Merge clang, llvm, lld, lldb, compiler-rt and libc++ 5.0.0 release.

MFC r309126 (by emaste):

  Correct lld llvm-tblgen dependency file name

MFC r309169:

  Get rid of separate Subversion mergeinfo properties for llvm-dwarfdump
  and llvm-lto.  The mergeinfo confuses Subversion enormously, and these
  directories will just use the mergeinfo for llvm itself.

MFC r312765:

  Pull in r276136 from upstream llvm trunk (by Wei Mi):

    Use ValueOffsetPair to enhance value reuse during SCEV expansion.

    In D12090, the ExprValueMap was added to reuse existing value during
    SCEV expansion. However, const folding and sext/zext distribution can
    make the reuse still difficult.

    A simplified case is: suppose we know S1 expands to V1 in
    ExprValueMap, and
      S1 = S2 + C_a
      S3 = S2 + C_b
    where C_a and C_b are different SCEVConstants. Then we'd like to
    expand S3 as V1 - C_a + C_b instead of expanding S2 literally. It is
    helpful when S2 is a complex SCEV expr and S2 has no entry in
    ExprValueMap, which is usually caused by the fact that S3 is
    generated from S1 after const folding.

    In order to do that, we represent ExprValueMap as a mapping from SCEV
    to ValueOffsetPair. We will save both S1->{V1, 0} and S2->{V1, C_a}
    into the ExprValueMap when we create SCEV for V1. When S3 is
    expanded, it will first expand S2 to V1 - C_a because of S2->{V1,
    C_a} in the map, then expand S3 to V1 - C_a + C_b.

    Differential Revision: https://reviews.llvm.org/D21313

  This should fix assertion failures when building OpenCV >= 3.1.

  PR:		215649

MFC r312831:

  Revert r312765 for now, since it causes assertions when building
  lang/spidermonkey24.

  Reported by:	antoine
  PR:		215649

MFC r316511 (by jhb):

  Add an implementation of __ffssi2() derived from __ffsdi2().

  Newer versions of GCC include an __ffssi2() symbol in libgcc and the
  compiler can emit calls to it in generated code.  This is true for at
  least GCC 6.2 when compiling world for mips and mips64.

  Reviewed by:	jmallett, dim
  Sponsored by:	DARPA / AFRL
  Differential Revision:	https://reviews.freebsd.org/D10086

MFC r318601 (by adrian):

  [libcompiler-rt] add bswapdi2/bswapsi2

  This is required for mips gcc 6.3 userland to build/run.

  Reviewed by:	emaste, dim
  Approved by:	emaste
  Differential Revision:	https://reviews.freebsd.org/D10838

MFC r318884 (by emaste):

  lldb: map TRAP_CAP to a trace trap

  In the absense of a more specific handler for TRAP_CAP (generated by
  ENOTCAPABLE or ECAPMODE while in capability mode) treat it as a trace
  trap.

  Example usage (testing the bug in PR219173):

  % proccontrol -m trapcap lldb usr.bin/hexdump/obj/hexdump -- -Cv -s 1 /bin/ls
  ...
  (lldb) run
  Process 12980 launching
  Process 12980 launched: '.../usr.bin/hexdump/obj/hexdump' (x86_64)
  Process 12980 stopped
  * thread #1, stop reason = trace
      frame #0: 0x0000004b80c65f1a libc.so.7`__sys_lseek + 10
  ...

  In the future we should have LLDB control the trapcap procctl itself
  (as it does with ASLR), as well as report a specific stop reason.
  This change eliminates an assertion failure from LLDB for now.

MFC r319796:

  Remove a few unneeded files from libllvm, libclang and liblldb.

MFC r319885 (by emaste):

  lld: ELF: Fix ICF crash on absolute symbol relocations.

  If two sections contained relocations to absolute symbols with the same
  value we would crash when trying to access their sections. Add a check that
  both symbols point to sections before accessing their sections, and treat
  absolute symbols as equal if their values are equal.

