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diff --git a/contrib/llvm/lib/Target/X86/X86EvexToVex.cpp b/contrib/llvm/lib/Target/X86/X86EvexToVex.cpp
new file mode 100755
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+++ b/contrib/llvm/lib/Target/X86/X86EvexToVex.cpp
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+//===----------------------- X86EvexToVex.cpp ----------------------------===//
+// Compress EVEX instructions to VEX encoding when possible to reduce code size
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+/// \file
+/// This file defines the pass that goes over all AVX-512 instructions which
+/// are encoded using the EVEX prefix and if possible replaces them by their
+/// corresponding VEX encoding which is usually shorter by 2 bytes.
+/// EVEX instructions may be encoded via the VEX prefix when the AVX-512
+/// instruction has a corresponding AVX/AVX2 opcode and when it does not
+/// use the xmm or the mask registers or xmm/ymm registers wuith indexes
+/// higher than 15.
+/// The pass applies code reduction on the generated code for AVX-512 instrs.
+///
+//===---------------------------------------------------------------------===//
+
+#include "InstPrinter/X86InstComments.h"
+#include "X86.h"
+#include "X86InstrBuilder.h"
+#include "X86InstrInfo.h"
+#include "X86InstrTablesInfo.h"
+#include "X86MachineFunctionInfo.h"
+#include "X86Subtarget.h"
+#include "X86TargetMachine.h"
+
+using namespace llvm;
+
+#define EVEX2VEX_DESC "Compressing EVEX instrs to VEX encoding when possible"
+#define EVEX2VEX_NAME "x86-evex-to-vex-compress"
+
+#define DEBUG_TYPE EVEX2VEX_NAME
+
+namespace {
+
+class EvexToVexInstPass : public MachineFunctionPass {
+
+  /// X86EvexToVexCompressTable - Evex to Vex encoding opcode map.
+  typedef DenseMap<unsigned, uint16_t> EvexToVexTableType;
+  EvexToVexTableType EvexToVex128Table;
+  EvexToVexTableType EvexToVex256Table;
+
+  /// For EVEX instructions that can be encoded using VEX encoding, replace
+  /// them by the VEX encoding in order to reduce size.
+  bool CompressEvexToVexImpl(MachineInstr &MI) const;
+
+  /// For initializing the hash map tables of all AVX-512 EVEX
+  /// corresponding to AVX/AVX2 opcodes.
+  void AddTableEntry(EvexToVexTableType &EvexToVexTable, uint16_t EvexOp,
+                     uint16_t VexOp);
+
+public:
+  static char ID;
+
+  StringRef getPassName() const override { return EVEX2VEX_DESC; }
+
+  EvexToVexInstPass() : MachineFunctionPass(ID) {
+    initializeEvexToVexInstPassPass(*PassRegistry::getPassRegistry());
+
+    // Initialize the EVEX to VEX 128 table map.
+    for (X86EvexToVexCompressTableEntry Entry : X86EvexToVex128CompressTable) {
+      AddTableEntry(EvexToVex128Table, Entry.EvexOpcode, Entry.VexOpcode);
+    }
+
+    // Initialize the EVEX to VEX 256 table map.
+    for (X86EvexToVexCompressTableEntry Entry : X86EvexToVex256CompressTable) {
+      AddTableEntry(EvexToVex256Table, Entry.EvexOpcode, Entry.VexOpcode);
+    }
+  }
+
+  /// Loop over all of the basic blocks, replacing EVEX instructions
+  /// by equivalent VEX instructions when possible for reducing code size.
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  // This pass runs after regalloc and doesn't support VReg operands.
+  MachineFunctionProperties getRequiredProperties() const override {
+    return MachineFunctionProperties().set(
+        MachineFunctionProperties::Property::NoVRegs);
+  }
+
+private:
+  /// Machine instruction info used throughout the class.
+  const X86InstrInfo *TII;
+};
+
+char EvexToVexInstPass::ID = 0;
+}
+
+INITIALIZE_PASS(EvexToVexInstPass, EVEX2VEX_NAME, EVEX2VEX_DESC, false, false)
+
+FunctionPass *llvm::createX86EvexToVexInsts() {
+  return new EvexToVexInstPass();
+}
+
+bool EvexToVexInstPass::runOnMachineFunction(MachineFunction &MF) {
+  TII = MF.getSubtarget<X86Subtarget>().getInstrInfo();
+
+  const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
+  if (!ST.hasAVX512())
+    return false;
+
+  bool Changed = false;
+
+  /// Go over all basic blocks in function and replace
+  /// EVEX encoded instrs by VEX encoding when possible.
