Pass to replace tranfer/copy instructions into combine instruction where possible.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154695 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 484 insertions, 0 deletions

diff --git a/lib/Target/Hexagon/CMakeLists.txt b/lib/Target/Hexagon/CMakeLists.txt
index 8a49cd8..7f4192c 100644
--- a/lib/Target/Hexagon/CMakeLists.txt
+++ b/lib/Target/Hexagon/CMakeLists.txt
@@ -29,6 +29,8 @@ add_llvm_target(HexagonCodeGen
   HexagonTargetMachine.cpp
   HexagonTargetObjectFile.cpp
   HexagonVLIWPacketizer.cpp
+  HexagonNewValueJump.cpp
+  HexagonCopyToCombine.cpp
 )
 
 add_subdirectory(TargetInfo)
diff --git a/lib/Target/Hexagon/Hexagon.h b/lib/Target/Hexagon/Hexagon.h
index 43858b9..2738df3 100644
--- a/lib/Target/Hexagon/Hexagon.h
+++ b/lib/Target/Hexagon/Hexagon.h
@@ -40,6 +40,8 @@ namespace llvm {
   FunctionPass *createHexagonHardwareLoops();
   FunctionPass *createHexagonPeephole();
   FunctionPass *createHexagonFixupHwLoops();
+  FunctionPass *createHexagonNewValueJump();
+  FunctionPass *createHexagonCopyToCombine();
   FunctionPass *createHexagonPacketizer();
 
 /* TODO: object output.
diff --git a/lib/Target/Hexagon/HexagonCopyToCombine.cpp b/lib/Target/Hexagon/HexagonCopyToCombine.cpp
new file mode 100644
index 0000000..90ff543
--- /dev/null
+++ b/lib/Target/Hexagon/HexagonCopyToCombine.cpp
@@ -0,0 +1,473 @@
+//===------- HexagonCopyToCombine.cpp - Hexagon Copy-To-Combine Pass ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// This pass replaces transfer instructions by combine instructions.
+// We walk along a basic block and look for two combinable instructions and try
+// to move them together. If we can move them next to each other we do so and
+// replace them with a combine instruction.
+//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "hexagon-copy-combine"
+
+#include "llvm/PassSupport.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include "Hexagon.h"
+#include "HexagonInstrInfo.h"
+#include "HexagonRegisterInfo.h"
+#include "HexagonSubtarget.h"
+#include "HexagonTargetMachine.h"
+#include "HexagonMachineFunctionInfo.h"
+
+using namespace llvm;
+
+static
+cl::opt<bool> IsCombinesDisabled("disable-merge-into-combines",
+                                 cl::Hidden, cl::ZeroOrMore,
+                                 cl::init(false),
+                                 cl::desc("Disable merging into combines"));
+
+namespace {
+
+class HexagonCopyToCombine : public MachineFunctionPass  {
+  const HexagonInstrInfo *TII;
+  const TargetRegisterInfo *TRI;
+public:
+  static char ID;
+
+  HexagonCopyToCombine() : MachineFunctionPass(ID) { }
+
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  const char *getPassName() const {
+    return "Hexagon Copy-To-Combine Pass";
+  }
+
+  virtual bool runOnMachineFunction(MachineFunction &Fn);
+
+private:
+  MachineInstr *findPairable(MachineInstr *I1, bool &DoInsertAtI1);
+
+  void combine(MachineInstr *I1, MachineInstr *I2,
+               MachineBasicBlock::iterator &MI, bool DoInsertAtI1);
+
+  bool isSafeToMoveTogether(MachineInstr *I1, MachineInstr *I2,
+                            unsigned I1DestReg, unsigned I2DestReg,
+                            bool &DoInsertAtI1);
+
+  void emitCombineRR(MachineBasicBlock::iterator &Before, unsigned DestReg,
+                     MachineOperand &HiOperand, MachineOperand &LoOperand);
+
+  void emitCombineRI(MachineBasicBlock::iterator &Before, unsigned DestReg,
+                     MachineOperand &HiOperand, MachineOperand &LoOperand);
+
+  void emitCombineIR(MachineBasicBlock::iterator &Before, unsigned DestReg,
+                     MachineOperand &HiOperand, MachineOperand &LoOperand);
+
+  void emitCombineII(MachineBasicBlock::iterator &Before, unsigned DestReg,
+                     MachineOperand &HiOperand, MachineOperand &LoOperand);
+};
+
+} // End anonymous namespace.