  Obtained from:	LLD commit r292578

MFC r319918:

  Revert r319796 for now, it can cause undefined references when linking
  in some circumstances.

  Reported by:	Shawn Webb <shawn.webb@hardenedbsd.org>

MFC r319957 (by emaste):

  lld: Add armelf emulation mode

  Obtained from:	LLD r305375

MFC r321369:

  Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
  5.0.0 (trunk r308421).  Upstream has branched for the 5.0.0 release,
  which should be in about a month.  Please report bugs and regressions,
  so we can get them into the release.

  Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
  support to build; see UPDATING for more information.

MFC r321420:

  Add a few more object files to liblldb, which should solve errors when
  linking the lldb executable in some cases.  In particular, when the
  -ffunction-sections -fdata-sections options are turned off, or
  ineffective.

  Reported by:	Shawn Webb, Mark Millard

MFC r321433:

  Cleanup stale Options.inc files from the previous libllvm build for
  clang 4.0.0.  Otherwise, these can get included before the two newly
  generated ones (which are different) for clang 5.0.0.

  Reported by:	Mark Millard

MFC r321439 (by bdrewery):

  Move llvm Options.inc hack from r321433 for NO_CLEAN to lib/clang/libllvm.

  The files are only ever generated to .OBJDIR, not to WORLDTMP (as a
  sysroot) and are only ever included from a compilation.  So using
  a beforebuild target here removes the file before the compilation
  tries to include it.

MFC r321664:

  Pull in r308891 from upstream llvm trunk (by Benjamin Kramer):

    [CodeGenPrepare] Cut off FindAllMemoryUses if there are too many uses.

    This avoids excessive compile time. The case I'm looking at is
    Function.cpp from an old version of LLVM that still had the giant
    memcmp string matcher in it. Before r308322 this compiled in about 2
    minutes, after it, clang takes infinite* time to compile it. With
    this patch we're at 5 min, which is still bad but this is a
    pathological case.

    The cut off at 20 uses was chosen by looking at other cut-offs in LLVM
    for user scanning. It's probably too high, but does the job and is
    very unlikely to regress anything.

    Fixes PR33900.

    * I'm impatient and aborted after 15 minutes, on the bug report it was
      killed after 2h.

  Pull in r308986 from upstream llvm trunk (by Simon Pilgrim):

    [X86][CGP] Reduce memcmp() expansion to 2 load pairs (PR33914)

    D35067/rL308322 attempted to support up to 4 load pairs for memcmp
    inlining which resulted in regressions for some optimized libc memcmp
    implementations (PR33914).

    Until we can match these more optimal cases, this patch reduces the
    memcmp expansion to a maximum of 2 load pairs (which matches what we
    do for -Os).

    This patch should be considered for the 5.0.0 release branch as well

    Differential Revision: https://reviews.llvm.org/D35830

  These fix a hang (or extremely long compile time) when building older
  LLVM ports.

  Reported by:    antoine
  PR:             219139

MFC r321719:

  Pull in r309503 from upstream clang trunk (by Richard Smith):

    PR33902: Invalidate line number cache when adding more text to
    existing buffer.

    This led to crashes as the line number cache would report a bogus
    line number for a line of code, and we'd try to find a nonexistent
    column within the line when printing diagnostics.

  This fixes an assertion when building the graphics/champlain port.

  Reported by:	antoine, kwm
  PR:		219139

MFC r321723:

  Upgrade our copies of clang, llvm, lld and lldb to r309439 from the
  upstream release_50 branch.  This is just after upstream's 5.0.0-rc1.

MFC r322320:

  Upgrade our copies of clang, llvm and libc++ to r310316 from the
  upstream release_50 branch.

MFC r322326 (by emaste):

  lldb: Make i386-*-freebsd expression work on JIT path

  * Enable i386 ABI creation for freebsd
  * Added an extra argument in ABISysV_i386::PrepareTrivialCall for mmap
    syscall
  * Unlike linux, the last argument of mmap is actually 64-bit(off_t).
    This requires us to push an additional word for the higher order bits.
  * Prior to this change, ktrace dump will show mmap failures due to
    invalid argument coming from the 6th mmap argument.

