lib/Target/PIC16/PIC16MemSelOpt.cpp

   1 //===-- PIC16MemSelOpt.cpp - PIC16 banksel optimizer  --------------------===//
   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 file defines the pass which optimizes the emitting of banksel
  11 // instructions before accessing data memory. This currently works within
  12 // a basic block only and keep tracks of the last accessed memory bank.
  13 // If memory access continues to be in the same bank it just makes banksel
  14 // immediate, which is a part of the insn accessing the data memory, from 1
  15 // to zero. The asm printer emits a banksel only if that immediate is 1.
  16 //
  17 // FIXME: this is not implemented yet.  The banksel pass only works on local
  18 // basic blocks.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #define DEBUG_TYPE "pic16-codegen"
  23 #include "PIC16.h"
  24 #include "PIC16InstrInfo.h"
  25 #include "PIC16TargetAsmInfo.h"
  26 #include "PIC16TargetMachine.h"
  27 #include "llvm/CodeGen/MachineFunctionPass.h"
  28 #include "llvm/CodeGen/MachineInstrBuilder.h"
  29 #include "llvm/CodeGen/Passes.h"
  30 #include "llvm/Target/TargetInstrInfo.h"
  31 #include "llvm/Target/TargetMachine.h"
  32 #include "llvm/GlobalValue.h"
  33 #include "llvm/DerivedTypes.h"
  34 #include "llvm/Support/Compiler.h"
  35
  36 using namespace llvm;
  37
  38 namespace {
  39   struct VISIBILITY_HIDDEN MemSelOpt : public MachineFunctionPass {
  40     static char ID;
  41     MemSelOpt() : MachineFunctionPass(&ID) {}
  42
  43     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  44       AU.addPreservedID(MachineLoopInfoID);
  45       AU.addPreservedID(MachineDominatorsID);
  46       MachineFunctionPass::getAnalysisUsage(AU);
  47     }
  48
  49     virtual bool runOnMachineFunction(MachineFunction &MF);
  50
  51     virtual const char *getPassName() const {
  52       return "PIC16 Memsel Optimizer";
  53     }
  54
  55    bool processBasicBlock(MachineFunction &MF, MachineBasicBlock &MBB);
  56    bool processInstruction(MachineInstr *MI);
  57
  58   private:
  59     const TargetInstrInfo *TII; // Machine instruction info.
  60     MachineBasicBlock *MBB;     // Current basic block
  61     std::string CurBank;
  62
  63   };
  64   char MemSelOpt::ID = 0;
  65 }
  66
  67 FunctionPass *llvm::createPIC16MemSelOptimizerPass() {
  68   return new MemSelOpt();
  69 }
  70
  71
  72 /// runOnMachineFunction - Loop over all of the basic blocks, transforming FP
  73 /// register references into FP stack references.
  74 ///
  75 bool MemSelOpt::runOnMachineFunction(MachineFunction &MF) {
  76   TII = MF.getTarget().getInstrInfo();
  77   bool Changed = false;
  78   for (MachineFunction::iterator I = MF.begin(), E = MF.end();
  79        I != E; ++I) {
  80     Changed |= processBasicBlock(MF, *I);
  81   }
  82
  83   return Changed;
  84 }
  85
  86 /// processBasicBlock - Loop over all of the instructions in the basic block,
  87 /// transforming FP instructions into their stack form.
  88 ///
  89 bool MemSelOpt::processBasicBlock(MachineFunction &MF, MachineBasicBlock &BB) {
  90   bool Changed = false;
  91   MBB = &BB;
  92
  93   // Let us assume that when entering a basic block now bank is selected.
  94   // Ideally we should look at the predecessors for this information.
  95   CurBank="";
  96
  97   for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) {
  98     Changed |= processInstruction(I);
  99   }
 100   return Changed;
 101 }
 102
 103 bool MemSelOpt::processInstruction(MachineInstr *MI) {
 104   bool Changed = false;
 105
 106   unsigned NumOperands = MI->getNumOperands();
 107   if (NumOperands == 0) return false;
 108
 109
 110   // If this insn is not going to access any memory, return.
 111   const TargetInstrDesc &TID = TII->get(MI->getOpcode());
 112   if (! (TID.isCall() || TID.mayLoad() || TID.mayStore()))
 113     return false;
 114
 115   // Scan for the memory address operand.
 116   // FIXME: Should we use standard interfaces like memoperands_iterator,
 117   // hasMemOperand() etc ?
 118   int MemOpPos = -1;
 119   for (unsigned i = 0; i < NumOperands; i++) {
 120     MachineOperand Op = MI->getOperand(i);
 121     if (Op.getType() ==  MachineOperand::MO_GlobalAddress ||
 122         Op.getType() ==  MachineOperand::MO_ExternalSymbol) {
 123       // We found one mem operand. Next one should be BS.
 124       MemOpPos = i;
 125       break;
 126     }
 127   }
 128
 129   // If we did not find an insn accessing memory. Continue.
 130   if (MemOpPos == -1) return Changed;
 131
 132   // Get the MemOp.
 133   MachineOperand &Op = MI->getOperand(MemOpPos);
 134
 135   // If this is a pagesel material, handle it first.
 136   if (MI->getOpcode() == PIC16::CALL) {
 137     DebugLoc dl = MI->getDebugLoc();
 138     BuildMI(*MBB, MI, dl, TII->get(PIC16::pagesel)).
 139       addOperand(Op);
 140     return true;
 141   }
 142
 143   // Get the section name(NewBank) for MemOp.
 144   // This assumes that the section names for globals are laready set by
 145   // AsmPrinter->doInitialization.
 146   std::string NewBank = CurBank;
 147   if (Op.getType() ==  MachineOperand::MO_GlobalAddress &&
 148       Op.getGlobal()->getType()->getAddressSpace() == PIC16ISD::RAM_SPACE) {
 149     NewBank = Op.getGlobal()->getSection();
 150   } else if (Op.getType() ==  MachineOperand::MO_ExternalSymbol) {
 151     // External Symbol is generated for temp data and arguments. They are
 152     // in fpdata.<functionname>.# section.
 153     std::string Sym = Op.getSymbolName();
 154     NewBank = PAN::getSectionNameForSym(Sym);
 155   }
 156
 157   // If the previous and new section names are same, we don't need to
 158   // emit banksel.
 159   if (NewBank.compare(CurBank) != 0 ) {
 160     DebugLoc dl = MI->getDebugLoc();
 161     BuildMI(*MBB, MI, dl, TII->get(PIC16::banksel)).
 162       addOperand(Op);
 163     Changed = true;
 164     CurBank = NewBank;
 165   }
 166
 167   return Changed;
 168 }
 169