+  for (MachineBasicBlock &MBB : MF) {
+
+    // Traverse the basic block. 
+    for (MachineInstr &MI : MBB)      
+      Changed |= CompressEvexToVexImpl(MI);
+  }
+
+  return Changed;
+}
+
+void EvexToVexInstPass::AddTableEntry(EvexToVexTableType &EvexToVexTable,
+                                      uint16_t EvexOp, uint16_t VexOp) {
+  EvexToVexTable[EvexOp] = VexOp;
+}
+
+// For EVEX instructions that can be encoded using VEX encoding
+// replace them by the VEX encoding in order to reduce size.
+bool EvexToVexInstPass::CompressEvexToVexImpl(MachineInstr &MI) const {
+
+  // VEX format.
+  // # of bytes: 0,2,3  1      1      0,1   0,1,2,4  0,1
+  //  [Prefixes] [VEX]  OPCODE ModR/M [SIB] [DISP]  [IMM]
+  //
+  // EVEX format.
+  //  # of bytes: 4    1      1      1      4       / 1         1
+  //  [Prefixes]  EVEX Opcode ModR/M [SIB] [Disp32] / [Disp8*N] [Immediate]
+
+  const MCInstrDesc &Desc = MI.getDesc();
+
+  // Check for EVEX instructions only.
+  if ((Desc.TSFlags & X86II::EncodingMask) != X86II::EVEX)
+    return false;
+ 
+  // Check for EVEX instructions with mask or broadcast as in these cases 
+  // the EVEX prefix is needed in order to carry this information 
+  // thus preventing the transformation to VEX encoding.
+  if (Desc.TSFlags & (X86II::EVEX_K | X86II::EVEX_B))
+    return false;
+ 
+  // Check for non EVEX_V512 instrs only.
+  // EVEX_V512 instr: bit EVEX_L2 = 1; bit VEX_L = 0.
+  if ((Desc.TSFlags & X86II::EVEX_L2) && !(Desc.TSFlags & X86II::VEX_L))
+    return false;  
+        
+  // EVEX_V128 instr: bit EVEX_L2 = 0, bit VEX_L = 0.
+  bool IsEVEX_V128 =
+      (!(Desc.TSFlags & X86II::EVEX_L2) && !(Desc.TSFlags & X86II::VEX_L));
+
+  // EVEX_V256 instr: bit EVEX_L2 = 0, bit VEX_L = 1.
+  bool IsEVEX_V256 =
+      (!(Desc.TSFlags & X86II::EVEX_L2) && (Desc.TSFlags & X86II::VEX_L));
+
+  unsigned NewOpc = 0;
+
+  // Check for EVEX_V256 instructions.
+  if (IsEVEX_V256) {
+    // Search for opcode in the EvexToVex256 table.
+    auto It = EvexToVex256Table.find(MI.getOpcode());
+    if (It != EvexToVex256Table.end())
+      NewOpc = It->second;
+  }
+
+  // Check for EVEX_V128 or Scalar instructions.
+  else if (IsEVEX_V128) {
+    // Search for opcode in the EvexToVex128 table.
+    auto It = EvexToVex128Table.find(MI.getOpcode());
+    if (It != EvexToVex128Table.end())
+      NewOpc = It->second;
+  }
+
+  if (!NewOpc)
+    return false;
+
+  auto isHiRegIdx = [](unsigned Reg) {
+    // Check for XMM register with indexes between 16 - 31.
+    if (Reg >= X86::XMM16 && Reg <= X86::XMM31)
+      return true;
+
+    // Check for YMM register with indexes between 16 - 31.
+    if (Reg >= X86::YMM16 && Reg <= X86::YMM31)
+      return true;
+
+    return false;
+  };
+
+  // Check that operands are not ZMM regs or
+  // XMM/YMM regs with hi indexes between 16 - 31.
+  for (const MachineOperand &MO : MI.explicit_operands()) {
+    if (!MO.isReg())
+      continue;
+
+    unsigned Reg = MO.getReg();
+
+    assert (!(Reg >= X86::ZMM0 && Reg <= X86::ZMM31));
+
+    if (isHiRegIdx(Reg))
+      return false;
+  }
+ 
+  const MCInstrDesc &MCID = TII->get(NewOpc);
+  MI.setDesc(MCID);
+  MI.setAsmPrinterFlag(AC_EVEX_2_VEX);
+  return true; 
+}