+
+char HexagonCopyToCombine::ID = 0;
+
+static bool isCombinableInstType(MachineInstr *MI,
+                                 const HexagonInstrInfo *TII) {
+  switch(MI->getOpcode()) {
+  case Hexagon::TFR: {
+    // A COPY instruction can be combined if its arguments are IntRegs (32bit).
+    assert(MI->getOperand(0).isReg() && MI->getOperand(1).isReg());
+
+    unsigned DestReg = MI->getOperand(0).getReg();
+    unsigned SrcReg = MI->getOperand(1).getReg();
+    return Hexagon::IntRegsRegClass.contains(DestReg) &&
+      Hexagon::IntRegsRegClass.contains(SrcReg);
+  }
+
+  case Hexagon::TFRI: {
+    // A transfer-immediate can be combined if its argument is a signed 8bit
+    // value.
+    assert(MI->getOperand(0).isReg() && MI->getOperand(1).isImm());
+    unsigned DestReg = MI->getOperand(0).getReg();
+    return Hexagon::IntRegsRegClass.contains(DestReg) &&
+      isInt<8>(MI->getOperand(1).getImm());
+  }
+  default:
+    break;
+  }
+
+  return false;
+}
+
+
+/// areCombinableOperations - Returns true if the two instruction can be merge
+/// into a combine (ignoring register constraints).
+static bool areCombinableOperations(const TargetRegisterInfo *TRI,
+                                    MachineInstr *I1, MachineInstr *I2) {
+  assert((I1->getOpcode() == Hexagon::TFR ||
+          I1->getOpcode() == Hexagon::TFRI) &&
+         (I2->getOpcode() == Hexagon::TFR ||
+          I2->getOpcode() == Hexagon::TFRI) &&
+         "Assume individual instructions are of a combinable type");
+
+  const HexagonRegisterInfo *QRI =
+    static_cast<const HexagonRegisterInfo *>(TRI);
+
+  // V4 added some combine variations (mixed immediate and register source
+  // operands), if we are on < V4 we can only combine 2 register-to-register
+  // moves and 2 immediate-to-register moves.
+  if (QRI->Subtarget.getHexagonArchVersion() < HexagonSubtarget::V4)
+    return I1->getOpcode() == I2->getOpcode();
+
+  return true;
+}
+
+static bool isEvenReg(unsigned Reg) {
+  assert(TargetRegisterInfo::isPhysicalRegister(Reg) &&
+         Hexagon::IntRegsRegClass.contains(Reg));
+  return (Reg - Hexagon::R0) % 2 == 0;
+}
+
+static void removeKillInfo(MachineInstr *MI, unsigned RegNotKilled) {
+  for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
+    MachineOperand &Op = MI->getOperand(I);
+    if (!Op.isReg() || Op.getReg() != RegNotKilled || !Op.isKill())
+      continue;
+    Op.setIsKill(false);
+  }
+}
+
+/// isUnsafeToMoveAccross - Returns true if it is unsafe to move a copy
+/// instruction from \p UseReg to \p DestReg over the instruction \p I.
