lib/Target/Alpha/AlphaLLRP.cpp

   1 //===-- AlphaLLRP.cpp - Alpha Load Load Replay Trap elimination pass. -- --===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Here we check for potential replay traps introduced by the spiller
  11 // We also align some branch targets if we can do so for free.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #define DEBUG_TYPE "alpha-nops"
  16 #include "Alpha.h"
  17 #include "llvm/CodeGen/MachineFunctionPass.h"
  18 #include "llvm/CodeGen/MachineInstrBuilder.h"
  19 #include "llvm/Target/TargetMachine.h"
  20 #include "llvm/Target/TargetInstrInfo.h"
  21 #include "llvm/ADT/SetOperations.h"
  22 #include "llvm/ADT/Statistic.h"
  23 #include "llvm/Support/CommandLine.h"
  24 using namespace llvm;
  25
  26 STATISTIC(nopintro, "Number of nops inserted");
  27 STATISTIC(nopalign, "Number of nops inserted for alignment");
  28
  29 namespace {
  30   cl::opt<bool>
  31   AlignAll("alpha-align-all", cl::Hidden,
  32                    cl::desc("Align all blocks"));
  33
  34   struct AlphaLLRPPass : public MachineFunctionPass {
  35     /// Target machine description which we query for reg. names, data
  36     /// layout, etc.
  37     ///
  38     AlphaTargetMachine &TM;
  39
  40     static char ID;
  41     AlphaLLRPPass(AlphaTargetMachine &tm)
  42       : MachineFunctionPass(&ID), TM(tm) { }
  43
  44     virtual const char *getPassName() const {
  45       return "Alpha NOP inserter";
  46     }
  47
  48     bool runOnMachineFunction(MachineFunction &F) {
  49       const TargetInstrInfo *TII = F.getTarget().getInstrInfo();
  50       bool Changed = false;
  51       MachineInstr* prev[3] = {0,0,0};
  52       DebugLoc dl = DebugLoc::getUnknownLoc();
  53       unsigned count = 0;
  54       for (MachineFunction::iterator FI = F.begin(), FE = F.end();
  55            FI != FE; ++FI) {
  56         MachineBasicBlock& MBB = *FI;
  57         bool ub = false;
  58         for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ) {
  59           if (count%4 == 0)
  60             prev[0] = prev[1] = prev[2] = 0; //Slots cleared at fetch boundary
  61           ++count;
  62           MachineInstr *MI = I++;
  63           switch (MI->getOpcode()) {
  64           case Alpha::LDQ:  case Alpha::LDL:
  65           case Alpha::LDWU: case Alpha::LDBU:
  66           case Alpha::LDT: case Alpha::LDS:
  67           case Alpha::STQ:  case Alpha::STL:
  68           case Alpha::STW:  case Alpha::STB:
  69           case Alpha::STT: case Alpha::STS:
  70            if (MI->getOperand(2).getReg() == Alpha::R30) {
  71              if (prev[0] &&
  72                  prev[0]->getOperand(2).getReg() == MI->getOperand(2).getReg()&&
  73                  prev[0]->getOperand(1).getImm() == MI->getOperand(1).getImm()){
  74                prev[0] = prev[1];
  75                prev[1] = prev[2];
  76                prev[2] = 0;
  77                BuildMI(MBB, MI, dl, TII->get(Alpha::BISr), Alpha::R31)
  78                  .addReg(Alpha::R31)
  79                  .addReg(Alpha::R31);
  80                Changed = true; nopintro += 1;
  81                count += 1;
  82              } else if (prev[1]
  83                         && prev[1]->getOperand(2).getReg() ==
  84                         MI->getOperand(2).getReg()
  85                         && prev[1]->getOperand(1).getImm() ==
  86                         MI->getOperand(1).getImm()) {
  87                prev[0] = prev[2];
  88                prev[1] = prev[2] = 0;
  89                BuildMI(MBB, MI, dl, TII->get(Alpha::BISr), Alpha::R31)
  90                  .addReg(Alpha::R31)
  91                  .addReg(Alpha::R31);
  92                BuildMI(MBB, MI, dl, TII->get(Alpha::BISr), Alpha::R31)
  93                  .addReg(Alpha::R31)
  94                  .addReg(Alpha::R31);
  95                Changed = true; nopintro += 2;
  96                count += 2;
  97              } else if (prev[2]
  98                         && prev[2]->getOperand(2).getReg() ==
  99                         MI->getOperand(2).getReg()
 100                         && prev[2]->getOperand(1).getImm() ==
 101                         MI->getOperand(1).getImm()) {
 102                prev[0] = prev[1] = prev[2] = 0;
 103                BuildMI(MBB, MI, dl, TII->get(Alpha::BISr), Alpha::R31)
 104                  .addReg(Alpha::R31).addReg(Alpha::R31);
 105                BuildMI(MBB, MI, dl, TII->get(Alpha::BISr), Alpha::R31)
 106                  .addReg(Alpha::R31).addReg(Alpha::R31);
 107                BuildMI(MBB, MI, dl, TII->get(Alpha::BISr), Alpha::R31)
 108                  .addReg(Alpha::R31).addReg(Alpha::R31);
 109                Changed = true; nopintro += 3;
 110                count += 3;
 111              }
 112              prev[0] = prev[1];
 113              prev[1] = prev[2];
 114              prev[2] = MI;
 115              break;
 116            }
 117            prev[0] = prev[1];
 118            prev[1] = prev[2];
 119            prev[2] = 0;
 120            break;
 121           case Alpha::ALTENT:
 122           case Alpha::MEMLABEL:
 123           case Alpha::PCLABEL:
 124             --count;
 125             break;
 126           case Alpha::BR:
 127           case Alpha::JMP:
 128             ub = true;
 129             //fall through
 130           default:
 131             prev[0] = prev[1];
 132             prev[1] = prev[2];
 133             prev[2] = 0;
 134             break;
 135           }
 136         }
 137         if (ub || AlignAll) {
 138           //we can align stuff for free at this point
 139           while (count % 4) {
 140             BuildMI(MBB, MBB.end(), dl, TII->get(Alpha::BISr), Alpha::R31)
 141               .addReg(Alpha::R31).addReg(Alpha::R31);
 142             ++count;
 143             ++nopalign;
 144             prev[0] = prev[1];
 145             prev[1] = prev[2];
 146             prev[2] = 0;
 147           }
 148         }
 149       }
 150       return Changed;
 151     }
 152   };
 153   char AlphaLLRPPass::ID = 0;
 154 } // end of anonymous namespace
 155
 156 FunctionPass *llvm::createAlphaLLRPPass(AlphaTargetMachine &tm) {
 157   return new AlphaLLRPPass(tm);
 158 }