   if (InitVal) {
@@ -132,9 +129,9 @@ GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant,
                                const Twine &Name, GlobalVariable *Before,
                                ThreadLocalMode TLMode, unsigned AddressSpace,
                                bool isExternallyInitialized)
-    : GlobalValue(PointerType::get(Ty, AddressSpace), Value::GlobalVariableVal,
-                  OperandTraits<GlobalVariable>::op_begin(this),
-                  InitVal != nullptr, Link, Name),
+    : GlobalObject(PointerType::get(Ty, AddressSpace), Value::GlobalVariableVal,
+                   OperandTraits<GlobalVariable>::op_begin(this),
+                   InitVal != nullptr, Link, Name),
       isConstantGlobal(constant), threadLocalMode(TLMode),
       isExternallyInitializedConstant(isExternallyInitialized) {
   if (InitVal) {
@@ -206,7 +203,7 @@ void GlobalVariable::setInitializer(Constant *InitVal) {
 /// create a GlobalVariable) from the GlobalVariable Src to this one.
 void GlobalVariable::copyAttributesFrom(const GlobalValue *Src) {
   assert(isa<GlobalVariable>(Src) && "Expected a GlobalVariable!");
-  GlobalValue::copyAttributesFrom(Src);
+  GlobalObject::copyAttributesFrom(Src);
   const GlobalVariable *SrcVar = cast<GlobalVariable>(Src);
   setThreadLocalMode(SrcVar->getThreadLocalMode());
 }
@@ -269,7 +266,7 @@ static GlobalValue *getAliaseeGV(GlobalAlias *GA) {
   return cast<GlobalValue>(CE->getOperand(0));
 }
 
-GlobalValue *GlobalAlias::getAliasedGlobal() {
+GlobalObject *GlobalAlias::getAliasedGlobal() {
   SmallPtrSet<GlobalValue*, 3> Visited;
 
   GlobalAlias *GA = this;
@@ -282,6 +279,6 @@ GlobalValue *GlobalAlias::getAliasedGlobal() {
     // Iterate over aliasing chain.
     GA = dyn_cast<GlobalAlias>(GV);
     if (!GA)
-      return GV;
+      return cast<GlobalObject>(GV);
   }
 }

lib/Linker/LinkModules.cpp

@@ -495,15 +495,15 @@ static void forceRenaming(GlobalValue *GV, StringRef Name) {
 /// a GlobalValue) from the SrcGV to the DestGV.
 static void copyGVAttributes(GlobalValue *DestGV, const GlobalValue *SrcGV) {
   // Use the maximum alignment, rather than just copying the alignment of SrcGV.
+  auto *DestGO = dyn_cast<GlobalObject>(DestGV);
   unsigned Alignment;
-  bool IsAlias = isa<GlobalAlias>(DestGV);
-  if (!IsAlias)
-    Alignment = std::max(DestGV->getAlignment(), SrcGV->getAlignment());
+  if (DestGO)
+    Alignment = std::max(DestGO->getAlignment(), SrcGV->getAlignment());
 
   DestGV->copyAttributesFrom(SrcGV);
 
-  if (!IsAlias)
-    DestGV->setAlignment(Alignment);
+  if (DestGO)
+    DestGO->setAlignment(Alignment);
 
   forceRenaming(DestGV, SrcGV->getName());
 }

lib/Transforms/Utils/Local.cpp

@@ -896,26 +896,26 @@ static unsigned enforceKnownAlignment(Value *V, unsigned Align,
     return PrefAlign;
   }
 
-  if (auto *GV = dyn_cast<GlobalValue>(V)) {
+  if (auto *GO = dyn_cast<GlobalObject>(V)) {
     // If there is a large requested alignment and we can, bump up the alignment
     // of the global.
-    if (GV->isDeclaration())
+    if (GO->isDeclaration())
       return Align;
     // If the memory we set aside for the global may not be the memory used by
     // the final program then it is impossible for us to reliably enforce the
     // preferred alignment.
-    if (GV->isWeakForLinker())
+    if (GO->isWeakForLinker())
       return Align;
 
-    if (GV->getAlignment() >= PrefAlign)
-      return GV->getAlignment();
+    if (GO->getAlignment() >= PrefAlign)
+      return GO->getAlignment();
     // We can only increase the alignment of the global if it has no alignment
     // specified or if it is not assigned a section.  If it is assigned a
     // section, the global could be densely packed with other objects in the
     // section, increasing the alignment could cause padding issues.
-    if (!GV->hasSection() || GV->getAlignment() == 0)
-      GV->setAlignment(PrefAlign);
-    return GV->getAlignment();
+    if (!GO->hasSection() || GO->getAlignment() == 0)
+      GO->setAlignment(PrefAlign);
+    return GO->getAlignment();
   }
 
   return Align;