+bool isUnsafeToMoveAccross(MachineInstr *I, unsigned UseReg, unsigned DestReg,
+                            const TargetRegisterInfo *TRI) {
+  return (UseReg && (I->modifiesRegister(UseReg, TRI))) ||
+          I->modifiesRegister(DestReg, TRI) ||
+          I->readsRegister(DestReg, TRI) ||
+          I->hasUnmodeledSideEffects() ||
+          I->isInlineAsm() || I->isDebugValue();
+}
+
+/// isSafeToMoveTogether - Returns true if it is safe to move I1 next to I2 such
+/// that the two instructions can be paired in a combine.
+bool HexagonCopyToCombine::isSafeToMoveTogether(MachineInstr *I1,
+                                                MachineInstr *I2,
+                                                unsigned I1DestReg,
+                                                unsigned I2DestReg,
+                                                bool &DoInsertAtI1) {
+  bool isSafe = true;
+
+  // First try to move I2 towards I1.
+  {
+    // A reverse_iterator instantiated like below starts before I2, and I1
+    // respectively.
+    // Look at instructions I in between I2 and (including) I1.
+    MachineBasicBlock::reverse_iterator I(I2),
+      End = MachineBasicBlock::reverse_iterator(I1);
+    bool IsImmUseReg = I2->getOperand(1).isImm();
+    unsigned I2UseReg = IsImmUseReg ? 0 : I2->getOperand(1).getReg();
+
+    // If I2 kills its operand and we move I2 over an instruction that also
+    // uses I2's use reg we need to modify that (first) instruction to now kill
+    // this reg.
+    unsigned KilledOperand = 0;
+    if (I2->killsRegister(I2UseReg))
+      KilledOperand = I2UseReg;
+    MachineInstr *KillingInstr = 0;
+
+    for (; I != End; ++I) {
+      // If the intervening instruction I:
+      //   * modifies I2's use reg
+      //   * modifies I2's def reg
+      //   * reads I2's def reg
+      //   * or has unmodelled side effects
+      // we can't move I2 across it.
+      if (isUnsafeToMoveAccross(&*I, I2UseReg, I2DestReg, TRI)) {
+        isSafe = false;
+        break;
+      }
+
+      // Update first use of the killed operand.
+      if (!KillingInstr && KilledOperand &&
+          I->readsRegister(KilledOperand, TRI))
+        KillingInstr = &*I;
+    }
+    if (isSafe) {
+      // Update the intermediate instruction to with the kill flag.
+      if (KillingInstr) {
+        bool Added = KillingInstr->addRegisterKilled(KilledOperand, TRI, true);
+        assert(Added && "Must successfully update kill flag");
+        removeKillInfo(I2, KilledOperand);
+      }
+      DoInsertAtI1 = true;
+      return true;
+    }
+  }
+
+  // Try to move I1 towards I2.
+  {
+    // Look at instructions I in between I1 and (including) I2.
+    MachineBasicBlock::iterator I(I1),
+      End(next(MachineBasicBlock::iterator(I2)));
+    bool IsImmUseReg = I1->getOperand(1).isImm();
+    unsigned I1UseReg = IsImmUseReg ? 0 : I1->getOperand(1).getReg();
+    // Track killed operands. If we move accross an instruction that kills our
+    // operand, we need to update the kill information on the moved I1. It kills
+    // the operand now.
+    MachineInstr *KillingInstr = 0;
+    unsigned KilledOperand = 0;
+
+    while(++I != End) {
+      // If the intervening instruction I:
+      //   * modifies I1's use reg
+      //   * modifies I1's def reg
+      //   * reads I1's def reg
+      //   * or has unmodelled side effects
+      //   We introduce this special case because llvm has no api to remove a
+      //   kill flag for a register (a removeRegisterKilled() analogous to
+      //   addRegisterKilled) that handles aliased register correctly.
+      //   * or has a killed aliased register use of I1's use reg
+      //           %D4<def> = TFRI64 16
+      //           %R6<def> = TFR %R9
+      //           %R8<def> = KILL %R8, %D4<imp-use,kill>
+      //      If we want to move R6 = across the KILL instruction we would have
+      //      to remove the %D4<imp-use,kill> operand. For now, we are
+      //      conservative and disallow the move.
