[Xtensa] Initial codegen support from IR (#78548)

This PR provides implementation of the basic codegen infra such as
TargetFrameLowering, MCInstLower,
AsmPrinter, RegisterInfo, InstructionInfo, TargetLowering,
SelectionDAGISel.

Migrated from https://reviews.llvm.org/D145658

Author: andreisfr

llvm/lib/Target/Xtensa/CMakeLists.txt

@@ -4,6 +4,7 @@ set(LLVM_TARGET_DEFINITIONS Xtensa.td)
 
 tablegen(LLVM XtensaGenAsmMatcher.inc -gen-asm-matcher)
 tablegen(LLVM XtensaGenAsmWriter.inc -gen-asm-writer)
+tablegen(LLVM XtensaGenDAGISel.inc -gen-dag-isel)
 tablegen(LLVM XtensaGenDisassemblerTables.inc -gen-disassembler)
 tablegen(LLVM XtensaGenInstrInfo.inc -gen-instr-info)
 tablegen(LLVM XtensaGenMCCodeEmitter.inc -gen-emitter)
@@ -13,13 +14,21 @@ tablegen(LLVM XtensaGenSubtargetInfo.inc -gen-subtarget)
 add_public_tablegen_target(XtensaCommonTableGen)
 
 add_llvm_target(XtensaCodeGen
+  XtensaAsmPrinter.cpp
+  XtensaFrameLowering.cpp
+  XtensaInstrInfo.cpp
+  XtensaISelDAGToDAG.cpp
+  XtensaISelLowering.cpp
+  XtensaRegisterInfo.cpp
+  XtensaSubtarget.cpp
   XtensaTargetMachine.cpp
 
   LINK_COMPONENTS
   AsmPrinter
   CodeGen
   Core
   MC
+  SelectionDAG
   Support
   Target
   XtensaDesc

llvm/lib/Target/Xtensa/Xtensa.h

@@ -0,0 +1,28 @@
+//===- Xtensa.h - Top-level interface for Xtensa representation -*- 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 contains the entry points for global functions defined in
+// the LLVM Xtensa back-end.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_XTENSA_XTENSA_H
+#define LLVM_LIB_TARGET_XTENSA_XTENSA_H
+
+#include "MCTargetDesc/XtensaMCTargetDesc.h"
+#include "llvm/PassRegistry.h"
+#include "llvm/Support/CodeGen.h"
+
+namespace llvm {
+class XtensaTargetMachine;
+class FunctionPass;
+
+FunctionPass *createXtensaISelDag(XtensaTargetMachine &TM,
+                                  CodeGenOptLevel OptLevel);
+} // namespace llvm
+#endif // LLVM_LIB_TARGET_XTENSA_XTENSA_H

llvm/lib/Target/Xtensa/XtensaAsmPrinter.cpp

@@ -0,0 +1,70 @@
+//===- XtensaAsmPrinter.cpp Xtensa LLVM Assembly Printer ------------------===//
+//
+// 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 contains a printer that converts from our internal representation
+// of machine-dependent LLVM code to GAS-format Xtensa assembly language.
+//
+//===----------------------------------------------------------------------===//
+
+#include "XtensaAsmPrinter.h"
+#include "TargetInfo/XtensaTargetInfo.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/CodeGen/MachineModuleInfoImpls.h"
+#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCSymbolELF.h"
+#include "llvm/MC/TargetRegistry.h"
+
+using namespace llvm;
+
+void XtensaAsmPrinter::emitInstruction(const MachineInstr *MI) {
+  MCInst LoweredMI;
+  lowerToMCInst(MI, LoweredMI);
+  EmitToStreamer(*OutStreamer, LoweredMI);
+}
+
+MCOperand XtensaAsmPrinter::lowerOperand(const MachineOperand &MO,
+                                         unsigned Offset) const {
+  MachineOperand::MachineOperandType MOTy = MO.getType();
+
+  switch (MOTy) {
+  case MachineOperand::MO_Register:
+    // Ignore all implicit register operands.
+    if (MO.isImplicit())
+      break;
+    return MCOperand::createReg(MO.getReg());
+  case MachineOperand::MO_Immediate:
+    return MCOperand::createImm(MO.getImm() + Offset);
+  case MachineOperand::MO_RegisterMask:
+    break;
+  default:
+    report_fatal_error("unknown operand type");
+  }
+
+  return MCOperand();
+}
+
+void XtensaAsmPrinter::lowerToMCInst(const MachineInstr *MI,
+                                     MCInst &OutMI) const {
+  OutMI.setOpcode(MI->getOpcode());
+
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    MCOperand MCOp = lowerOperand(MO);
+
+    if (MCOp.isValid())
+      OutMI.addOperand(MCOp);
+  }
+}
+
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeXtensaAsmPrinter() {
+  RegisterAsmPrinter<XtensaAsmPrinter> A(getTheXtensaTarget());
+}

