lib/Target/Mips/MipsDelaySlotFiller.cpp

   1 //===-- DelaySlotFiller.cpp - Mips delay slot filler ---------------------===//
   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 // Simple pass to fills delay slots with NOPs.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #define DEBUG_TYPE "delay-slot-filler"
  15
  16 #include "Mips.h"
  17 #include "MipsTargetMachine.h"
  18 #include "llvm/CodeGen/MachineFunctionPass.h"
  19 #include "llvm/CodeGen/MachineInstrBuilder.h"
  20 #include "llvm/Target/TargetInstrInfo.h"
  21 #include "llvm/ADT/Statistic.h"
  22
  23 using namespace llvm;
  24
  25 STATISTIC(FilledSlots, "Number of delay slots filled");
  26
  27 namespace {
  28   struct Filler : public MachineFunctionPass {
  29
  30     TargetMachine &TM;
  31     const TargetInstrInfo *TII;
  32
  33     static char ID;
  34     Filler(TargetMachine &tm)
  35       : MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()) { }
  36
  37     virtual const char *getPassName() const {
  38       return "Mips Delay Slot Filler";
  39     }
  40
  41     bool runOnMachineBasicBlock(MachineBasicBlock &MBB);
  42     bool runOnMachineFunction(MachineFunction &F) {
  43       bool Changed = false;
  44       for (MachineFunction::iterator FI = F.begin(), FE = F.end();
  45            FI != FE; ++FI)
  46         Changed |= runOnMachineBasicBlock(*FI);
  47       return Changed;
  48     }
  49
  50   };
  51   char Filler::ID = 0;
  52 } // end of anonymous namespace
  53
  54 /// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
  55 /// Currently, we fill delay slots with NOPs. We assume there is only one
  56 /// delay slot per delayed instruction.
  57 bool Filler::
  58 runOnMachineBasicBlock(MachineBasicBlock &MBB)
  59 {
  60   bool Changed = false;
  61   for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
  62     const MCInstrDesc& MCid = I->getDesc();
  63     if (MCid.hasDelaySlot() &&
  64         (TM.getSubtarget<MipsSubtarget>().isMips1() ||
  65          MCid.isCall() || MCid.isBranch() || MCid.isReturn())) {
  66       MachineBasicBlock::iterator J = I;
  67       ++J;
  68       BuildMI(MBB, J, I->getDebugLoc(), TII->get(Mips::NOP));
  69       ++FilledSlots;
  70       Changed = true;
  71     }
  72   }
  73
  74   return Changed;
  75 }
  76
  77 /// createMipsDelaySlotFillerPass - Returns a pass that fills in delay
  78 /// slots in Mips MachineFunctions
  79 FunctionPass *llvm::createMipsDelaySlotFillerPass(MipsTargetMachine &tm) {
  80   return new Filler(tm);
  81 }
  82