+      // we can't move I1 across it.
+      if (isUnsafeToMoveAccross(I, I1UseReg, I1DestReg, TRI) ||
+          // Check for an aliased register kill. Bail out if we see one.
+          (!I->killsRegister(I1UseReg) && I->killsRegister(I1UseReg, TRI)))
+        return false;
+
+      // Check for an exact kill (registers match).
+      if (I1UseReg && I->killsRegister(I1UseReg)) {
+        assert(KillingInstr == 0 && "Should only see one killing instruction");
+        KilledOperand = I1UseReg;
+        KillingInstr = &*I;
+      }
+    }
+    if (KillingInstr) {
+      removeKillInfo(KillingInstr, KilledOperand);
+      // Update I1 to set the kill flag. This flag will later be picked up by
+      // the new COMBINE instruction.
+      bool Added = I1->addRegisterKilled(KilledOperand, TRI);
+      assert(Added && "Must successfully update kill flag");
+    }
+    DoInsertAtI1 = false;
+  }
+
+  return true;
+}
+
+bool HexagonCopyToCombine::runOnMachineFunction(MachineFunction &MF) {
+
+  if (IsCombinesDisabled) return false;
+
+  bool HasChanged = false;
+
+  // Get target info.
+  TRI = MF.getTarget().getRegisterInfo();
+  TII = static_cast<const HexagonInstrInfo *>(MF.getTarget().getInstrInfo());
+
+  // Traverse basic blocks.
+  for (MachineFunction::iterator BI = MF.begin(), BE = MF.end(); BI != BE;
+       ++BI) {
+    // Traverse instructions in basic block.
+    for(MachineBasicBlock::iterator MI = BI->begin(), End = BI->end();
+        MI != End;) {
+      MachineInstr *I1 = MI++;
+
+      // Ignore instructions that are not combinable.
+      if (!isCombinableInstType(I1, TII))
+        continue;
+
+      // Find a second instruction that can be merged into a combine
+      // instruction.
+      bool DoInsertAtI1 = false;
+      MachineInstr *I2 = findPairable(I1, DoInsertAtI1);
+      if (I2) {
+        HasChanged = true;
+        combine(I1, I2, MI, DoInsertAtI1);
+      }
+    }
+  }
+
+  return HasChanged;
+}
+
+/// findPairable - Returns an instruction that can be merged with \p I1 into a
+/// COMBINE instruction or 0 if no such instruction can be found. Returns true
+/// in \p DoInsertAtI1 if the combine must be inserted at instruction \p I1
+/// false if the combine must be inserted at the returned instruction.
+MachineInstr *HexagonCopyToCombine::findPairable(MachineInstr *I1,
+                                                 bool &DoInsertAtI1) {
+  MachineBasicBlock::iterator I2 = next(MachineBasicBlock::iterator(I1));
+  unsigned I1DestReg = I1->getOperand(0).getReg();
+
+  for (MachineBasicBlock::iterator End = I1->getParent()->end(); I2 != End;
+       ++I2) {
+    // Bail out early if we see a second definition of I1DestReg.
+    if (I2->modifiesRegister(I1DestReg, TRI))
+      break;
+
+    // Ignore non-combinable instructions.
+    if (!isCombinableInstType(I2, TII))
+      continue;
+
+    unsigned I2DestReg = I2->getOperand(0).getReg();
+
+    // Check that registers are adjacent and that the first destination register
+    // is even.
+    bool IsI1BeforeI2 = (I2DestReg - I1DestReg) == 1;
+    bool IsI2BeforeI1 = (I1DestReg - I2DestReg) == 1;
+    unsigned FirstRegIndex = IsI1BeforeI2 ? I1DestReg : I2DestReg;
+    if ((!IsI1BeforeI2 && !IsI2BeforeI1) || !isEvenReg(FirstRegIndex))
+      continue;
+
+    // Check that the two instructions are combinable. V4 allows more
+    // instructions to be merged into a combine.