llvm/lib/Target/Xtensa/XtensaAsmPrinter.h

@@ -0,0 +1,46 @@
+//===- XtensaAsmPrinter.h - Xtensa LLVM Assembly Printer --------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Xtensa Assembly printer class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_XTENSA_XTENSAASMPRINTER_H
+#define LLVM_LIB_TARGET_XTENSA_XTENSAASMPRINTER_H
+
+#include "XtensaTargetMachine.h"
+#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/Support/Compiler.h"
+
+namespace llvm {
+class MCStreamer;
+class MachineBasicBlock;
+class MachineInstr;
+class Module;
+class raw_ostream;
+
+class LLVM_LIBRARY_VISIBILITY XtensaAsmPrinter : public AsmPrinter {
+  const MCSubtargetInfo *STI;
+
+public:
+  explicit XtensaAsmPrinter(TargetMachine &TM,
+                            std::unique_ptr<MCStreamer> Streamer)
+      : AsmPrinter(TM, std::move(Streamer)), STI(TM.getMCSubtargetInfo()) {}
+
+  StringRef getPassName() const override { return "Xtensa Assembly Printer"; }
+  void emitInstruction(const MachineInstr *MI) override;
+
+  // Lower MachineInstr MI to MCInst OutMI.
+  void lowerToMCInst(const MachineInstr *MI, MCInst &OutMI) const;
+
+  // Return an MCOperand for MO.  Return an empty operand if MO is implicit.
+  MCOperand lowerOperand(const MachineOperand &MO, unsigned Offset = 0) const;
+};
+} // end namespace llvm
+
+#endif /* LLVM_LIB_TARGET_XTENSA_XTENSAASMPRINTER_H */

llvm/lib/Target/Xtensa/XtensaFrameLowering.cpp

@@ -0,0 +1,39 @@
+//===- XtensaFrameLowering.cpp - Xtensa Frame Information -----------------===//
+//
+// 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 contains the Xtensa implementation of TargetFrameLowering class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "XtensaFrameLowering.h"
+#include "XtensaInstrInfo.h"
+#include "XtensaSubtarget.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/IR/Function.h"
+
+using namespace llvm;
+
+XtensaFrameLowering::XtensaFrameLowering()
+    : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, Align(4), 0,
+                          Align(4)) {}
+
+bool XtensaFrameLowering::hasFP(const MachineFunction &MF) const {
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  return MF.getTarget().Options.DisableFramePointerElim(MF) ||
+         MFI.hasVarSizedObjects();
+}
+
+void XtensaFrameLowering::emitPrologue(MachineFunction &MF,
+                                       MachineBasicBlock &MBB) const {}
+
+void XtensaFrameLowering::emitEpilogue(MachineFunction &MF,
+                                       MachineBasicBlock &MBB) const {}

llvm/lib/Target/Xtensa/XtensaFrameLowering.h

@@ -0,0 +1,32 @@
+//===- XtensaFrameLowering.h - Define frame lowering for Xtensa --*- 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
+//
+//===-----------------------------------------------------------------------==//
+
+#ifndef LLVM_LIB_TARGET_XTENSA_XTENSAFRAMELOWERING_H
+#define LLVM_LIB_TARGET_XTENSA_XTENSAFRAMELOWERING_H
+
+#include "llvm/CodeGen/TargetFrameLowering.h"
+
+namespace llvm {
+class XtensaTargetMachine;
+class XtensaSubtarget;
+
+class XtensaFrameLowering : public TargetFrameLowering {
+public:
+  XtensaFrameLowering();
+
+  bool hasFP(const MachineFunction &MF) const override;
+
+  /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
+  /// the function.
+  void emitPrologue(MachineFunction &, MachineBasicBlock &) const override;
+  void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
+};
+
+} // namespace llvm
+
+#endif /* LLVM_LIB_TARGET_XTENSA_XTENSAFRAMELOWERING_H */

