lib/Target/CellSPU/SPUNopFiller.cpp

   1 //===-- SPUNopFiller.cpp - Add nops/lnops to align the pipelines---===//
   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 // The final pass just before assembly printing. This pass is the last
  11 // checkpoint where nops and lnops are added to the instruction stream to
  12 // satisfy the dual issue requirements. The actual dual issue scheduling is
  13 // done (TODO: nowhere, currently)
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "SPU.h"
  18 #include "SPUTargetMachine.h"
  19 #include "llvm/CodeGen/MachineFunctionPass.h"
  20 #include "llvm/CodeGen/MachineInstrBuilder.h"
  21 #include "llvm/Target/TargetInstrInfo.h"
  22 #include "llvm/Support/Debug.h"
  23 #include "llvm/Support/raw_ostream.h"
  24
  25 using namespace llvm;
  26
  27 namespace {
  28   struct SPUNopFiller : public MachineFunctionPass {
  29
  30     TargetMachine &TM;
  31     const TargetInstrInfo *TII;
  32     const InstrItineraryData *IID;
  33     bool isEvenPlace;  // the instruction slot (mem address) at hand is even/odd
  34
  35     static char ID;
  36     SPUNopFiller(TargetMachine &tm)
  37       : MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()),
  38         IID(tm.getInstrItineraryData())
  39     {
  40       DEBUG( dbgs() << "********** SPU Nop filler **********\n" ; );
  41     }
  42
  43     virtual const char *getPassName() const {
  44       return "SPU nop/lnop Filler";
  45     }
  46
  47     void runOnMachineBasicBlock(MachineBasicBlock &MBB);
  48
  49     bool runOnMachineFunction(MachineFunction &F) {
  50       isEvenPlace = true; //all functions get an .align 3 directive at start
  51       for (MachineFunction::iterator FI = F.begin(), FE = F.end();
  52            FI != FE; ++FI)
  53         runOnMachineBasicBlock(*FI);
  54       return true; //never-ever do any more modifications, just print it!
  55     }
  56
  57     typedef enum { none   = 0, // no more instructions in this function / BB
  58                    pseudo = 1, // this does not get executed
  59                    even   = 2,
  60                    odd    = 3 } SPUOpPlace;
  61     SPUOpPlace getOpPlacement( MachineInstr &instr );
  62
  63   };
  64   char SPUNopFiller::ID = 0;
  65
  66 }
  67
  68 // Fill a BasicBlock to alignment.
  69 // In the assebly we align the functions to 'even' adresses, but
  70 // basic blocks have an implicit alignmnet. We hereby define
  71 // basic blocks to have the same, even, alignment.
  72 void SPUNopFiller::
  73 runOnMachineBasicBlock(MachineBasicBlock &MBB)
  74 {
  75   assert( isEvenPlace && "basic block start from odd address");
  76   for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
  77   {
  78     SPUOpPlace this_optype, next_optype;
  79     MachineBasicBlock::iterator J = I;
  80     J++;
  81
  82     this_optype = getOpPlacement( *I );
  83     next_optype = none;
  84     while (J!=MBB.end()){
  85       next_optype = getOpPlacement( *J );
  86       ++J;
  87       if (next_optype != pseudo )
  88         break;
  89     }
  90
  91     // padd: odd(wrong), even(wrong), ...
  92     // to:   nop(corr), odd(corr), even(corr)...
  93     if( isEvenPlace && this_optype == odd && next_optype == even ) {
  94       DEBUG( dbgs() <<"Adding NOP before: "; );
  95       DEBUG( I->dump(); );
  96       BuildMI(MBB, I, I->getDebugLoc(), TII->get(SPU::ENOP));
  97       isEvenPlace=false;
  98     }
  99
 100     // padd: even(wrong), odd(wrong), ...
 101     // to:   lnop(corr), even(corr), odd(corr)...
 102     else if ( !isEvenPlace && this_optype == even && next_optype == odd){
 103       DEBUG( dbgs() <<"Adding LNOP before: "; );
 104       DEBUG( I->dump(); );
 105       BuildMI(MBB, I, I->getDebugLoc(), TII->get(SPU::LNOP));
 106       isEvenPlace=true;
 107     }
 108
 109     // now go to next mem slot
 110     if( this_optype != pseudo )
 111       isEvenPlace = !isEvenPlace;
 112
 113   }
 114
 115   // padd basicblock end
 116   if( !isEvenPlace ){
 117     MachineBasicBlock::iterator J = MBB.end();
 118     J--;
 119     if (getOpPlacement( *J ) == odd) {
 120       DEBUG( dbgs() <<"Padding basic block with NOP\n"; );
 121       BuildMI(MBB, J, J->getDebugLoc(), TII->get(SPU::ENOP));
 122     }
 123     else {
 124       J++;
 125       DEBUG( dbgs() <<"Padding basic block with LNOP\n"; );
 126       BuildMI(MBB, J, DebugLoc(), TII->get(SPU::LNOP));
 127     }
 128     isEvenPlace=true;
 129   }
 130 }
 131
 132 FunctionPass *llvm::createSPUNopFillerPass(SPUTargetMachine &tm) {
 133   return new SPUNopFiller(tm);
 134 }
 135
 136 // Figure out if 'instr' is executed in the even or odd pipeline
 137 SPUNopFiller::SPUOpPlace
 138 SPUNopFiller::getOpPlacement( MachineInstr &instr ) {
 139   int sc = instr.getDesc().getSchedClass();
 140   const InstrStage *stage = IID->beginStage(sc);
 141   unsigned FUs = stage->getUnits();
 142   SPUOpPlace retval;
 143
 144   switch( FUs ) {
 145     case 0: retval = pseudo; break;
 146     case 1: retval = odd;    break;
 147     case 2: retval = even;   break;
 148     default: retval= pseudo;
 149              assert( false && "got unknown FuncUnit\n");
 150              break;
 151   };
 152   return retval;
 153 }