llvm-6502/lib/Target/X86/InstPrinter/X86InstComments.cpp

//===-- X86InstComments.cpp - Generate verbose-asm comments for instrs ----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines functionality used to emit comments about X86 instructions to
// an output stream for -fverbose-asm.
//
//===----------------------------------------------------------------------===//

#include "X86InstComments.h"
#include "MCTargetDesc/X86MCTargetDesc.h"
#include "Utils/X86ShuffleDecode.h"
#include "llvm/MC/MCInst.h"
#include "llvm/CodeGen/MachineValueType.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

//===----------------------------------------------------------------------===//
// Top Level Entrypoint
//===----------------------------------------------------------------------===//

/// EmitAnyX86InstComments - This function decodes x86 instructions and prints
/// newline terminated strings to the specified string if desired.  This
/// information is shown in disassembly dumps when verbose assembly is enabled.
bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
                                  const char *(*getRegName)(unsigned)) {
  // If this is a shuffle operation, the switch should fill in this state.
  SmallVector<int, 8> ShuffleMask;
  const char *DestName = nullptr, *Src1Name = nullptr, *Src2Name = nullptr;

  switch (MI->getOpcode()) {
  default:
    // Not an instruction for which we can decode comments.
    return false;

  case X86::BLENDPDrri:
  case X86::VBLENDPDrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::BLENDPDrmi:
  case X86::VBLENDPDrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v2f64,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VBLENDPDYrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VBLENDPDYrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v4f64,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::BLENDPSrri:
  case X86::VBLENDPSrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::BLENDPSrmi:
  case X86::VBLENDPSrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v4f32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VBLENDPSYrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VBLENDPSYrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v8f32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::PBLENDWrri:
  case X86::VPBLENDWrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PBLENDWrmi:
  case X86::VPBLENDWrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v8i16,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPBLENDWYrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPBLENDWYrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v16i16,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::VPBLENDDrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPBLENDDrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v4i32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::VPBLENDDYrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPBLENDDYrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeBLENDMask(MVT::v8i32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::INSERTPSrr:
  case X86::VINSERTPSrr:
    DestName = getRegName(MI->getOperand(0).getReg());
    Src1Name = getRegName(MI->getOperand(1).getReg());
    Src2Name = getRegName(MI->getOperand(2).getReg());
    if(MI->getOperand(3).isImm())
      DecodeINSERTPSMask(MI->getOperand(3).getImm(), ShuffleMask);
    break;

  case X86::MOVLHPSrr:
  case X86::VMOVLHPSrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeMOVLHPSMask(2, ShuffleMask);
    break;

  case X86::MOVHLPSrr:
  case X86::VMOVHLPSrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeMOVHLPSMask(2, ShuffleMask);
    break;

  case X86::MOVSLDUPrr:
  case X86::VMOVSLDUPrr:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::MOVSLDUPrm:
  case X86::VMOVSLDUPrm:
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeMOVSLDUPMask(MVT::v4f32, ShuffleMask);
    break;

  case X86::VMOVSHDUPYrr:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VMOVSHDUPYrm:
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeMOVSHDUPMask(MVT::v8f32, ShuffleMask);
    break;

  case X86::VMOVSLDUPYrr:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VMOVSLDUPYrm:
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeMOVSLDUPMask(MVT::v8f32, ShuffleMask);
    break;

  case X86::MOVSHDUPrr:
  case X86::VMOVSHDUPrr:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::MOVSHDUPrm:
  case X86::VMOVSHDUPrm:
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeMOVSHDUPMask(MVT::v4f32, ShuffleMask);
    break;

  case X86::PALIGNR128rr:
  case X86::VPALIGNR128rr:
    Src1Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PALIGNR128rm:
  case X86::VPALIGNR128rm:
    Src2Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePALIGNRMask(MVT::v16i8,
                        MI->getOperand(MI->getNumOperands()-1).getImm(),
                        ShuffleMask);
    break;
  case X86::VPALIGNR256rr:
    Src1Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPALIGNR256rm:
    Src2Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePALIGNRMask(MVT::v32i8,
                        MI->getOperand(MI->getNumOperands()-1).getImm(),
                        ShuffleMask);
    break;

  case X86::PSHUFDri:
  case X86::VPSHUFDri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::PSHUFDmi:
  case X86::VPSHUFDmi:
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFMask(MVT::v4i32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    break;
  case X86::VPSHUFDYri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPSHUFDYmi:
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFMask(MVT::v8i32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    break;