llvm/lib/Target/Xtensa/XtensaISelDAGToDAG.cpp

@@ -0,0 +1,79 @@
+//===- XtensaISelDAGToDAG.cpp - A dag to dag inst selector for Xtensa -----===//
+//
+// 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 an instruction selector for the Xtensa target.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Xtensa.h"
+#include "XtensaTargetMachine.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/SelectionDAGISel.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "xtensa-isel"
+
+namespace {
+
+class XtensaDAGToDAGISel : public SelectionDAGISel {
+public:
+  static char ID;
+
+  XtensaDAGToDAGISel(XtensaTargetMachine &TM, CodeGenOptLevel OptLevel)
+      : SelectionDAGISel(ID, TM, OptLevel) {}
+
+  StringRef getPassName() const override {
+    return "Xtensa DAG->DAG Pattern Instruction Selection";
+  }
+
+  void Select(SDNode *Node) override;
+
+  bool selectMemRegAddr(SDValue Addr, SDValue &Base, SDValue &Offset,
+                        int Scale) {
+    report_fatal_error("MemReg address is not implemented yet");
+  }
+
+  bool selectMemRegAddrISH1(SDValue Addr, SDValue &Base, SDValue &Offset) {
+    return selectMemRegAddr(Addr, Base, Offset, 1);
+  }
+
+  bool selectMemRegAddrISH2(SDValue Addr, SDValue &Base, SDValue &Offset) {
+    return selectMemRegAddr(Addr, Base, Offset, 2);
+  }
+
+  bool selectMemRegAddrISH4(SDValue Addr, SDValue &Base, SDValue &Offset) {
+    return selectMemRegAddr(Addr, Base, Offset, 4);
+  }
+
+// Include the pieces autogenerated from the target description.
+#include "XtensaGenDAGISel.inc"
+}; // namespace
+} // end anonymous namespace
+
+char XtensaDAGToDAGISel::ID = 0;
+
+FunctionPass *llvm::createXtensaISelDag(XtensaTargetMachine &TM,
+                                        CodeGenOptLevel OptLevel) {
+  return new XtensaDAGToDAGISel(TM, OptLevel);
+}
+
+void XtensaDAGToDAGISel::Select(SDNode *Node) {
+  SDLoc DL(Node);
+
+  // If we have a custom node, we already have selected!
+  if (Node->isMachineOpcode()) {
+    Node->setNodeId(-1);
+    return;
+  }
+
+  SelectCode(Node);
+}

llvm/lib/Target/Xtensa/XtensaISelLowering.cpp

@@ -0,0 +1,58 @@
+//===- XtensaISelLowering.cpp - Xtensa DAG Lowering Implementation --------===//
+//
+// 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 interfaces that Xtensa uses to lower LLVM code into a
+// selection DAG.
+//
+//===----------------------------------------------------------------------===//
+
+#include "XtensaISelLowering.h"
+#include "XtensaSubtarget.h"
+#include "XtensaTargetMachine.h"
+#include "llvm/CodeGen/CallingConvLower.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "xtensa-lower"
+
+XtensaTargetLowering::XtensaTargetLowering(const TargetMachine &TM,
+                                           const XtensaSubtarget &STI)
+    : TargetLowering(TM), Subtarget(STI) {
+  // Set up the register classes.
+  addRegisterClass(MVT::i32, &Xtensa::ARRegClass);
+
+  // Set up special registers.
+  setStackPointerRegisterToSaveRestore(Xtensa::SP);
+
+  setSchedulingPreference(Sched::RegPressure);
+
+  setMinFunctionAlignment(Align(4));
+
+  // Compute derived properties from the register classes
+  computeRegisterProperties(STI.getRegisterInfo());
+}
+
+SDValue XtensaTargetLowering::LowerOperation(SDValue Op,
+                                             SelectionDAG &DAG) const {
+  switch (Op.getOpcode()) {
+  default:
+    report_fatal_error("Unexpected node to lower");
+  }
+}
+
+const char *XtensaTargetLowering::getTargetNodeName(unsigned Opcode) const {
+  return nullptr;
+}