[mips][microMIPS] Extending size reduction pass with ADDIUSP and ADDIUR1SP

[milena.vujosevic.janicic]

Summary

The patch extends size reduction pass for MicroMIPS.
The following instructions are examined and transformed, if possible:
ADDIU instruction is transformed into 16-bit instruction ADDIUSP
ADDIU instruction is transformed into 16-bit instruction ADDIUR1SP

[sdardis]

Can you re-upload this diff before committing? The paths are cut short, so they're missing test/ and lib/ respectively.

Otherwise, LGTM with some nits on the comments.

Target/Mips/MicroMipsSizeReduction.cpp

35

Nit: "Transfer opernads no 0 and no 2" -> "Transfer operands 0 and 2"

36

Nit; oppernad -> operand.

153

Nit: full stop at the end of this sentence.

158

Nit: full stop at the end of this sentence.

259

Nit: "is ADDIUSP immediate" should be "is a valid immediate for ADDIUSP.".

[sdardis]

lib/Target/Mips/MicroMipsSizeReduction.cpp

35–36 ↗

(On Diff #101670)

opernad -> operand.

259 ↗

(On Diff #101670)

Full stop at the end of this sentence.

CodeGen/Mips/micromips-sizereduction/micromips-addiur1sp-addiusp.ll

+; RUN: llc -march=mipsel -mcpu=mips32r2 -mattr=+micromips -verify-machineinstrs < %s | FileCheck %s
+
+define i32 @f1() {
+entry:
+; CHECK-LABEL: f1:
+; CHECK: addiusp
+; CHECK: addiur1sp
+; CHECK: addiusp
+  %a = alloca [10 x i32], align 4
+  %index = getelementptr inbounds [10 x i32], [10 x i32]* %a, i32 0, i32 0
+  call void @init(i32* %index)
+  %0 = load i32, i32* %index, align 4
+  ret i32 %0
+}
+
+declare void @init(i32*)
+

Target/Mips/MicroMipsSizeReduction.cpp

 
 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
+  OT_Operands02,  ///< Transfer opernads no 0 and no 2
+  OT_Operand2,    ///< Transfer just oppernad no 2
 };
 
 /// Reduction type
 // TODO: Will be extended when additional optimizations are added
 enum ReduceType {
   RT_OneInstr ///< Reduce one instruction into a smaller instruction
 };
 
private:
   // 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);
 
+  // Attempts to reduce ADDIU into ADDIUSP instruction,
+  // returns true on success
+  static bool ReduceADDIUToADDIUSP(MachineInstr *MI,
+                                   const ReduceEntry &Entry);
+
+  // Attempts to reduce ADDIU into ADDIUR1SP instruction,
+  // returns true on success
+  static bool ReduceADDIUToADDIUR1SP(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::ADDiu, Mips::ADDIUR1SP_MM),
+     ReduceADDIUToADDIUR1SP, OpInfo(OT_Operands02), ImmField(2, 0, 64, 2)},
+    {RT_OneInstr, OpCodes(Mips::ADDiu, Mips::ADDIUSP_MM),
+     ReduceADDIUToADDIUSP, OpInfo(OT_Operand2), ImmField(0, 0, 0, 2)},
+    {RT_OneInstr, OpCodes(Mips::ADDiu_MM, Mips::ADDIUR1SP_MM),
+     ReduceADDIUToADDIUR1SP, OpInfo(OT_Operands02), ImmField(2, 0, 64, 2)},
+    {RT_OneInstr, OpCodes(Mips::ADDiu_MM, Mips::ADDIUSP_MM),
+     ReduceADDIUToADDIUSP, OpInfo(OT_Operand2), ImmField(0, 0, 0, 2)},
     {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::LEA_ADDiu, Mips::ADDIUR1SP_MM),
+     ReduceADDIUToADDIUR1SP, OpInfo(OT_Operands02), ImmField(2, 0, 64, 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)},

 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 value is ADDIUSP immediate
+static bool AddiuspImmValue(int64_t Value) {
+  int64_t Value2 = Value >> 2;
+  if (Value == (Value2 << 2) &&
+      ((Value2 >= 2 && Value2 <= 257) || (Value2 >= -258 && Value2 <= -3)))
+    return true;
+  return false;
+}
+
 // 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;
bool MicroMipsSizeReduce::ReduceArithmeticInstructions(
   if (!isMMThreeBitGPRegister(MI->getOperand(0)) ||
       !isMMThreeBitGPRegister(MI->getOperand(1)) ||
       !isMMThreeBitGPRegister(MI->getOperand(2)))
     return false;
 
   return ReplaceInstruction(MI, Entry);
 }
 
+bool MicroMipsSizeReduce::ReduceADDIUToADDIUR1SP(MachineInstr *MI,
+                                                 const ReduceEntry &Entry) {
+
+  if (!ImmInRange(MI, Entry))
+    return false;
+
+  if (!isMMThreeBitGPRegister(MI->getOperand(0)) || !IsSP(MI->getOperand(1)))
+    return false;
+
+  return ReplaceInstruction(MI, Entry);
+}
+
+bool MicroMipsSizeReduce::ReduceADDIUToADDIUSP(MachineInstr *MI,
+                                               const ReduceEntry &Entry) {
+
+  int64_t ImmValue;
+  if (!GetImm(MI, Entry.ImmField(), ImmValue))
+    return false;
+
+  if (!AddiuspImmValue(ImmValue))
+    return false;
+
+  if (!IsSP(MI->getOperand(0)) || !IsSP(MI->getOperand(1)))
+    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)))
bool MicroMipsSizeReduce::ReduceMBB(MachineBasicBlock &MBB) {
   }
 
   return Modified;
 }
 
 bool MicroMipsSizeReduce::ReplaceInstruction(MachineInstr *MI,
                                              const ReduceEntry &Entry) {
 
+  enum OperandTransfer OpTransfer = Entry.TransferOperands();
+  if (OpTransfer == OT_OperandsAll) {
+    DEBUG(dbgs() << "Converted 32-bit: " << *MI);
     MI->setDesc(MipsII->get(Entry.NarrowOpc()));
-  DEBUG(dbgs() << "Converted into 16-bit: " << *MI);
+    DEBUG(dbgs() << "       to 16-bit: " << *MI);
     ++NumReduced;
     return true;
+  } else {
+    MachineBasicBlock &MBB = *MI->getParent();
+    const MCInstrDesc &NewMCID = MipsII->get(Entry.NarrowOpc());
+    DebugLoc dl = MI->getDebugLoc();
+    MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, NewMCID);
+
+    if (OpTransfer == OT_Operand2)
+      MIB.add(MI->getOperand(2));
+    else if (OpTransfer == OT_Operands02) {
+      MIB.add(MI->getOperand(0));
+      MIB.add(MI->getOperand(2));
+    }
+
+    // Transfer MI flags.
+    MIB.setMIFlags(MI->getFlags());
+
+    DEBUG(dbgs() << "Converted 32-bit: " << *MI
+                 << "       to 16-bit: " << *MIB);
+    MBB.erase_instr(MI);
+    ++NumReduced;
+    return true;
+  }
+  return false;
 }
 
 bool MicroMipsSizeReduce::runOnMachineFunction(MachineFunction &MF) {
 
   Subtarget = &static_cast<const MipsSubtarget &>(MF.getSubtarget());
 
   // TODO: Add support for other subtargets:
   // microMIPS32r6 and microMIPS64r6