[DirectX] Add MC Register and Frame stubs

[beanz]

Summary

This patch adds no-op stubs overrides for the MCRegisterInfo and
MCFrameLowering for the DirectX/DXIL code generation path.

Since DXIL will not generate MCInstrs these stubs do nothing, but they
need to exist so that the MC layer can be used to emit DXContainer
objects.

[beanz]

Forgot the CMake lines to generate the tablegen headers.

[beanz]

Last update (I swear). Adding in the InstrInfo stub too because it is equivalently silly.

[python3kgae]

llvm/lib/Target/DirectX/MCTargetDesc/DirectXMCTargetDesc.h

18

DXIL registers?

[beanz]

Fixing copy-paste comment errors.

[beanz]

llvm/lib/Target/DirectX/MCTargetDesc/DirectXMCTargetDesc.h

18

Doh... clearly some copypasta here...

[python3kgae]

Do we need any test for this change?

[beanz]

In D127147#3561579, @python3kgae wrote:

Do we need any test for this change?

This is complicated... This particular patch is effectively NFC. Since there is no implementation to any of this code, it doesn't actually _do_anything (and really never will).

There are other patches in this stack (some not yet posted) which do have functionality, but they also aren't very testable because the MC-layer (and particularly the object streamer infrastructure) isn't architected to be as flexible for testing as other parts of LLVM.

Before any of this code becomes live a lot of other code all needs to fall into place. I'm working on getting the full patch set posted.

[kuhar]

llvm/lib/Target/DirectX/DirectXFrameLowering.h

30–35

I'm afraid these can lead to unused function argument warnings. Can we remove argument names to silence such warnings?

llvm/lib/Target/DirectX/DirectXInstrInfo.h

26 ↗

(On Diff #434609)

AFAIK at least one virtual function should be defined in a C++ file: https://llvm.org/docs/CodingStandards.html#provide-a-virtual-method-anchor-for-classes-in-headers

llvm/lib/Target/DirectX/DirectXRegisterInfo.h

25

Also here

[beanz]

llvm/lib/Target/DirectX/DirectXFrameLowering.h

30–35

I'm happy to make this change (I prefer it myself), but I do want to point out that LLVM is nowhere near clean for -Wunused-parameter, and it isn't a warning we generally support.

[beanz]

Updates based on PR feedback.

[kuhar]

LGTM but please get a second approval before submitting.

llvm/lib/Target/DirectX/DirectXFrameLowering.h

30–35

Ack, so it must have been llvm headers being pulled into other projects that generated such warnings for me in the past. Feels free to disregard this in other reviews that I sent as well.

[beanz]

Looping in a few extra reviewers for some more eyes.

[rengolin]

This looks fine to me. I don't see how this can be tested and if it never will have functionality in the future, there's not point in even trying.

[MaskRay]

llvm/lib/Target/DirectX/DXILStubs.td

9

unneeded wrap

11

delete blank line

llvm/lib/Target/DirectX/CMakeLists.txt

 add_llvm_component_group(DirectX)
 
 set(LLVM_TARGET_DEFINITIONS DirectX.td)
 
 tablegen(LLVM DirectXGenSubtargetInfo.inc -gen-subtarget)
+tablegen(LLVM DirectXGenInstrInfo.inc -gen-instr-info)
+tablegen(LLVM DirectXGenRegisterInfo.inc -gen-register-info)
 
 add_public_tablegen_target(DirectXCommonTableGen)
 
 add_llvm_target(DirectXCodeGen
+  DirectXRegisterInfo.cpp
   DirectXSubtarget.cpp
   DirectXTargetMachine.cpp
   DXILOpLowering.cpp
   DXILPointerType.cpp
   DXILPrepare.cpp
   DXILTranslateMetadata.cpp
   PointerTypeAnalysis.cpp
 

llvm/lib/Target/DirectX/DXILStubs.td

+// DXIL doesn't actually use registers, but this gets the boilerplate code
+// generated through tablegen.
+let Namespace = "DXIL" in {
+def DXIL : Register<"DXIL">;
+def DXILClass : RegisterClass<"DXIL", [i32], 32, (add DXIL)>;
+}
+
+class DXILInst
+  : Instruction {
+
+  let Namespace = "DXIL";
+  let DecoderNamespace = "DXIL";
+
+  dag OutOperandList = (outs);
+  dag InOperandList =  (ins);
+  let AsmString = "dummy";
+  let Pattern = [];
+}
+
+def DummyInst : DXILInst;

llvm/lib/Target/DirectX/DirectX.td

 ///
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//
 // Target-independent interfaces which we are implementing
 //===----------------------------------------------------------------------===//
 
 include "llvm/Target/Target.td"
+include "DXILStubs.td"
 
