Vendor import of llvm tags/RELEASE_33/final r183502 (effectively, 3.3vendor/llvm/llvm-release_33-r183502

release):
http://llvm.org/svn/llvm-project/llvm/tags/RELEASE_33/final@183502

1 files changed, 253 insertions, 0 deletions

diff --git a/lib/Target/X86/X86FixupLEAs.cpp b/lib/Target/X86/X86FixupLEAs.cpp
new file mode 100644
index 000000000000..0dd034c45098
--- /dev/null
+++ b/lib/Target/X86/X86FixupLEAs.cpp
@@ -0,0 +1,253 @@
+//===-- X86FixupLEAs.cpp - use or replace LEA instructions -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the pass which will find  instructions  which
+// can be re-written as LEA instructions in order to reduce pipeline
+// delays for some models of the Intel Atom family.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "x86-fixup-LEAs"
+#include "X86.h"
+#include "X86InstrInfo.h"
+#include "X86Subtarget.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrInfo.h"
+using namespace llvm;
+
+STATISTIC(NumLEAs, "Number of LEA instructions created");
+
+namespace {
+  class FixupLEAPass : public MachineFunctionPass {
+    enum RegUsageState { RU_NotUsed, RU_Write, RU_Read };
+    static char ID;
+    /// \brief Loop over all of the instructions in the basic block
+    /// replacing applicable instructions with LEA instructions,
+    /// where appropriate.
+    bool processBasicBlock(MachineFunction &MF, MachineFunction::iterator MFI);
+
+    virtual const char *getPassName() const { return "X86 Atom LEA Fixup";}
+
+    /// \brief Given a machine register, look for the instruction
+    /// which writes it in the current basic block. If found,
+    /// try to replace it with an equivalent LEA instruction.
+    /// If replacement succeeds, then also process the the newly created
+    /// instruction.
+    void  seekLEAFixup(MachineOperand& p, MachineBasicBlock::iterator& I,
+                      MachineFunction::iterator MFI);
+
+    /// \brief Given a memory access or LEA instruction
+    /// whose address mode uses a base and/or index register, look for
+    /// an opportunity to replace the instruction which sets the base or index
+    /// register with an equivalent LEA instruction.
+    void processInstruction(MachineBasicBlock::iterator& I,
+                            MachineFunction::iterator MFI);
+
+    /// \brief Determine if an instruction references a machine register
+    /// and, if so, whether it reads or writes the register.
+    RegUsageState usesRegister(MachineOperand& p,
+                               MachineBasicBlock::iterator I);
+
+    /// \brief Step backwards through a basic block, looking
+    /// for an instruction which writes a register within 
+    /// a maximum of INSTR_DISTANCE_THRESHOLD instruction latency cycles.
+    MachineBasicBlock::iterator searchBackwards(MachineOperand& p,
+                                                MachineBasicBlock::iterator& I,
+                                                MachineFunction::iterator MFI);
+
+    /// \brief if an instruction can be converted to an 
+    /// equivalent LEA, insert the new instruction into the basic block
+    /// and return a pointer to it. Otherwise, return zero.
+    MachineInstr* postRAConvertToLEA(MachineFunction::iterator &MFI,
+                                     MachineBasicBlock::iterator &MBBI) const;
+
+  public:
+    FixupLEAPass() : MachineFunctionPass(ID) {}
+
+    /// \brief Loop over all of the basic blocks,
+    /// replacing instructions by equivalent LEA instructions
+    /// if needed and when possible.
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+
+  private:
+    MachineFunction *MF;
+    const TargetMachine *TM;
+    const TargetInstrInfo *TII; // Machine instruction info.
+
+  };
+  char FixupLEAPass::ID = 0;
+}
+
+MachineInstr *
+FixupLEAPass::postRAConvertToLEA(MachineFunction::iterator &MFI,
+                                 MachineBasicBlock::iterator &MBBI) const {
+  MachineInstr* MI = MBBI;
+  MachineInstr* NewMI;
+  switch (MI->getOpcode()) {
+  case X86::MOV32rr: 
+  case X86::MOV64rr: {
+    const MachineOperand& Src = MI->getOperand(1);
+    const MachineOperand& Dest = MI->getOperand(0);
+    NewMI = BuildMI(*MF, MI->getDebugLoc(),
+      TII->get( MI->getOpcode() == X86::MOV32rr ? X86::LEA32r : X86::LEA64r))
+      .addOperand(Dest)
+      .addOperand(Src).addImm(1).addReg(0).addImm(0).addReg(0);
+    MFI->insert(MBBI, NewMI);   // Insert the new inst
+    return NewMI;
+  }
+  case X86::ADD64ri32:
+  case X86::ADD64ri8:
+  case X86::ADD64ri32_DB:
+  case X86::ADD64ri8_DB:
