[CodeGen] Migrate away from PointerUnion::{is,get} (NFC) (#118600)

Note that PointerUnion::{is,get} have been soft deprecated in
PointerUnion.h:

  // FIXME: Replace the uses of is(), get() and dyn_cast() with
  //        isa<T>, cast<T> and the llvm::dyn_cast<T>

I'm not touching PointerUnion::dyn_cast for now because it's a bit
complicated; we could blindly migrate it to dyn_cast_if_present, but
we should probably use dyn_cast when the operand is known to be
non-null.

Author: kazutakahirata

clang/lib/CodeGen/CGCall.cpp

@@ -4529,7 +4529,7 @@ void CodeGenFunction::EmitCallArgs(
       ArgTypes.assign(MD->param_type_begin() + ParamsToSkip,
                       MD->param_type_end());
     } else {
-      const auto *FPT = Prototype.P.get<const FunctionProtoType *>();
+      const auto *FPT = cast<const FunctionProtoType *>(Prototype.P);
       IsVariadic = FPT->isVariadic();
       ExplicitCC = FPT->getExtInfo().getCC();
       ArgTypes.assign(FPT->param_type_begin() + ParamsToSkip,

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -7770,7 +7770,7 @@ class MappableExprsHandler {
       if (const auto *Base = Data.dyn_cast<const CXXRecordDecl *>())
         getPlainLayout(Base, Layout, /*AsBase=*/true);
       else
-        Layout.push_back(Data.get<const FieldDecl *>());
+        Layout.push_back(cast<const FieldDecl *>(Data));
     }
   }
 
@@ -8333,9 +8333,9 @@ class MappableExprsHandler {
       MapCombinedInfoTy &CombinedInfo, llvm::OpenMPIRBuilder &OMPBuilder,
       const llvm::DenseSet<CanonicalDeclPtr<const Decl>> &SkipVarSet =
           llvm::DenseSet<CanonicalDeclPtr<const Decl>>()) const {
-    assert(CurDir.is<const OMPExecutableDirective *>() &&
+    assert(isa<const OMPExecutableDirective *>(CurDir) &&
            "Expect a executable directive");
-    const auto *CurExecDir = CurDir.get<const OMPExecutableDirective *>();
+    const auto *CurExecDir = cast<const OMPExecutableDirective *>(CurDir);
     generateAllInfoForClauses(CurExecDir->clauses(), CombinedInfo, OMPBuilder,
                               SkipVarSet);
   }
@@ -8345,9 +8345,9 @@ class MappableExprsHandler {
   /// in \a CombinedInfo).
   void generateAllInfoForMapper(MapCombinedInfoTy &CombinedInfo,
                                 llvm::OpenMPIRBuilder &OMPBuilder) const {
-    assert(CurDir.is<const OMPDeclareMapperDecl *>() &&
+    assert(isa<const OMPDeclareMapperDecl *>(CurDir) &&
            "Expect a declare mapper directive");
-    const auto *CurMapperDir = CurDir.get<const OMPDeclareMapperDecl *>();
+    const auto *CurMapperDir = cast<const OMPDeclareMapperDecl *>(CurDir);
     generateAllInfoForClauses(CurMapperDir->clauses(), CombinedInfo,
                               OMPBuilder);
   }
@@ -8519,9 +8519,9 @@ class MappableExprsHandler {
         DeclComponentLists.emplace_back(MCL, OMPC_MAP_tofrom, Unknown,
                                         /*IsImpicit = */ true, nullptr,
                                         nullptr);
-    assert(CurDir.is<const OMPExecutableDirective *>() &&
+    assert(isa<const OMPExecutableDirective *>(CurDir) &&
            "Expect a executable directive");
-    const auto *CurExecDir = CurDir.get<const OMPExecutableDirective *>();
+    const auto *CurExecDir = cast<const OMPExecutableDirective *>(CurDir);
     bool HasMapBasePtr = false;
     bool HasMapArraySec = false;
     for (const auto *C : CurExecDir->getClausesOfKind<OMPMapClause>()) {

clang/lib/CodeGen/ConstantInitBuilder.cpp

@@ -20,10 +20,10 @@ using namespace CodeGen;
 
 llvm::Type *ConstantInitFuture::getType() const {
   assert(Data && "dereferencing null future");
-  if (Data.is<llvm::Constant*>()) {
-    return Data.get<llvm::Constant*>()->getType();
+  if (const auto *C = dyn_cast<llvm::Constant *>(Data)) {
+    return C->getType();
   } else {
-    return Data.get<ConstantInitBuilderBase*>()->Buffer[0]->getType();
+    return cast<ConstantInitBuilderBase *>(Data)->Buffer[0]->getType();
   }
 }
 
@@ -37,10 +37,10 @@ void ConstantInitFuture::abandon() {
 
 void ConstantInitFuture::installInGlobal(llvm::GlobalVariable *GV) {
   assert(Data && "installing null future");
-  if (Data.is<llvm::Constant*>()) {
-    GV->setInitializer(Data.get<llvm::Constant*>());
+  if (auto *C = dyn_cast<llvm::Constant *>(Data)) {
+    GV->setInitializer(C);
   } else {
-    auto &builder = *Data.get<ConstantInitBuilderBase*>();
+    auto &builder = *cast<ConstantInitBuilderBase *>(Data);
     assert(builder.Buffer.size() == 1);
     builder.setGlobalInitializer(GV, builder.Buffer[0]);
     builder.Buffer.clear();