 //===----------------------------------------------------------------------===//
 // DirectX Subtarget features.
 //===----------------------------------------------------------------------===//
 
 def DirectXInstrInfo : InstrInfo;
 
 //===----------------------------------------------------------------------===//

llvm/lib/Target/DirectX/DirectXFrameLowering.h

+//===-- DirectXFrameLowering.h - Frame lowering for DirectX --*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This class implements DirectX-specific bits of TargetFrameLowering class.
+// This is just a stub because the current DXIL backend does not actually lower
+// through the MC layer.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DIRECTX_DIRECTXFRAMELOWERING_H
+#define LLVM_DIRECTX_DIRECTXFRAMELOWERING_H
+
+#include "llvm/CodeGen/TargetFrameLowering.h"
+#include "llvm/Support/Alignment.h"
+
+namespace llvm {
+class DirectXSubtarget;
+
+class DirectXFrameLowering : public TargetFrameLowering {
+public:
+  explicit DirectXFrameLowering(const DirectXSubtarget &STI)
+      : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, Align(8), 0) {}
+
+  void emitPrologue(MachineFunction &MF,
+                    MachineBasicBlock &MBB) const override {}
+  void emitEpilogue(MachineFunction &MF,
+                    MachineBasicBlock &MBB) const override {}
+
+  bool hasFP(const MachineFunction &MF) const override { return false; }
+};
+} // namespace llvm
+#endif // LLVM_DIRECTX_DIRECTXFRAMELOWERING_H

llvm/lib/Target/DirectX/DirectXRegisterInfo.h

+//===-- DirectXRegisterInfo.h - Define RegisterInfo for DirectX -*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the DirectX specific subclass of TargetRegisterInfo.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DIRECTX_DXILREGISTERINFO_H
+#define LLVM_DIRECTX_DXILREGISTERINFO_H
+
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+
+#define GET_REGINFO_HEADER
+#include "DirectXGenRegisterInfo.inc"
+
+namespace llvm {
+struct DirectXRegisterInfo : public DirectXGenRegisterInfo {
+  DirectXRegisterInfo() : DirectXGenRegisterInfo(0) {}
+  ~DirectXRegisterInfo() override = default;
+};
+} // namespace llvm
+
+#endif // LLVM_DIRECTX_DXILREGISTERINFO_H

llvm/lib/Target/DirectX/DirectXRegisterInfo.cpp

+//===-- DirectXRegisterInfo.cpp - RegisterInfo for DirectX -*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the DirectX specific subclass of TargetRegisterInfo.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DirectXRegisterInfo.h"
+#include "DirectXFrameLowering.h"
+#include "MCTargetDesc/DirectXMCTargetDesc.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+
+#define GET_REGINFO_TARGET_DESC
+#include "DirectXGenRegisterInfo.inc"

llvm/lib/Target/DirectX/MCTargetDesc/DirectXMCTargetDesc.h

+//===- DirectXMCTargetDesc.h - DirectX Target Interface ---------*- 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains DirectX target interface.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DIRECTX_DIRECTXMCTARGETDESC_H
+#define LLVM_DIRECTX_DIRECTXMCTARGETDESC_H
+
+// Defines symbolic names for AArch64 registers.  This defines a mapping from
+// register name to register number.
+//
+#define GET_REGINFO_ENUM
+#include "DirectXGenRegisterInfo.inc"
+
+// Defines symbolic names for the AArch64 instructions.
+//
+#define GET_INSTRINFO_ENUM
+#define GET_INSTRINFO_MC_HELPER_DECLS
+#include "DirectXGenInstrInfo.inc"
+
+#define GET_SUBTARGETINFO_ENUM
+#include "DirectXGenSubtargetInfo.inc"
+
+#endif // LLVM_DIRECTX_DIRECTXMCTARGETDESC_H