+  case X86::ADD32ri:
+  case X86::ADD32ri8:
+  case X86::ADD32ri_DB:
+  case X86::ADD32ri8_DB:
+  case X86::ADD16ri:
+  case X86::ADD16ri8:
+  case X86::ADD16ri_DB:
+  case X86::ADD16ri8_DB:
+    if (!MI->getOperand(2).isImm()) {
+      // convertToThreeAddress will call getImm()
+      // which requires isImm() to be true
+      return 0;
+    }
+  }
+  return TII->convertToThreeAddress(MFI, MBBI, 0);
+}
+
+FunctionPass *llvm::createX86FixupLEAs() {
+  return new FixupLEAPass();
+}
+
+bool FixupLEAPass::runOnMachineFunction(MachineFunction &Func) {
+  MF = &Func;
+  TII = Func.getTarget().getInstrInfo();
+  TM = &MF->getTarget();
+
+  DEBUG(dbgs() << "Start X86FixupLEAs\n";);
+  // Process all basic blocks.
+  for (MachineFunction::iterator I = Func.begin(), E = Func.end(); I != E; ++I)
+    processBasicBlock(Func, I);
+  DEBUG(dbgs() << "End X86FixupLEAs\n";);
+
+  return true;
+}
+
+FixupLEAPass::RegUsageState FixupLEAPass::usesRegister(MachineOperand& p,
+                                MachineBasicBlock::iterator I) {
+  RegUsageState RegUsage = RU_NotUsed;
+  MachineInstr* MI = I;
+
+  for (unsigned int i = 0; i < MI->getNumOperands(); ++i) {
+    MachineOperand& opnd = MI->getOperand(i);
+    if (opnd.isReg() && opnd.getReg() == p.getReg()){
+      if (opnd.isDef())
+        return RU_Write;
+      RegUsage = RU_Read;
+    }
+  }
+  return RegUsage;
+}
+
+/// getPreviousInstr - Given a reference to an instruction in a basic
+/// block, return a reference to the previous instruction in the block,
+/// wrapping around to the last instruction of the block if the block
+/// branches to itself.
+static inline bool getPreviousInstr(MachineBasicBlock::iterator& I,
+                                    MachineFunction::iterator MFI) {
+  if (I == MFI->begin()) {
+    if (MFI->isPredecessor(MFI)) {
+      I = --MFI->end();
+      return true;
+    }
+    else
+      return false;
+  }
+  --I;
+  return true;
+}
+
+MachineBasicBlock::iterator FixupLEAPass::searchBackwards(MachineOperand& p,
+                                   MachineBasicBlock::iterator& I,
+                                   MachineFunction::iterator MFI) {
+  int InstrDistance = 1;
+  MachineBasicBlock::iterator CurInst;
+  static const int INSTR_DISTANCE_THRESHOLD = 5;
+
+  CurInst = I;
+  bool Found;
+  Found = getPreviousInstr(CurInst, MFI);
+  while( Found && I != CurInst) {
+    if (CurInst->isCall() || CurInst->isInlineAsm())
+      break;
+    if (InstrDistance > INSTR_DISTANCE_THRESHOLD)
+      break; // too far back to make a difference
+    if (usesRegister(p, CurInst) == RU_Write){
+      return CurInst;
+    }
+    InstrDistance += TII->getInstrLatency(TM->getInstrItineraryData(), CurInst);
+    Found = getPreviousInstr(CurInst, MFI);
+  }
+  return 0;
+}
+
+void FixupLEAPass::processInstruction(MachineBasicBlock::iterator& I,
+                                      MachineFunction::iterator MFI) {
+  // Process a load, store, or LEA instruction.
+  MachineInstr *MI = I;
+  int opcode = MI->getOpcode();
+  const MCInstrDesc& Desc = MI->getDesc();
+  int AddrOffset = X86II::getMemoryOperandNo(Desc.TSFlags, opcode);
+  if (AddrOffset >= 0) {
+    AddrOffset += X86II::getOperandBias(Desc);
+    MachineOperand& p = MI->getOperand(AddrOffset + X86::AddrBaseReg);
+    if (p.isReg() && p.getReg() != X86::ESP) {
+      seekLEAFixup(p, I, MFI);
+    }
+    MachineOperand& q = MI->getOperand(AddrOffset + X86::AddrIndexReg);
+    if (q.isReg() && q.getReg() != X86::ESP) {
+      seekLEAFixup(q, I, MFI);
+    }
+  }
+}
+
+void FixupLEAPass::seekLEAFixup(MachineOperand& p,
+                                MachineBasicBlock::iterator& I,
+                                MachineFunction::iterator MFI) {
+  MachineBasicBlock::iterator MBI = searchBackwards(p, I, MFI);
+  if (MBI) {
+    MachineInstr* NewMI = postRAConvertToLEA(MFI, MBI);
+    if (NewMI) {
+      ++NumLEAs;
+      DEBUG(dbgs() << "Candidate to replace:"; MBI->dump(););
+      // now to replace with an equivalent LEA...
+      DEBUG(dbgs() << "Replaced by: "; NewMI->dump(););
+      MFI->erase(MBI);
+      MachineBasicBlock::iterator J =
+                             static_cast<MachineBasicBlock::iterator> (NewMI);
+      processInstruction(J, MFI);
+    }
+  }
+}
+
+bool FixupLEAPass::processBasicBlock(MachineFunction &MF,
+                                     MachineFunction::iterator MFI) {
+
+  for (MachineBasicBlock::iterator I = MFI->begin(); I != MFI->end(); ++I)
+    processInstruction(I, MFI);
+  return false;
+}