  Submitted by:	Karnajit Wangkhem
  Differential Revision:	https://reviews.llvm.org/D34776

MFC r322360 (by emaste):

  lldb: Report inferior signals as signals, not exceptions, on FreeBSD

  This is the FreeBSD equivalent of LLVM r238549.

  This serves 2 purposes:

  * LLDB should handle inferior process signals SIGSEGV/SIGILL/SIGBUS/
    SIGFPE the way it is suppose to be handled. Prior to this fix these
    signals will neither create a coredump, nor exit from the debugger
    or work for signal handling scenario.
  * eInvalidCrashReason need not report "unknown crash reason" if we have
    a valid si_signo

  llvm.org/pr23699

  Patch by Karnajit Wangkhem

  Differential Revision:  https://reviews.llvm.org/D35223

  Submitted by:	Karnajit Wangkhem
  Obtained from:	LLVM r310591

MFC r322474 (by emaste):

  lld: Add `-z muldefs` option.

  Obtained from:	LLVM r310757

MFC r322740:

  Upgrade our copies of clang, llvm, lld and libc++ to r311219 from the
  upstream release_50 branch.

MFC r322855:

  Upgrade our copies of clang, llvm, lldb and compiler-rt to r311606 from
  the upstream release_50 branch.

  As of this version, lib/msun's trig test should also work correctly
  again (see bug 220989 for more information).

  PR:		220989

MFC r323112:

  Upgrade our copies of clang, llvm, lldb and compiler-rt to r312293 from
  the upstream release_50 branch.  This corresponds to 5.0.0 rc4.

  As of this version, the cad/stepcode port should now compile in a more
  reasonable time on i386 (see bug 221836 for more information).

  PR:		221836

MFC r323245:

  Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
  5.0.0 release (upstream r312559).

  Release notes for llvm, clang and lld will be available here soon:
  <http://releases.llvm.org/5.0.0/docs/ReleaseNotes.html>
  <http://releases.llvm.org/5.0.0/tools/clang/docs/ReleaseNotes.html>
  <http://releases.llvm.org/5.0.0/tools/lld/docs/ReleaseNotes.html>

  Relnotes:	yes

(cherry picked from commit 12cd91cf4c6b96a24427c0de5374916f2808d263)

