lib/CodeGen/ExpandISelPseudos.cpp

   1 //===-- llvm/CodeGen/ExpandISelPseudos.cpp ----------------------*- C++ -*-===//
   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 // Expand Pseudo-instructions produced by ISel. These are usually to allow
  11 // the expansion to contain control flow, such as a conditional move
  12 // implemented with a conditional branch and a phi, or an atomic operation
  13 // implemented with a loop.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #define DEBUG_TYPE "expand-isel-pseudos"
  18 #include "llvm/CodeGen/MachineFunction.h"
  19 #include "llvm/CodeGen/MachineFunctionPass.h"
  20 #include "llvm/CodeGen/Passes.h"
  21 #include "llvm/Target/TargetLowering.h"
  22 #include "llvm/Target/TargetMachine.h"
  23 #include "llvm/Support/Debug.h"
  24 using namespace llvm;
  25
  26 namespace {
  27   class ExpandISelPseudos : public MachineFunctionPass {
  28   public:
  29     static char ID; // Pass identification, replacement for typeid
  30     ExpandISelPseudos() : MachineFunctionPass(ID) {}
  31
  32   private:
  33     virtual bool runOnMachineFunction(MachineFunction &MF);
  34
  35     const char *getPassName() const {
  36       return "Expand ISel Pseudo-instructions";
  37     }
  38
  39     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  40       MachineFunctionPass::getAnalysisUsage(AU);
  41     }
  42   };
  43 } // end anonymous namespace
  44
  45 char ExpandISelPseudos::ID = 0;
  46 INITIALIZE_PASS(ExpandISelPseudos, "expand-isel-pseudos",
  47                 "Expand CodeGen Pseudo-instructions", false, false)
  48
  49 FunctionPass *llvm::createExpandISelPseudosPass() {
  50   return new ExpandISelPseudos();
  51 }
  52
  53 bool ExpandISelPseudos::runOnMachineFunction(MachineFunction &MF) {
  54   bool Changed = false;
  55   const TargetLowering *TLI = MF.getTarget().getTargetLowering();
  56
  57   // Iterate through each instruction in the function, looking for pseudos.
  58   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
  59     MachineBasicBlock *MBB = I;
  60     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
  61          MBBI != MBBE; ) {
  62       MachineInstr *MI = MBBI++;
  63
  64       // If MI is a pseudo, expand it.
  65       const MCInstrDesc &MCID = MI->getDesc();
  66       if (MCID.usesCustomInsertionHook()) {
  67         Changed = true;
  68         MachineBasicBlock *NewMBB =
  69           TLI->EmitInstrWithCustomInserter(MI, MBB);
  70         // The expansion may involve new basic blocks.
  71         if (NewMBB != MBB) {
  72           MBB = NewMBB;
  73           I = NewMBB;
  74           MBBI = NewMBB->begin();
  75           MBBE = NewMBB->end();
  76         }
  77       }
  78     }
  79   }
  80
  81   return Changed;
  82 }