  case X86::PSHUFHWri:
  case X86::VPSHUFHWri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::PSHUFHWmi:
  case X86::VPSHUFHWmi:
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFHWMask(MVT::v8i16,
                        MI->getOperand(MI->getNumOperands()-1).getImm(),
                        ShuffleMask);
    break;
  case X86::VPSHUFHWYri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPSHUFHWYmi:
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFHWMask(MVT::v16i16,
                        MI->getOperand(MI->getNumOperands()-1).getImm(),
                        ShuffleMask);
    break;
  case X86::PSHUFLWri:
  case X86::VPSHUFLWri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::PSHUFLWmi:
  case X86::VPSHUFLWmi:
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFLWMask(MVT::v8i16,
                        MI->getOperand(MI->getNumOperands()-1).getImm(),
                        ShuffleMask);
    break;
  case X86::VPSHUFLWYri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPSHUFLWYmi:
    DestName = getRegName(MI->getOperand(0).getReg());
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFLWMask(MVT::v16i16,
                        MI->getOperand(MI->getNumOperands()-1).getImm(),
                        ShuffleMask);
    break;

  case X86::PUNPCKHBWrr:
  case X86::VPUNPCKHBWrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKHBWrm:
  case X86::VPUNPCKHBWrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v16i8, ShuffleMask);
    break;
  case X86::VPUNPCKHBWYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKHBWYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v32i8, ShuffleMask);
    break;
  case X86::PUNPCKHWDrr:
  case X86::VPUNPCKHWDrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKHWDrm:
  case X86::VPUNPCKHWDrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v8i16, ShuffleMask);
    break;
  case X86::VPUNPCKHWDYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKHWDYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v16i16, ShuffleMask);
    break;
  case X86::PUNPCKHDQrr:
  case X86::VPUNPCKHDQrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKHDQrm:
  case X86::VPUNPCKHDQrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v4i32, ShuffleMask);
    break;
  case X86::VPUNPCKHDQYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKHDQYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v8i32, ShuffleMask);
    break;
  case X86::PUNPCKHQDQrr:
  case X86::VPUNPCKHQDQrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKHQDQrm:
  case X86::VPUNPCKHQDQrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v2i64, ShuffleMask);
    break;
  case X86::VPUNPCKHQDQYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKHQDQYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKHMask(MVT::v4i64, ShuffleMask);
    break;

  case X86::PUNPCKLBWrr:
  case X86::VPUNPCKLBWrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKLBWrm:
  case X86::VPUNPCKLBWrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v16i8, ShuffleMask);
    break;
  case X86::VPUNPCKLBWYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKLBWYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v32i8, ShuffleMask);
    break;
  case X86::PUNPCKLWDrr:
  case X86::VPUNPCKLWDrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKLWDrm:
  case X86::VPUNPCKLWDrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v8i16, ShuffleMask);
    break;
  case X86::VPUNPCKLWDYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKLWDYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v16i16, ShuffleMask);
    break;
  case X86::PUNPCKLDQrr:
  case X86::VPUNPCKLDQrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKLDQrm:
  case X86::VPUNPCKLDQrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v4i32, ShuffleMask);
    break;
  case X86::VPUNPCKLDQYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKLDQYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v8i32, ShuffleMask);
    break;
  case X86::PUNPCKLQDQrr:
  case X86::VPUNPCKLQDQrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::PUNPCKLQDQrm:
  case X86::VPUNPCKLQDQrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v2i64, ShuffleMask);
    break;
  case X86::VPUNPCKLQDQYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPUNPCKLQDQYrm:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    DecodeUNPCKLMask(MVT::v4i64, ShuffleMask);
    break;

  case X86::SHUFPDrri:
  case X86::VSHUFPDrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::SHUFPDrmi:
  case X86::VSHUFPDrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeSHUFPMask(MVT::v2f64,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VSHUFPDYrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VSHUFPDYrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeSHUFPMask(MVT::v4f64,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::SHUFPSrri:
  case X86::VSHUFPSrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::SHUFPSrmi:
  case X86::VSHUFPSrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeSHUFPMask(MVT::v4f32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VSHUFPSYrri:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VSHUFPSYrmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeSHUFPMask(MVT::v8f32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;