+    if (!areCombinableOperations(TRI, I1, I2))
+      break;
+
+    if (isSafeToMoveTogether(I1, I2, I1DestReg, I2DestReg,
+                             DoInsertAtI1))
+      return I2;
+
+    // Not safe. Stop searching.
+    break;
+  }
+  return 0;
+}
+
+void HexagonCopyToCombine::combine(MachineInstr *I1, MachineInstr *I2,
+                                   MachineBasicBlock::iterator &MI,
+                                   bool DoInsertAtI1) {
+  // We are going to delete I2. If MI points to I2 advance it to the next
+  // instruction.
+  if ((MachineInstr *)MI == I2) ++MI;
+
+  // Figure out whether I1 or I2 goes into the lowreg part.
+  unsigned I1DestReg = I1->getOperand(0).getReg();
+  unsigned I2DestReg = I2->getOperand(0).getReg();
+  bool IsI1Loreg = (I2DestReg - I1DestReg) == 1;
+  unsigned LoRegDef = IsI1Loreg ? I1DestReg : I2DestReg;
+
+  // Get the double word register.
+  unsigned DoubleRegDest =
+    TRI->getMatchingSuperReg(LoRegDef, Hexagon::subreg_loreg,
+                             Hexagon::DoubleRegsRegisterClass);
+  assert(DoubleRegDest != 0 && "Expect a valid register");
+
+
+  // Setup source operands.
+  MachineOperand &LoOperand = IsI1Loreg ? I1->getOperand(1) :
+    I2->getOperand(1);
+  MachineOperand &HiOperand = IsI1Loreg ? I2->getOperand(1) :
+    I1->getOperand(1);
+
+  // Figure out which source is a register and which a constant.
+  bool IsHiReg = HiOperand.isReg();
+  bool IsLoReg = LoOperand.isReg();
+
+  MachineBasicBlock::iterator InsertPt(DoInsertAtI1 ? I1 : I2);
+  // Emit combine.
+  if (IsHiReg && IsLoReg)
+    emitCombineRR(InsertPt, DoubleRegDest, HiOperand, LoOperand);
+  else if (IsHiReg)
+    emitCombineRI(InsertPt, DoubleRegDest, HiOperand, LoOperand);
+  else if (IsLoReg)
+    emitCombineIR(InsertPt, DoubleRegDest, HiOperand, LoOperand);
+  else
+    emitCombineII(InsertPt, DoubleRegDest, HiOperand, LoOperand);
+
+  I1->eraseFromParent();
+  I2->eraseFromParent();
+}
+
+void HexagonCopyToCombine::emitCombineII(MachineBasicBlock::iterator &InsertPt,
+                                         unsigned DoubleDestReg,
+                                         MachineOperand &HiOperand,
+                                         MachineOperand &LoOperand) {
+  DebugLoc DL = InsertPt->getDebugLoc();
+  MachineBasicBlock *BB = InsertPt->getParent();
+
+  // Insert new combine instruction.
+  //  DoubleRegDest = combine #HiImm, #LoImm
+  BuildMI(*BB, InsertPt, DL, TII->get(Hexagon::COMBINE_ii), DoubleDestReg)
+    .addImm(HiOperand.getImm())
+    .addImm(LoOperand.getImm());
+}
+
+void HexagonCopyToCombine::emitCombineIR(MachineBasicBlock::iterator &InsertPt,
+                                         unsigned DoubleDestReg,
+                                         MachineOperand &HiOperand,
+                                         MachineOperand &LoOperand) {
+  unsigned LoReg = LoOperand.getReg();
+  unsigned LoRegKillFlag = getKillRegState(LoOperand.isKill());
+
+  DebugLoc DL = InsertPt->getDebugLoc();
+  MachineBasicBlock *BB = InsertPt->getParent();
+
+  // Insert new combine instruction.