1 files changed, 392 insertions, 0 deletions

diff --git a/contrib/llvm/lib/Target/Mips/MicroMipsSizeReduction.cpp b/contrib/llvm/lib/Target/Mips/MicroMipsSizeReduction.cpp
new file mode 100644
index 0000000..35948e3
--- /dev/null
+++ b/contrib/llvm/lib/Target/Mips/MicroMipsSizeReduction.cpp
@@ -0,0 +1,392 @@
+//=== MicroMipsSizeReduction.cpp - MicroMips size reduction pass --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///\file
+/// This pass is used to reduce the size of instructions where applicable.
+///
+/// TODO: Implement microMIPS64 support.
+/// TODO: Implement support for reducing into lwp/swp instruction.
+//===----------------------------------------------------------------------===//
+#include "Mips.h"
+#include "MipsInstrInfo.h"
+#include "MipsSubtarget.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "micromips-reduce-size"
+
+STATISTIC(NumReduced, "Number of 32-bit instructions reduced to 16-bit ones");
+
+namespace {
+
+/// Order of operands to transfer
+// TODO: Will be extended when additional optimizations are added
+enum OperandTransfer {
+  OT_NA,          ///< Not applicable
+  OT_OperandsAll, ///< Transfer all operands
+};
+
+/// Reduction type
+// TODO: Will be extended when additional optimizations are added
+enum ReduceType {
+  RT_OneInstr ///< Reduce one instruction into a smaller instruction
+};
+
+// Information about immediate field restrictions
+struct ImmField {
+  ImmField() : ImmFieldOperand(-1), Shift(0), LBound(0), HBound(0) {}
+  ImmField(uint8_t Shift, int16_t LBound, int16_t HBound,
+           int8_t ImmFieldOperand)
+      : ImmFieldOperand(ImmFieldOperand), Shift(Shift), LBound(LBound),
+        HBound(HBound) {}
+  int8_t ImmFieldOperand; // Immediate operand, -1 if it does not exist
+  uint8_t Shift;          // Shift value
+  int16_t LBound;         // Low bound of the immediate operand
+  int16_t HBound;         // High bound of the immediate operand
+};
+
+/// Information about operands
+// TODO: Will be extended when additional optimizations are added
+struct OpInfo {
+  OpInfo(enum OperandTransfer TransferOperands)
+      : TransferOperands(TransferOperands) {}
+  OpInfo() : TransferOperands(OT_NA) {}
+
+  enum OperandTransfer
+      TransferOperands; ///< Operands to transfer to the new instruction
+};
+
+// Information about opcodes
+struct OpCodes {
+  OpCodes(unsigned WideOpc, unsigned NarrowOpc)
+      : WideOpc(WideOpc), NarrowOpc(NarrowOpc) {}
+
+  unsigned WideOpc;   ///< Wide opcode
+  unsigned NarrowOpc; ///< Narrow opcode
+};
+
+/// ReduceTable - A static table with information on mapping from wide
+/// opcodes to narrow
+struct ReduceEntry {
+
+  enum ReduceType eRType; ///< Reduction type
+  bool (*ReduceFunction)(
+      MachineInstr *MI,
+      const ReduceEntry &Entry); ///< Pointer to reduce function
+  struct OpCodes Ops;            ///< All relevant OpCodes
+  struct OpInfo OpInf;           ///< Characteristics of operands
+  struct ImmField Imm;           ///< Characteristics of immediate field
+
+  ReduceEntry(enum ReduceType RType, struct OpCodes Op,
+              bool (*F)(MachineInstr *MI, const ReduceEntry &Entry),
+              struct OpInfo OpInf, struct ImmField Imm)
+      : eRType(RType), ReduceFunction(F), Ops(Op), OpInf(OpInf), Imm(Imm) {}
+
+  unsigned NarrowOpc() const { return Ops.NarrowOpc; }
+  unsigned WideOpc() const { return Ops.WideOpc; }
+  int16_t LBound() const { return Imm.LBound; }
