[IR] Make UnaryInstruction::classof recognize FreezeInst. (#107944)

Author: slackito

llvm/include/llvm/IR/InstrTypes.h

@@ -80,11 +80,11 @@ class UnaryInstruction : public Instruction {
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Instruction *I) {
-    return I->isUnaryOp() ||
-           I->getOpcode() == Instruction::Alloca ||
+    return I->isUnaryOp() || I->getOpcode() == Instruction::Alloca ||
            I->getOpcode() == Instruction::Load ||
            I->getOpcode() == Instruction::VAArg ||
            I->getOpcode() == Instruction::ExtractValue ||
+           I->getOpcode() == Instruction::Freeze ||
            (I->getOpcode() >= CastOpsBegin && I->getOpcode() < CastOpsEnd);
   }
   static bool classof(const Value *V) {

llvm/unittests/IR/InstructionsTest.cpp

@@ -1733,6 +1733,20 @@ TEST(InstructionsTest, BranchWeightOverflow) {
   ASSERT_EQ(ProfWeight, UINT32_MAX);
 }
 
+TEST(InstructionsTest, FreezeInst) {
+  LLVMContext C;
+  std::unique_ptr<Module> M = parseIR(C,
+                                      R"(
+      define void @foo(i8 %arg) {
+        freeze i8 %arg
+        ret void
+  }
+  )");
+  ASSERT_TRUE(M);
+  Value *FI = &M->getFunction("foo")->getEntryBlock().front();
+  EXPECT_TRUE(isa<UnaryInstruction>(FI));
+}
+
 TEST(InstructionsTest, AllocaInst) {
   LLVMContext Ctx;
   std::unique_ptr<Module> M = parseIR(Ctx, R"(