[AVR] Add the machine code disassembler

This adds a super basic implementation of a machine code disassembler.

It doesn't support any operands with custom encoding.

llvm-svn: 284930

1 files changed, 160 insertions, 0 deletions

diff --git a/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp b/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
new file mode 100644
index 00000000000..ae87d64dced
--- /dev/null
+++ b/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
@@ -0,0 +1,160 @@
+//===- AVRDisassembler.cpp - Disassembler for AVR ---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is part of the AVR Disassembler.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AVR.h"
+#include "AVRRegisterInfo.h"
+#include "AVRSubtarget.h"
+#include "MCTargetDesc/AVRMCTargetDesc.h"
+
+#include "llvm/MC/MCDisassembler/MCDisassembler.h"
+#include "llvm/MC/MCFixedLenDisassembler.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/Support/TargetRegistry.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "avr-disassembler"
+
+typedef MCDisassembler::DecodeStatus DecodeStatus;
+
+namespace {
+
+/// A disassembler class for AVR.
+class AVRDisassembler : public MCDisassembler {
+public:
+  AVRDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
+      : MCDisassembler(STI, Ctx) {}
+  virtual ~AVRDisassembler() {}
+
+  DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
+                              ArrayRef<uint8_t> Bytes, uint64_t Address,
+                              raw_ostream &VStream,
+                              raw_ostream &CStream) const override;
+};
+}
+
+namespace llvm {
+extern Target TheAVRTarget;
+}
+
+static MCDisassembler *createAVRDisassembler(const Target &T,
+                                             const MCSubtargetInfo &STI,
+                                             MCContext &Ctx) {
+  return new AVRDisassembler(STI, Ctx);
+}
+
+
+extern "C" void LLVMInitializeAVRDisassembler() {
+  // Register the disassembler.
+  TargetRegistry::RegisterMCDisassembler(TheAVRTarget,
+                                         createAVRDisassembler);
+}
+
+static DecodeStatus DecodeGPR8RegisterClass(MCInst &Inst, unsigned RegNo,
+                                            uint64_t Address, const void *Decoder) {
+  return MCDisassembler::Success;
+}
+
+static DecodeStatus DecodeLD8RegisterClass(MCInst &Inst, unsigned RegNo,
+                                           uint64_t Address, const void *Decoder) {
+  return MCDisassembler::Success;
+}
+
+static DecodeStatus DecodePTRREGSRegisterClass(MCInst &Inst, unsigned RegNo,
+                                               uint64_t Address, const void *Decoder) {
+  return MCDisassembler::Success;
+}
+
+#include "AVRGenDisassemblerTables.inc"
+
+static DecodeStatus readInstruction16(ArrayRef<uint8_t> Bytes, uint64_t Address,
+                                      uint64_t &Size, uint32_t &Insn) {
+  if (Bytes.size() < 2) {
+    Size = 0;
+    return MCDisassembler::Fail;
+  }
+
+  Size = 2;
+  Insn = (Bytes[0] << 0) | (Bytes[1] << 8);
+
+  return MCDisassembler::Success;
+}
+
+static DecodeStatus readInstruction32(ArrayRef<uint8_t> Bytes, uint64_t Address,
+                                      uint64_t &Size, uint32_t &Insn) {
+
+  if (Bytes.size() < 4) {
+    Size = 0;
+    return MCDisassembler::Fail;
+  }
+
+  Size = 4;
+  Insn = (Bytes[0] << 0) | (Bytes[1] << 8) | (Bytes[2] << 16) | (Bytes[3] << 24);
+
+  return MCDisassembler::Success;
+}
+
+static const uint8_t *getDecoderTable(uint64_t Size) {
+
+  switch (Size) {
+    case 2: return DecoderTable16;
+    case 4: return DecoderTable32;
+    default: llvm_unreachable("instructions must be 16 or 32-bits");
+  }
+}
+
+DecodeStatus AVRDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
+                                             ArrayRef<uint8_t> Bytes,
+                                             uint64_t Address,
+                                             raw_ostream &VStream,
+                                             raw_ostream &CStream) const {
+  uint32_t Insn;
+
+  DecodeStatus Result;
+
+  // Try decode a 16-bit instruction.
+  {
+    Result = readInstruction16(Bytes, Address, Size, Insn);
+
+    if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
+
+    // Try to auto-decode a 16-bit instruction.
+    Result = decodeInstruction(getDecoderTable(Size), Instr,
+                               Insn, Address, this, STI);
+
+    if (Result != MCDisassembler::Fail)
+      return Result;
+  }
+
+  // Try decode a 32-bit instruction.
+  {
+    Result = readInstruction32(Bytes, Address, Size, Insn);
+
+    if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
+
+    Result = decodeInstruction(getDecoderTable(Size), Instr, Insn,
+                               Address, this, STI);
+
+    if (Result != MCDisassembler::Fail) {
+      return Result;
+    }
+
+    return MCDisassembler::Fail;
+  }
+}
+
+typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address,
+                                   const void *Decoder);
+