+  int16_t HBound() const { return Imm.HBound; }
+  uint8_t Shift() const { return Imm.Shift; }
+  int8_t ImmField() const { return Imm.ImmFieldOperand; }
+  enum OperandTransfer TransferOperands() const {
+    return OpInf.TransferOperands;
+  }
+  enum ReduceType RType() const { return eRType; }
+
+  // operator used by std::equal_range
+  bool operator<(const unsigned int r) const { return (WideOpc() < r); }
+
+  // operator used by std::equal_range
+  friend bool operator<(const unsigned int r, const struct ReduceEntry &re) {
+    return (r < re.WideOpc());
+  }
+};
+
+class MicroMipsSizeReduce : public MachineFunctionPass {
+public:
+  static char ID;
+  MicroMipsSizeReduce();
+
+  static const MipsInstrInfo *MipsII;
+  const MipsSubtarget *Subtarget;
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  llvm::StringRef getPassName() const override {
+    return "microMIPS instruction size reduction pass";
+  }
+
+private:
+  /// Reduces width of instructions in the specified basic block.
+  bool ReduceMBB(MachineBasicBlock &MBB);
+
+  /// Attempts to reduce MI, returns true on success.
+  bool ReduceMI(const MachineBasicBlock::instr_iterator &MII);
+
+  // Attempts to reduce LW/SW instruction into LWSP/SWSP,
+  // returns true on success.
+  static bool ReduceXWtoXWSP(MachineInstr *MI, const ReduceEntry &Entry);
+
+  // Attempts to reduce LBU/LHU instruction into LBU16/LHU16,
+  // returns true on success.
+  static bool ReduceLXUtoLXU16(MachineInstr *MI, const ReduceEntry &Entry);
+
+  // Attempts to reduce SB/SH instruction into SB16/SH16,
+  // returns true on success.
+  static bool ReduceSXtoSX16(MachineInstr *MI, const ReduceEntry &Entry);
+
+  // Attempts to reduce arithmetic instructions, returns true on success
+  static bool ReduceArithmeticInstructions(MachineInstr *MI,
+                                           const ReduceEntry &Entry);
+
+  // Changes opcode of an instruction
+  static bool ReplaceInstruction(MachineInstr *MI, const ReduceEntry &Entry);
+
+  // Table with transformation rules for each instruction
+  static llvm::SmallVector<ReduceEntry, 16> ReduceTable;
+};
+
+char MicroMipsSizeReduce::ID = 0;
+const MipsInstrInfo *MicroMipsSizeReduce::MipsII;
+
+// This table must be sorted by WideOpc as a main criterion and
+// ReduceType as a sub-criterion (when wide opcodes are the same)
+llvm::SmallVector<ReduceEntry, 16> MicroMipsSizeReduce::ReduceTable = {
+
+    // ReduceType, OpCodes, ReduceFunction,
+    // OpInfo(TransferOperands),
+    // ImmField(Shift, LBound, HBound, ImmFieldPosition)
+    {RT_OneInstr, OpCodes(Mips::ADDu, Mips::ADDU16_MM),
+     ReduceArithmeticInstructions, OpInfo(OT_OperandsAll),
+     ImmField(0, 0, 0, -1)},
+    {RT_OneInstr, OpCodes(Mips::ADDu_MM, Mips::ADDU16_MM),
+     ReduceArithmeticInstructions, OpInfo(OT_OperandsAll),
+     ImmField(0, 0, 0, -1)},
+    {RT_OneInstr, OpCodes(Mips::LBu, Mips::LBU16_MM), ReduceLXUtoLXU16,
+     OpInfo(OT_OperandsAll), ImmField(0, -1, 15, 2)},
+    {RT_OneInstr, OpCodes(Mips::LBu_MM, Mips::LBU16_MM), ReduceLXUtoLXU16,
+     OpInfo(OT_OperandsAll), ImmField(0, -1, 15, 2)},
+    {RT_OneInstr, OpCodes(Mips::LHu, Mips::LHU16_MM), ReduceLXUtoLXU16,
+     OpInfo(OT_OperandsAll), ImmField(1, 0, 16, 2)},
+    {RT_OneInstr, OpCodes(Mips::LHu_MM, Mips::LHU16_MM), ReduceLXUtoLXU16,
+     OpInfo(OT_OperandsAll), ImmField(1, 0, 16, 2)},
+    {RT_OneInstr, OpCodes(Mips::LW, Mips::LWSP_MM), ReduceXWtoXWSP,
