[NFC] Refactor dxil metadata code

[beanz]

Summary

DXIL relies on a whole bunch of IR metadata constructs being populated
in the right shape. Rather than just hard coding or using complicated
arrangements of constant data strings, let's make first-class objects
that reprensent the metadata and manage reading and writing the
metadata from the module.

[python3kgae]

llvm/lib/Target/DirectX/DXILMetadata.h

23

Maybe ValidatorVersionMD?

26

Shall we add something like VersionTuple getValidationVersion() to read the version?

[beanz]

llvm/lib/Target/DirectX/DXILMetadata.h

23

I like that name better, will update.

26

I don't want to add an API that we don't currently have a use for. I don't see any reason we couldn't add this in the future, but right now we don't need it.

[beanz]

Renaming ValidationVersionMD -> ValidatorVersionMD

llvm/lib/Target/DirectX/CMakeLists.txt

 add_public_tablegen_target(DirectXCommonTableGen)
 
 add_llvm_target(DirectXCodeGen
   DirectXAsmPrinter.cpp
   DirectXInstrInfo.cpp
   DirectXRegisterInfo.cpp
   DirectXSubtarget.cpp
   DirectXTargetMachine.cpp
+  DXILMetadata.cpp
   DXILOpBuilder.cpp
   DXILOpLowering.cpp
   DXILPrepare.cpp
   DXILTranslateMetadata.cpp
   PointerTypeAnalysis.cpp
 
   LINK_COMPONENTS
   AsmPrinter

llvm/lib/Target/DirectX/DXILMetadata.h

+//===- DXILMetadata.h - DXIL Metadata helper objects ----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file This file contains helper objects for working with DXIL metadata.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TARGET_DIRECTX_DXILMETADATA_H
+#define LLVM_TARGET_DIRECTX_DXILMETADATA_H
+
+namespace llvm {
+class Module;
+class NamedMDNode;
+class VersionTuple;
+namespace dxil {
+
+class ValidatorVersionMD {
+  NamedMDNode *Entry;
+
+public:
+  ValidatorVersionMD(Module &M);
+
+  void update(VersionTuple ValidatorVer);
+
+  bool isEmpty();
+};
+
+} // namespace dxil
+} // namespace llvm
+
+#endif // LLVM_TARGET_DIRECTX_DXILMETADATA_H

llvm/lib/Target/DirectX/DXILMetadata.cpp

+//===- DXILMetadata.cpp - DXIL Metadata helper objects --------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file This file contains helper objects for working with DXIL metadata.
+///
+//===----------------------------------------------------------------------===//
+
+#include "DXILMetadata.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/VersionTuple.h"
+
+using namespace llvm;
+using namespace llvm::dxil;
+
+ValidatorVersionMD::ValidatorVersionMD(Module &M)
+    : Entry(M.getOrInsertNamedMetadata("dx.valver")) {}
+
+void ValidatorVersionMD::update(VersionTuple ValidatorVer) {
+  auto &Ctx = Entry->getParent()->getContext();
+  IRBuilder<> B(Ctx);
+  Metadata *MDVals[2];
+
+  MDVals[0] = ConstantAsMetadata::get(B.getInt32(ValidatorVer.getMajor()));
+  MDVals[1] =
+      ConstantAsMetadata::get(B.getInt32(ValidatorVer.getMinor().value_or(0)));
+
+  if (isEmpty())
+    Entry->addOperand(MDNode::get(Ctx, MDVals));
+  else
+    Entry->setOperand(0, MDNode::get(Ctx, MDVals));
+}
+
+bool ValidatorVersionMD::isEmpty() { return Entry->getNumOperands() == 0; }

llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp

 //===- DXILTranslateMetadata.cpp - Pass to emit DXIL metadata ---*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 ///
 //===----------------------------------------------------------------------===//
 
+#include "DXILMetadata.h"
 #include "DirectX.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Pass.h"
 
 using namespace llvm;
 
-static uint32_t ConstMDToUint32(const MDOperand &MDO) {
-  ConstantInt *pConst = mdconst::extract<ConstantInt>(MDO);
-  return (uint32_t)pConst->getZExtValue();
-}
-
-static ConstantAsMetadata *Uint32ToConstMD(unsigned v, LLVMContext &Ctx) {
-  return ConstantAsMetadata::get(
-      Constant::getIntegerValue(IntegerType::get(Ctx, 32), APInt(32, v)));
-}
-
-constexpr StringLiteral ValVerKey = "dx.valver";
-constexpr unsigned DXILVersionNumFields = 2;
-
-static void emitDXILValidatorVersion(Module &M, VersionTuple &ValidatorVer) {
-  NamedMDNode *DXILValidatorVersionMD = M.getNamedMetadata(ValVerKey);
-
-  // Allow re-writing the validator version, since this can be changed at
-  // later points.
-  if (DXILValidatorVersionMD)
-    M.eraseNamedMetadata(DXILValidatorVersionMD);
-
-  DXILValidatorVersionMD = M.getOrInsertNamedMetadata(ValVerKey);
-
-  auto &Ctx = M.getContext();
-  Metadata *MDVals[DXILVersionNumFields];
-  MDVals[0] = Uint32ToConstMD(ValidatorVer.getMajor(), Ctx);
-  MDVals[1] = Uint32ToConstMD(ValidatorVer.getMinor().value_or(0), Ctx);
-
-  DXILValidatorVersionMD->addOperand(MDNode::get(Ctx, MDVals));
-}
-
-static VersionTuple loadDXILValidatorVersion(MDNode *ValVerMD) {
-  if (ValVerMD->getNumOperands() != DXILVersionNumFields)
-    return VersionTuple();
-
-  unsigned Major = ConstMDToUint32(ValVerMD->getOperand(0));
-  unsigned Minor = ConstMDToUint32(ValVerMD->getOperand(1));
-  return VersionTuple(Major, Minor);
-}
-
 namespace {
 class DXILTranslateMetadata : public ModulePass {
 public:
   static char ID; // Pass identification, replacement for typeid
-  explicit DXILTranslateMetadata() : ModulePass(ID), ValidatorVer(1, 0) {}
+  explicit DXILTranslateMetadata() : ModulePass(ID) {}
 
   StringRef getPassName() const override { return "DXIL Metadata Emit"; }
 
   bool runOnModule(Module &M) override;
-
-private:
-  VersionTuple ValidatorVer;
 };
 
 } // namespace
 
 bool DXILTranslateMetadata::runOnModule(Module &M) {
-  if (NamedMDNode *ValVerMD = M.getNamedMetadata(ValVerKey)) {
-    VersionTuple ValVer = loadDXILValidatorVersion(ValVerMD->getOperand(0));
-    if (!ValVer.empty())
-      ValidatorVer = ValVer;
-  }
-  emitDXILValidatorVersion(M, ValidatorVer);
+
+  dxil::ValidatorVersionMD ValVerMD(M);
+  if (ValVerMD.isEmpty())
+    ValVerMD.update(VersionTuple(1, 0));
   return false;
 }
 
 char DXILTranslateMetadata::ID = 0;
 
 ModulePass *llvm::createDXILTranslateMetadataPass() {
   return new DXILTranslateMetadata();
 }
 
 INITIALIZE_PASS(DXILTranslateMetadata, "dxil-metadata-emit",
                 "DXIL Metadata Emit", false, false)