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

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,60 @@
+//===- XtensaISelLowering.cpp - Xtensa DAG Lowering Implementation --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// 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 NULL;
----------------
arsenm wrote:

nullptr 

https://github.com/llvm/llvm-project/pull/78548