+     OpInfo(OT_OperandsAll), ImmField(2, 0, 32, 2)},
+    {RT_OneInstr, OpCodes(Mips::LW_MM, Mips::LWSP_MM), ReduceXWtoXWSP,
+     OpInfo(OT_OperandsAll), ImmField(2, 0, 32, 2)},
+    {RT_OneInstr, OpCodes(Mips::SB, Mips::SB16_MM), ReduceSXtoSX16,
+     OpInfo(OT_OperandsAll), ImmField(0, 0, 16, 2)},
+    {RT_OneInstr, OpCodes(Mips::SB_MM, Mips::SB16_MM), ReduceSXtoSX16,
+     OpInfo(OT_OperandsAll), ImmField(0, 0, 16, 2)},
+    {RT_OneInstr, OpCodes(Mips::SH, Mips::SH16_MM), ReduceSXtoSX16,
+     OpInfo(OT_OperandsAll), ImmField(1, 0, 16, 2)},
+    {RT_OneInstr, OpCodes(Mips::SH_MM, Mips::SH16_MM), ReduceSXtoSX16,
+     OpInfo(OT_OperandsAll), ImmField(1, 0, 16, 2)},
+    {RT_OneInstr, OpCodes(Mips::SUBu, Mips::SUBU16_MM),
+     ReduceArithmeticInstructions, OpInfo(OT_OperandsAll),
+     ImmField(0, 0, 0, -1)},
+    {RT_OneInstr, OpCodes(Mips::SUBu_MM, Mips::SUBU16_MM),
+     ReduceArithmeticInstructions, OpInfo(OT_OperandsAll),
+     ImmField(0, 0, 0, -1)},
+    {RT_OneInstr, OpCodes(Mips::SW, Mips::SWSP_MM), ReduceXWtoXWSP,
+     OpInfo(OT_OperandsAll), ImmField(2, 0, 32, 2)},
+    {RT_OneInstr, OpCodes(Mips::SW_MM, Mips::SWSP_MM), ReduceXWtoXWSP,
+     OpInfo(OT_OperandsAll), ImmField(2, 0, 32, 2)},
+};
+}
+
+// Returns true if the machine operand MO is register SP
+static bool IsSP(const MachineOperand &MO) {
+  if (MO.isReg() && ((MO.getReg() == Mips::SP)))
+    return true;
+  return false;
+}
+
+// Returns true if the machine operand MO is register $16, $17, or $2-$7.
+static bool isMMThreeBitGPRegister(const MachineOperand &MO) {
+  if (MO.isReg() && Mips::GPRMM16RegClass.contains(MO.getReg()))
+    return true;
+  return false;
+}
+
+// Returns true if the machine operand MO is register $0, $17, or $2-$7.
+static bool isMMSourceRegister(const MachineOperand &MO) {
+  if (MO.isReg() && Mips::GPRMM16ZeroRegClass.contains(MO.getReg()))
+    return true;
+  return false;
+}
+
+// Returns true if the operand Op is an immediate value
+// and writes the immediate value into variable Imm
+static bool GetImm(MachineInstr *MI, unsigned Op, int64_t &Imm) {
+
+  if (!MI->getOperand(Op).isImm())
+    return false;
+  Imm = MI->getOperand(Op).getImm();
+  return true;
+}
+
+// Returns true if the variable Value has the number of least-significant zero
+// bits equal to Shift and if the shifted value is between the bounds
+static bool InRange(int64_t Value, unsigned short Shift, int LBound,
+                    int HBound) {
+  int64_t Value2 = Value >> Shift;
+  if ((Value2 << Shift) == Value && (Value2 >= LBound) && (Value2 < HBound))
+    return true;
+  return false;
+}
+
+// Returns true if immediate operand is in range
+static bool ImmInRange(MachineInstr *MI, const ReduceEntry &Entry) {
+
+  int64_t offset;
+
+  if (!GetImm(MI, Entry.ImmField(), offset))
+    return false;
+
+  if (!InRange(offset, Entry.Shift(), Entry.LBound(), Entry.HBound()))
+    return false;
+
+  return true;
+}
+
+MicroMipsSizeReduce::MicroMipsSizeReduce() : MachineFunctionPass(ID) {}
+
+bool MicroMipsSizeReduce::ReduceMI(
+    const MachineBasicBlock::instr_iterator &MII) {
+
+  MachineInstr *MI = &*MII;
+  unsigned Opcode = MI->getOpcode();
+
+  // Search the table.
+  llvm::SmallVector<ReduceEntry, 16>::const_iterator Start =
+      std::begin(ReduceTable);
+  llvm::SmallVector<ReduceEntry, 16>::const_iterator End =
+      std::end(ReduceTable);
+
