MipsDelaySlotFiller.cpp revision 224145 
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
23using namespace llvm;
24
25STATISTIC(FilledSlots, "Number of delay slots filled");
26
27namespace {
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.
57bool Filler::
58runOnMachineBasicBlock(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
79FunctionPass *llvm::createMipsDelaySlotFillerPass(MipsTargetMachine &tm) {
80  return new Filler(tm);
81}
82
83