[CodeGen][RISCV] Add helper class for emitting CFI instructions into MIR (#135845)

PR: #135845

Author: s-barannikov

llvm/include/llvm/CodeGen/CFIInstBuilder.h

@@ -0,0 +1,88 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_CODEGEN_CFIINSTBUILDER_H
+#define LLVM_CODEGEN_CFIINSTBUILDER_H
+
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/MC/MCDwarf.h"
+
+namespace llvm {
+
+/// Helper class for creating CFI instructions and inserting them into MIR.
+class CFIInstBuilder {
+  MachineFunction &MF;
+  MachineBasicBlock &MBB;
+  MachineBasicBlock::iterator InsertPt;
+
+  /// MIFlag to set on a MachineInstr. Typically, FrameSetup or FrameDestroy.
+  MachineInstr::MIFlag MIFlag;
+
+  /// Selects DWARF register numbering: debug or exception handling. Should be
+  /// consistent with the choice of the ELF section (.debug_frame or .eh_frame)
+  /// where CFI will be encoded.
+  bool IsEH;
+
+  // Cache frequently used variables.
+  const TargetRegisterInfo &TRI;
+  const MCInstrDesc &CFIID;
+  const MIMetadata MIMD; // Default-initialized, no debug location desired.
+
+public:
+  CFIInstBuilder(MachineBasicBlock &MBB, MachineBasicBlock::iterator InsertPt,
+                 MachineInstr::MIFlag MIFlag, bool IsEH = true)
+      : MF(*MBB.getParent()), MBB(MBB), MIFlag(MIFlag), IsEH(IsEH),
+        TRI(*MF.getSubtarget().getRegisterInfo()),
+        CFIID(MF.getSubtarget().getInstrInfo()->get(
+            TargetOpcode::CFI_INSTRUCTION)) {
+    setInsertPoint(InsertPt);
+  }
+
+  void setInsertPoint(MachineBasicBlock::iterator IP) { InsertPt = IP; }
+
+  void insertCFIInst(const MCCFIInstruction &CFIInst) const {
+    BuildMI(MBB, InsertPt, MIMD, CFIID)
+        .addCFIIndex(MF.addFrameInst(CFIInst))
+        .setMIFlag(MIFlag);
+  }
+
+  void buildDefCFA(MCRegister Reg, int64_t Offset) const {
+    insertCFIInst(MCCFIInstruction::cfiDefCfa(
+        nullptr, TRI.getDwarfRegNum(Reg, IsEH), Offset));
+  }
+
+  void buildDefCFARegister(MCRegister Reg) const {
+    insertCFIInst(MCCFIInstruction::createDefCfaRegister(
+        nullptr, TRI.getDwarfRegNum(Reg, IsEH)));
+  }
+
+  void buildDefCFAOffset(int64_t Offset) const {
+    insertCFIInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, Offset));
+  }
+
+  void buildOffset(MCRegister Reg, int64_t Offset) const {
+    insertCFIInst(MCCFIInstruction::createOffset(
+        nullptr, TRI.getDwarfRegNum(Reg, IsEH), Offset));
+  }
+
+  void buildRestore(MCRegister Reg) const {
+    insertCFIInst(MCCFIInstruction::createRestore(
+        nullptr, TRI.getDwarfRegNum(Reg, IsEH)));
+  }
+
+  void buildEscape(StringRef Bytes, StringRef Comment = "") const {
+    insertCFIInst(
+        MCCFIInstruction::createEscape(nullptr, Bytes, SMLoc(), Comment));
+  }
+};
+
+} // namespace llvm
+
+#endif // LLVM_CODEGEN_CFIINSTBUILDER_H