+  std::pair<llvm::SmallVector<ReduceEntry, 16>::const_iterator,
+            llvm::SmallVector<ReduceEntry, 16>::const_iterator>
+      Range = std::equal_range(Start, End, Opcode);
+
+  if (Range.first == Range.second)
+    return false;
+
+  for (llvm::SmallVector<ReduceEntry, 16>::const_iterator Entry = Range.first;
+       Entry != Range.second; ++Entry)
+    if (((*Entry).ReduceFunction)(&(*MII), *Entry))
+      return true;
+
+  return false;
+}
+
+bool MicroMipsSizeReduce::ReduceXWtoXWSP(MachineInstr *MI,
+                                         const ReduceEntry &Entry) {
+
+  if (!ImmInRange(MI, Entry))
+    return false;
+
+  if (!IsSP(MI->getOperand(1)))
+    return false;
+
+  return ReplaceInstruction(MI, Entry);
+}
+
+bool MicroMipsSizeReduce::ReduceArithmeticInstructions(
+    MachineInstr *MI, const ReduceEntry &Entry) {
+
+  if (!isMMThreeBitGPRegister(MI->getOperand(0)) ||
+      !isMMThreeBitGPRegister(MI->getOperand(1)) ||
+      !isMMThreeBitGPRegister(MI->getOperand(2)))
+    return false;
+
+  return ReplaceInstruction(MI, Entry);
+}
+
+bool MicroMipsSizeReduce::ReduceLXUtoLXU16(MachineInstr *MI,
+                                           const ReduceEntry &Entry) {
+
+  if (!ImmInRange(MI, Entry))
+    return false;
+
+  if (!isMMThreeBitGPRegister(MI->getOperand(0)) ||
+      !isMMThreeBitGPRegister(MI->getOperand(1)))
+    return false;
+
+  return ReplaceInstruction(MI, Entry);
+}
+
+bool MicroMipsSizeReduce::ReduceSXtoSX16(MachineInstr *MI,
+                                         const ReduceEntry &Entry) {
+
+  if (!ImmInRange(MI, Entry))
+    return false;
+
+  if (!isMMSourceRegister(MI->getOperand(0)) ||
+      !isMMThreeBitGPRegister(MI->getOperand(1)))
+    return false;
+
+  return ReplaceInstruction(MI, Entry);
+}
+
+bool MicroMipsSizeReduce::ReduceMBB(MachineBasicBlock &MBB) {
+  bool Modified = false;
+  MachineBasicBlock::instr_iterator MII = MBB.instr_begin(),
+                                    E = MBB.instr_end();
+  MachineBasicBlock::instr_iterator NextMII;
+
+  // Iterate through the instructions in the basic block
+  for (; MII != E; MII = NextMII) {
+    NextMII = std::next(MII);
+    MachineInstr *MI = &*MII;
+
+    // Don't reduce bundled instructions or pseudo operations
+    if (MI->isBundle() || MI->isTransient())
+      continue;
+
+    // Try to reduce 32-bit instruction into 16-bit instruction
+    Modified |= ReduceMI(MII);
+  }
+
+  return Modified;
+}
+
+bool MicroMipsSizeReduce::ReplaceInstruction(MachineInstr *MI,
+                                             const ReduceEntry &Entry) {
+
+  MI->setDesc(MipsII->get(Entry.NarrowOpc()));
+  DEBUG(dbgs() << "Converted into 16-bit: " << *MI);
+  ++NumReduced;
+  return true;
+}
+
+bool MicroMipsSizeReduce::runOnMachineFunction(MachineFunction &MF) {
+
+  Subtarget = &static_cast<const MipsSubtarget &>(MF.getSubtarget());
+
+  // TODO: Add support for other subtargets:
+  // microMIPS32r6 and microMIPS64r6
+  if (!Subtarget->inMicroMipsMode() || !Subtarget->hasMips32r2())
+    return false;
+
+  MipsII = static_cast<const MipsInstrInfo *>(Subtarget->getInstrInfo());
+
+  bool Modified = false;
+  MachineFunction::iterator I = MF.begin(), E = MF.end();
+
+  for (; I != E; ++I)
+    Modified |= ReduceMBB(*I);
+  return Modified;
+}
+
+/// Returns an instance of the MicroMips size reduction pass.
+FunctionPass *llvm::createMicroMipsSizeReductionPass() {
+  return new MicroMipsSizeReduce();
+}