[SandboxIR] Implement ConstantPointerNull (#107320)

This patch implements sandboxir::ConstantPointerNull mirroring
llvm::ConstantPointerNull.

Author: vporpo

llvm/include/llvm/SandboxIR/SandboxIR.h

@@ -121,6 +121,7 @@ class BasicBlock;
 class ConstantInt;
 class ConstantFP;
 class ConstantAggregateZero;
+class ConstantPointerNull;
 class Context;
 class Function;
 class Instruction;
@@ -318,6 +319,7 @@ class Value {
   friend class ConstantArray;         // For `Val`.
   friend class ConstantStruct;        // For `Val`.
   friend class ConstantAggregateZero; // For `Val`.
+  friend class ConstantPointerNull;   // For `Val`.
 
   /// All values point to the context.
   Context &Ctx;
@@ -987,6 +989,35 @@ class ConstantAggregateZero final : public Constant {
 #endif
 };
 
+// TODO: Inherit from ConstantData.
+class ConstantPointerNull final : public Constant {
+  ConstantPointerNull(llvm::ConstantPointerNull *C, Context &Ctx)
+      : Constant(ClassID::ConstantPointerNull, C, Ctx) {}
+  friend class Context; // For constructor.
+
+public:
+  static ConstantPointerNull *get(PointerType *Ty);
+
+  PointerType *getType() const;
+
+  /// For isa/dyn_cast.
+  static bool classof(const sandboxir::Value *From) {
+    return From->getSubclassID() == ClassID::ConstantPointerNull;
+  }
+  unsigned getUseOperandNo(const Use &Use) const final {
+    llvm_unreachable("ConstantPointerNull has no operands!");
+  }
+#ifndef NDEBUG
+  void verify() const override {
+    assert(isa<llvm::ConstantPointerNull>(Val) && "Expected a CPNull!");
+  }
+  void dumpOS(raw_ostream &OS) const override {
+    dumpCommonPrefix(OS);
+    dumpCommonSuffix(OS);
+  }
+#endif
+};
+
 /// Iterator for `Instruction`s in a `BasicBlock.
 /// \Returns an sandboxir::Instruction & when derereferenced.
 class BBIterator {

llvm/include/llvm/SandboxIR/SandboxIRValues.def

@@ -31,6 +31,7 @@ DEF_CONST(ConstantArray, ConstantArray)
 DEF_CONST(ConstantStruct, ConstantStruct)
 DEF_CONST(ConstantVector, ConstantVector)
 DEF_CONST(ConstantAggregateZero, ConstantAggregateZero)
+DEF_CONST(ConstantPointerNull, ConstantPointerNull)
 
 #ifndef DEF_INSTR
 #define DEF_INSTR(ID, OPCODE, CLASS)

llvm/lib/SandboxIR/SandboxIR.cpp

@@ -2426,6 +2426,17 @@ Constant *ConstantAggregateZero::getElementValue(unsigned Idx) const {
       cast<llvm::ConstantAggregateZero>(Val)->getElementValue(Idx)));
 }
 
+ConstantPointerNull *ConstantPointerNull::get(PointerType *Ty) {
+  auto *LLVMC =
+      llvm::ConstantPointerNull::get(cast<llvm::PointerType>(Ty->LLVMTy));
+  return cast<ConstantPointerNull>(Ty->getContext().getOrCreateConstant(LLVMC));
+}
+
+PointerType *ConstantPointerNull::getType() const {
+  return cast<PointerType>(
+      Ctx.getType(cast<llvm::ConstantPointerNull>(Val)->getType()));
+}
+
 FunctionType *Function::getFunctionType() const {
   return cast<FunctionType>(
       Ctx.getType(cast<llvm::Function>(Val)->getFunctionType()));
@@ -2535,6 +2546,10 @@ Value *Context::getOrCreateValueInternal(llvm::Value *LLVMV, llvm::User *U) {
       }
       return Ret;
     }
+    case llvm::Value::ConstantPointerNullVal:
+      It->second = std::unique_ptr<ConstantPointerNull>(
+          new ConstantPointerNull(cast<llvm::ConstantPointerNull>(C), *this));
+      return It->second.get();
     case llvm::Value::ConstantArrayVal:
       It->second = std::unique_ptr<ConstantArray>(
           new ConstantArray(cast<llvm::ConstantArray>(C), *this));

llvm/unittests/SandboxIR/SandboxIRTest.cpp

@@ -589,6 +589,33 @@ define void @foo(ptr %ptr, {i32, i8} %v1, <2 x i8> %v2) {
   EXPECT_EQ(NewVectorCAZ->getElementCount(), ElementCount::getFixed(4));
 }
 
+TEST_F(SandboxIRTest, ConstantPointerNull) {
+  parseIR(C, R"IR(
+define ptr @foo() {
+  ret ptr null
+}
+)IR");
+  Function &LLVMF = *M->getFunction("foo");
+  sandboxir::Context Ctx(C);
+
+  auto &F = *Ctx.createFunction(&LLVMF);
+  auto &BB = *F.begin();
+  auto It = BB.begin();
+  auto *Ret = cast<sandboxir::ReturnInst>(&*It++);
+  // Check classof() and creation.
+  auto *CPNull = cast<sandboxir::ConstantPointerNull>(Ret->getReturnValue());
+  // Check get().
+  auto *NewCPNull =
+      sandboxir::ConstantPointerNull::get(sandboxir::PointerType::get(Ctx, 0u));
+  EXPECT_EQ(NewCPNull, CPNull);
+  auto *NewCPNull2 =
+      sandboxir::ConstantPointerNull::get(sandboxir::PointerType::get(Ctx, 1u));
+  EXPECT_NE(NewCPNull2, CPNull);
+  // Check getType().
+  EXPECT_EQ(CPNull->getType(), sandboxir::PointerType::get(Ctx, 0u));
+  EXPECT_EQ(NewCPNull2->getType(), sandboxir::PointerType::get(Ctx, 1u));
+}
+
 TEST_F(SandboxIRTest, Use) {
   parseIR(C, R"IR(
 define i32 @foo(i32 %v0, i32 %v1) {