[clang][CodeGen] Introduce class RawAddress and modify Address in

preparation for adding information to it that is needed for pointer
authentication

Author: ahatanak

clang/lib/CodeGen/ABIInfoImpl.cpp

@@ -187,7 +187,7 @@ CodeGen::emitVoidPtrDirectVAArg(CodeGenFunction &CGF, Address VAListAddr,
   CharUnits FullDirectSize = DirectSize.alignTo(SlotSize);
   Address NextPtr =
       CGF.Builder.CreateConstInBoundsByteGEP(Addr, FullDirectSize, "argp.next");
-  CGF.Builder.CreateStore(NextPtr.getPointer(), VAListAddr);
+  CGF.Builder.CreateStore(NextPtr.getRawPointer(CGF), VAListAddr);
 
   // If the argument is smaller than a slot, and this is a big-endian
   // target, the argument will be right-adjusted in its slot.
@@ -239,8 +239,8 @@ Address CodeGen::emitMergePHI(CodeGenFunction &CGF, Address Addr1,
                               const llvm::Twine &Name) {
   assert(Addr1.getType() == Addr2.getType());
   llvm::PHINode *PHI = CGF.Builder.CreatePHI(Addr1.getType(), 2, Name);
-  PHI->addIncoming(Addr1.getPointer(), Block1);
-  PHI->addIncoming(Addr2.getPointer(), Block2);
+  PHI->addIncoming(Addr1.getRawPointer(CGF), Block1);
+  PHI->addIncoming(Addr2.getRawPointer(CGF), Block2);
   CharUnits Align = std::min(Addr1.getAlignment(), Addr2.getAlignment());
   return Address(PHI, Addr1.getElementType(), Align);
 }
@@ -400,7 +400,7 @@ Address CodeGen::EmitVAArgInstr(CodeGenFunction &CGF, Address VAListAddr,
     llvm::Type *ElementTy = CGF.ConvertTypeForMem(Ty);
     llvm::Type *BaseTy = llvm::PointerType::getUnqual(ElementTy);
     llvm::Value *Addr =
-        CGF.Builder.CreateVAArg(VAListAddr.getPointer(), BaseTy);
+        CGF.Builder.CreateVAArg(VAListAddr.getRawPointer(CGF), BaseTy);
     return Address(Addr, ElementTy, TyAlignForABI);
   } else {
     assert((AI.isDirect() || AI.isExtend()) &&
@@ -416,7 +416,7 @@ Address CodeGen::EmitVAArgInstr(CodeGenFunction &CGF, Address VAListAddr,
            "Unexpected CoerceToType seen in arginfo in generic VAArg emitter!");
 
     Address Temp = CGF.CreateMemTemp(Ty, "varet");
-    Val = CGF.Builder.CreateVAArg(VAListAddr.getPointer(),
+    Val = CGF.Builder.CreateVAArg(VAListAddr.getRawPointer(CGF),
                                   CGF.ConvertTypeForMem(Ty));
     CGF.Builder.CreateStore(Val, Temp);
     return Temp;

clang/lib/CodeGen/Address.h

@@ -15,35 +15,49 @@
 #define LLVM_CLANG_LIB_CODEGEN_ADDRESS_H
 
 #include "clang/AST/CharUnits.h"
+#include "clang/AST/Type.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/Support/MathExtras.h"
 
 namespace clang {
 namespace CodeGen {
 
+class Address;
+class CGBuilderTy;
+class CodeGenFunction;
+class CodeGenModule;
+
 // Indicates whether a pointer is known not to be null.
 enum KnownNonNull_t { NotKnownNonNull, KnownNonNull };
 
-/// An aligned address.
-class Address {
+/// An abstract representation of an aligned address. This is designed to be an
+/// IR-level abstraction, carrying just the information necessary to perform IR
+/// operations on an address like loads and stores.  In particular, it doesn't
+/// carry C type information or allow the representation of things like
+/// bit-fields; clients working at that level should generally be using
+/// `LValue`.
+/// The pointer contained in this class is known to be unsigned.
+class RawAddress {
   llvm::PointerIntPair<llvm::Value *, 1, bool> PointerAndKnownNonNull;
   llvm::Type *ElementType;
   CharUnits Alignment;
 
 protected:
-  Address(std::nullptr_t) : ElementType(nullptr) {}
+  RawAddress(std::nullptr_t) : ElementType(nullptr) {}
 
 public:
-  Address(llvm::Value *Pointer, llvm::Type *ElementType, CharUnits Alignment,
-          KnownNonNull_t IsKnownNonNull = NotKnownNonNull)
+  RawAddress(llvm::Value *Pointer, llvm::Type *ElementType, CharUnits Alignment,
+             KnownNonNull_t IsKnownNonNull = NotKnownNonNull)
       : PointerAndKnownNonNull(Pointer, IsKnownNonNull),
         ElementType(ElementType), Alignment(Alignment) {
     assert(Pointer != nullptr && "Pointer cannot be null");
     assert(ElementType != nullptr && "Element type cannot be null");
   }
 
