1 //===-- DelaySlotFiller.cpp - SPARC 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 // This is a simple local pass that fills delay slots with NOPs.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #define DEBUG_TYPE "delayslotfiller"
15 #include "Sparc.h"
16 #include "llvm/CodeGen/MachineFunctionPass.h"
17 #include "llvm/CodeGen/MachineInstrBuilder.h"
18 #include "llvm/Target/TargetMachine.h"
19 #include "llvm/Target/TargetInstrInfo.h"
20 #include "llvm/ADT/Statistic.h"
21 using namespace llvm;
22 
23 STATISTIC(FilledSlots, "Number of delay slots filled");
24 
25 namespace {
26   struct Filler : public MachineFunctionPass {
27     /// Target machine description which we query for reg. names, data
28     /// layout, etc.
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 "SPARC 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 /// createSparcDelaySlotFillerPass - Returns a pass that fills in delay
55 /// slots in Sparc MachineFunctions
56 ///
57 FunctionPass *llvm::createSparcDelaySlotFillerPass(TargetMachine &tm) {
58   return new Filler(tm);
59 }
60 
61 /// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
62 /// Currently, we fill delay slots with NOPs. We assume there is only one
63 /// delay slot per delayed instruction.
64 ///
65 bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
66   bool Changed = false;
67   for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
68     if (I->getDesc().hasDelaySlot()) {
69       MachineBasicBlock::iterator J = I;
70       ++J;
71       BuildMI(MBB, J, DebugLoc::getUnknownLoc(), TII->get(SP::NOP));
72       ++FilledSlots;
73       Changed = true;
74     }
75   return Changed;
76 }
77