+  //  DoubleRegDest = combine #HiImm, LoReg
+  BuildMI(*BB, InsertPt, DL, TII->get(Hexagon::COMBINE_ir_V4), DoubleDestReg)
+    .addImm(HiOperand.getImm())
+    .addReg(LoReg, LoRegKillFlag);
+}
+
+void HexagonCopyToCombine::emitCombineRI(MachineBasicBlock::iterator &InsertPt,
+                                         unsigned DoubleDestReg,
+                                         MachineOperand &HiOperand,
+                                         MachineOperand &LoOperand) {
+  unsigned HiRegKillFlag = getKillRegState(HiOperand.isKill());
+  unsigned HiReg = HiOperand.getReg();
+
+  DebugLoc DL = InsertPt->getDebugLoc();
+  MachineBasicBlock *BB = InsertPt->getParent();
+
+  // Insert new combine instruction.
+  //  DoubleRegDest = combine HiReg, #LoImm
+  BuildMI(*BB, InsertPt, DL, TII->get(Hexagon::COMBINE_ri_V4), DoubleDestReg)
+    .addReg(HiReg, HiRegKillFlag)
+    .addImm(LoOperand.getImm());
+}
+
+void HexagonCopyToCombine::emitCombineRR(MachineBasicBlock::iterator &InsertPt,
+                                         unsigned DoubleDestReg,
+                                         MachineOperand &HiOperand,
+                                         MachineOperand &LoOperand) {
+  unsigned LoRegKillFlag = getKillRegState(LoOperand.isKill());
+  unsigned HiRegKillFlag = getKillRegState(HiOperand.isKill());
+  unsigned LoReg = LoOperand.getReg();
+  unsigned HiReg = HiOperand.getReg();
+
+  DebugLoc DL = InsertPt->getDebugLoc();
+  MachineBasicBlock *BB = InsertPt->getParent();
+
+  // Insert new combine instruction.
+  //  DoubleRegDest = combine HiReg, LoReg
+  BuildMI(*BB, InsertPt, DL, TII->get(Hexagon::COMBINE_rr), DoubleDestReg)
+    .addReg(HiReg, HiRegKillFlag)
+    .addReg(LoReg, LoRegKillFlag);
+}
+
+FunctionPass *llvm::createHexagonCopyToCombine() {
+  return new HexagonCopyToCombine();
+}
+
diff --git a/lib/Target/Hexagon/HexagonInstrInfo.td b/lib/Target/Hexagon/HexagonInstrInfo.td
index fd5adef..cf7222a 100644
--- a/lib/Target/Hexagon/HexagonInstrInfo.td
+++ b/lib/Target/Hexagon/HexagonInstrInfo.td
@@ -246,6 +246,12 @@ def COMBINE_rr : ALU32_rr<(outs DoubleRegs:$dst),
             "$dst = combine($src1, $src2)",
             []>;
 
+let neverHasSideEffects = 1 in
+def COMBINE_ii : ALU32_ii<(outs DoubleRegs:$dst),
+            (ins s8Imm:$src1, s8Imm:$src2),
+            "$dst = combine(#$src1, #$src2)",
+            []>;
+
 // Mux.
 def VMUX_prr64 : ALU64_rr<(outs DoubleRegs:$dst), (ins PredRegs:$src1,
                                                    DoubleRegs:$src2,
diff --git a/lib/Target/Hexagon/HexagonTargetMachine.cpp b/lib/Target/Hexagon/HexagonTargetMachine.cpp
index 411325b..34036b2 100644
--- a/lib/Target/Hexagon/HexagonTargetMachine.cpp
+++ b/lib/Target/Hexagon/HexagonTargetMachine.cpp
@@ -122,6 +122,7 @@ bool HexagonPassConfig::addPostRegAlloc() {
 
 
 bool HexagonPassConfig::addPreSched2() {
+  PM.add(createHexagonCopyToCombine());
   addPass(IfConverterID);
   return true;
 }