  case X86::UNPCKLPDrr:
  case X86::VUNPCKLPDrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::UNPCKLPDrm:
  case X86::VUNPCKLPDrm:
    DecodeUNPCKLMask(MVT::v2f64, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VUNPCKLPDYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VUNPCKLPDYrm:
    DecodeUNPCKLMask(MVT::v4f64, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::UNPCKLPSrr:
  case X86::VUNPCKLPSrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::UNPCKLPSrm:
  case X86::VUNPCKLPSrm:
    DecodeUNPCKLMask(MVT::v4f32, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VUNPCKLPSYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VUNPCKLPSYrm:
    DecodeUNPCKLMask(MVT::v8f32, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::UNPCKHPDrr:
  case X86::VUNPCKHPDrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::UNPCKHPDrm:
  case X86::VUNPCKHPDrm:
    DecodeUNPCKHMask(MVT::v2f64, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VUNPCKHPDYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VUNPCKHPDYrm:
    DecodeUNPCKHMask(MVT::v4f64, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::UNPCKHPSrr:
  case X86::VUNPCKHPSrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::UNPCKHPSrm:
  case X86::VUNPCKHPSrm:
    DecodeUNPCKHMask(MVT::v4f32, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VUNPCKHPSYrr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VUNPCKHPSYrm:
    DecodeUNPCKHMask(MVT::v8f32, ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPERMILPSri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPERMILPSmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFMask(MVT::v4f32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPERMILPSYri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPERMILPSYmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFMask(MVT::v8f32,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPERMILPDri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPERMILPDmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFMask(MVT::v2f64,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPERMILPDYri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPERMILPDYmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodePSHUFMask(MVT::v4f64,
                      MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPERM2F128rr:
  case X86::VPERM2I128rr:
    Src2Name = getRegName(MI->getOperand(2).getReg());
    // FALL THROUGH.
  case X86::VPERM2F128rm:
  case X86::VPERM2I128rm:
    // For instruction comments purpose, assume the 256-bit vector is v4i64.
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeVPERM2X128Mask(MVT::v4i64,
                           MI->getOperand(MI->getNumOperands()-1).getImm(),
                           ShuffleMask);
    Src1Name = getRegName(MI->getOperand(1).getReg());
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  case X86::VPERMQYri:
  case X86::VPERMPDYri:
    Src1Name = getRegName(MI->getOperand(1).getReg());
    // FALL THROUGH.
  case X86::VPERMQYmi:
  case X86::VPERMPDYmi:
    if(MI->getOperand(MI->getNumOperands()-1).isImm())
      DecodeVPERMMask(MI->getOperand(MI->getNumOperands()-1).getImm(),
                      ShuffleMask);
    DestName = getRegName(MI->getOperand(0).getReg());
    break;
  }

  // The only comments we decode are shuffles, so give up if we were unable to
  // decode a shuffle mask.
  if (ShuffleMask.empty())
    return false;

  if (!DestName) DestName = Src1Name;
  OS << (DestName ? DestName : "mem") << " = ";

  // If the two sources are the same, canonicalize the input elements to be
  // from the first src so that we get larger element spans.
  if (Src1Name == Src2Name) {
    for (unsigned i = 0, e = ShuffleMask.size(); i != e; ++i) {
      if ((int)ShuffleMask[i] >= 0 && // Not sentinel.
          ShuffleMask[i] >= (int)e)        // From second mask.
        ShuffleMask[i] -= e;
    }
  }

  // The shuffle mask specifies which elements of the src1/src2 fill in the
  // destination, with a few sentinel values.  Loop through and print them
  // out.
  for (unsigned i = 0, e = ShuffleMask.size(); i != e; ++i) {
    if (i != 0)
      OS << ',';
    if (ShuffleMask[i] == SM_SentinelZero) {
      OS << "zero";
      continue;
    }

    // Otherwise, it must come from src1 or src2.  Print the span of elements
    // that comes from this src.
    bool isSrc1 = ShuffleMask[i] < (int)ShuffleMask.size();
    const char *SrcName = isSrc1 ? Src1Name : Src2Name;
    OS << (SrcName ? SrcName : "mem") << '[';
    bool IsFirst = true;
    while (i != e && (int)ShuffleMask[i] != SM_SentinelZero &&
           (ShuffleMask[i] < (int)ShuffleMask.size()) == isSrc1) {
      if (!IsFirst)
        OS << ',';
      else
        IsFirst = false;
      if (ShuffleMask[i] == SM_SentinelUndef)
        OS << "u";
      else
        OS << ShuffleMask[i] % ShuffleMask.size();
      ++i;
    }
    OS << ']';
    --i;  // For loop increments element #.
  }
  //MI->print(OS, 0);
  OS << "\n";

  // We successfully added a comment to this instruction.
  return true;
}