-  static Address invalid() { return Address(nullptr); }
+  inline RawAddress(Address Addr);
+
+  static RawAddress invalid() { return RawAddress(nullptr); }
   bool isValid() const {
     return PointerAndKnownNonNull.getPointer() != nullptr;
   }
@@ -80,6 +94,139 @@ class Address {
     return Alignment;
   }
 
+  /// Return address with different element type, but same pointer and
+  /// alignment.
+  RawAddress withElementType(llvm::Type *ElemTy) const {
+    return RawAddress(getPointer(), ElemTy, getAlignment(), isKnownNonNull());
+  }
+
+  KnownNonNull_t isKnownNonNull() const {
+    assert(isValid());
+    return (KnownNonNull_t)PointerAndKnownNonNull.getInt();
+  }
+};
+
+/// Like RawAddress, an abstract representation of an aligned address, but the
+/// pointer contained in this class is possibly signed.
+class Address {
+  friend class CGBuilderTy;
+
+  // The boolean flag indicates whether the pointer is known to be non-null.
+  llvm::PointerIntPair<llvm::Value *, 1, bool> Pointer;
+
+  /// The expected IR type of the pointer. When the address is a raw pointer,
+  /// this is currently redundant with the pointer's type, but for signed
+  /// pointers it is useful if the pointer has been offsetted or cast from the
+  /// original type. In the long run, when LLVM adopts opaque pointer types,
+  /// this should become the notional element type of the address.
+  ///
+  /// Carrying accurate element type information in Address makes it more
+  /// convenient to work with Address values and allows frontend assertions to
+  /// catch simple mistakes even after LLVM adopts opaque pointer types.
+  llvm::Type *ElementType = nullptr;
+
+  CharUnits Alignment;
+
+  /// Offset from the base pointer.
+  llvm::Value *Offset = nullptr;
+
+  llvm::Value *getRawPointerSlow(CodeGenFunction &CGF) const;
+
+protected:
+  Address(std::nullptr_t) : ElementType(nullptr) {}
+
+public:
+  Address(llvm::Value *pointer, llvm::Type *elementType, CharUnits alignment,
+          KnownNonNull_t IsKnownNonNull = NotKnownNonNull)
+      : Pointer(pointer, IsKnownNonNull), ElementType(elementType),
+        Alignment(alignment) {
+    assert(pointer != nullptr && "Pointer cannot be null");
+    assert(elementType != nullptr && "Element type cannot be null");
+    assert(!alignment.isZero() && "Alignment cannot be zero");
+  }
+
+  Address(llvm::Value *BasePtr, llvm::Type *ElementType, CharUnits Alignment,
+          llvm::Value *Offset, KnownNonNull_t IsKnownNonNull = NotKnownNonNull)
+      : Pointer(BasePtr, IsKnownNonNull), ElementType(ElementType),
+        Alignment(Alignment), Offset(Offset) {}
+
+  Address(RawAddress RawAddr)
+      : Pointer(RawAddr.isValid() ? RawAddr.getPointer() : nullptr),
+        ElementType(RawAddr.isValid() ? RawAddr.getElementType() : nullptr),
+        Alignment(RawAddr.isValid() ? RawAddr.getAlignment()
+                                    : CharUnits::Zero()) {}
+
+  static Address invalid() { return Address(nullptr); }
+  bool isValid() const { return Pointer.getPointer() != nullptr; }
+
+  /// This function is used in situations where the caller is doing some sort of
+  /// opaque "laundering" of the pointer.
+  void replaceBasePointer(llvm::Value *P) {
+    assert(isValid() && "pointer isn't valid");
+    assert(P->getType() == Pointer.getPointer()->getType() &&
+           "Pointer's type changed");
+    Pointer.setPointer(P);
+    assert(isValid() && "pointer is invalid after replacement");
+  }
+
+  CharUnits getAlignment() const { return Alignment; }
+
+  void setAlignment(CharUnits Value) { Alignment = Value; }
+
+  llvm::Value *getBasePointer() const {
+    assert(isValid() && "pointer isn't valid");
+    return Pointer.getPointer();
+  }
+
+  /// Return the type of the pointer value.
+  llvm::PointerType *getType() const {
+    return llvm::PointerType::get(
+        ElementType,
+        llvm::cast<llvm::PointerType>(Pointer.getPointer()->getType())
+            ->getAddressSpace());
+  }
+
+  /// Return the type of the values stored in this address.
+  llvm::Type *getElementType() const {
+    assert(isValid());
+    return ElementType;
+  }
+
+  /// Return the address space that this address resides in.
+  unsigned getAddressSpace() const { return getType()->getAddressSpace(); }
+
+  /// Return the IR name of the pointer value.
+  llvm::StringRef getName() const { return Pointer.getPointer()->getName(); }
+
+  // This function is called only in CGBuilderBaseTy::CreateElementBitCast.
+  void setElementType(llvm::Type *Ty) {
+    assert(hasOffset() &&
+           "this funcion shouldn't be called when there is no offset");
+    ElementType = Ty;
+  }
+
+  /// Whether the pointer is known not to be null.
+  KnownNonNull_t isKnownNonNull() const {
+    assert(isValid());
+    return (KnownNonNull_t)Pointer.getInt();
+  }
+
+  Address setKnownNonNull() {
+    assert(isValid());
+    Pointer.setInt(KnownNonNull);
+    return *this;
+  }
+
+  bool hasOffset() const { return Offset; }
+
+  llvm::Value *getOffset() const { return Offset; }
+
+  /// Return the pointer contained in this class after authenticating it and
+  /// adding offset to it if necessary.
+  llvm::Value *getRawPointer(CodeGenFunction &CGF) const {
+    return getBasePointer();
+  }
+
   /// Return address with different pointer, but same element type and
   /// alignment.
   Address withPointer(llvm::Value *NewPointer,
@@ -91,61 +238,59 @@ class Address {
   /// Return address with different alignment, but same pointer and element
   /// type.
   Address withAlignment(CharUnits NewAlignment) const {
-    return Address(getPointer(), getElementType(), NewAlignment,
+    return Address(Pointer.getPointer(), getElementType(), NewAlignment,
                    isKnownNonNull());
   }
 
   /// Return address with different element type, but same pointer and
   /// alignment.
   Address withElementType(llvm::Type *ElemTy) const {
-    return Address(getPointer(), ElemTy, getAlignment(), isKnownNonNull());
-  }
-
-  /// Whether the pointer is known not to be null.
-  KnownNonNull_t isKnownNonNull() const {
-    assert(isValid());
-    return (KnownNonNull_t)PointerAndKnownNonNull.getInt();
-  }
-
-  /// Set the non-null bit.
-  Address setKnownNonNull() {
-    assert(isValid());
-    PointerAndKnownNonNull.setInt(true);
-    return *this;
+    if (!hasOffset())
+      return Address(getBasePointer(), ElemTy, getAlignment(), nullptr,
+                     isKnownNonNull());
+    Address A(*this);
+    A.ElementType = ElemTy;
+    return A;
   }
 };
 
+inline RawAddress::RawAddress(Address Addr)
+    : PointerAndKnownNonNull(Addr.isValid() ? Addr.getBasePointer() : nullptr,
+                             Addr.isValid() ? Addr.isKnownNonNull()
+                                            : NotKnownNonNull),
+      ElementType(Addr.isValid() ? Addr.getElementType() : nullptr),
+      Alignment(Addr.isValid() ? Addr.getAlignment() : CharUnits::Zero()) {}
+
 /// A specialization of Address that requires the address to be an
 /// LLVM Constant.
-class ConstantAddress : public Address {
-  ConstantAddress(std::nullptr_t) : Address(nullptr) {}
+class ConstantAddress : public RawAddress {
+  ConstantAddress(std::nullptr_t) : RawAddress(nullptr) {}
 
 public:
   ConstantAddress(llvm::Constant *pointer, llvm::Type *elementType,
                   CharUnits alignment)
-      : Address(pointer, elementType, alignment) {}
+      : RawAddress(pointer, elementType, alignment) {}
 
   static ConstantAddress invalid() {
     return ConstantAddress(nullptr);
   }
 
   llvm::Constant *getPointer() const {
-    return llvm::cast<llvm::Constant>(Address::getPointer());
+    return llvm::cast<llvm::Constant>(RawAddress::getPointer());
   }
 
   ConstantAddress withElementType(llvm::Type *ElemTy) const {
     return ConstantAddress(getPointer(), ElemTy, getAlignment());
   }
 
-  static bool isaImpl(Address addr) {
+  static bool isaImpl(RawAddress addr) {
     return llvm::isa<llvm::Constant>(addr.getPointer());
   }
-  static ConstantAddress castImpl(Address addr) {
+  static ConstantAddress castImpl(RawAddress addr) {
     return ConstantAddress(llvm::cast<llvm::Constant>(addr.getPointer()),
                            addr.getElementType(), addr.getAlignment());
   }
 };
-
 }
 
 // Present a minimal LLVM-like casting interface.