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 #include "llvm/CodeGen/MachineFunction.h"
  18 #include "llvm/CodeGen/MachineFunctionPass.h"
  19 #include "llvm/CodeGen/Passes.h"
  20 #include "llvm/CodeGen/TargetLowering.h"
  21 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  22 #include "llvm/Support/Debug.h"
  23 using namespace llvm;
  24
  25 #define DEBUG_TYPE "expand-isel-pseudos"
  26
  27 namespace {
  28   class ExpandISelPseudos : public MachineFunctionPass {
  29   public:
  30     static char ID; // Pass identification, replacement for typeid
  31     ExpandISelPseudos() : MachineFunctionPass(ID) {}
  32
  33   private:
  34     bool runOnMachineFunction(MachineFunction &MF) override;
  35
  36     void getAnalysisUsage(AnalysisUsage &AU) const override {
  37       MachineFunctionPass::getAnalysisUsage(AU);
  38     }
  39   };
  40 } // end anonymous namespace
  41
  42 char ExpandISelPseudos::ID = 0;
  43 char &llvm::ExpandISelPseudosID = ExpandISelPseudos::ID;
  44 INITIALIZE_PASS(ExpandISelPseudos, DEBUG_TYPE,
  45                 "Expand ISel Pseudo-instructions", false, false)
  46
  47 bool ExpandISelPseudos::runOnMachineFunction(MachineFunction &MF) {
  48   bool Changed = false;
  49   const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
  50
  51   // Iterate through each instruction in the function, looking for pseudos.
  52   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
  53     MachineBasicBlock *MBB = &*I;
  54     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
  55          MBBI != MBBE; ) {
  56       MachineInstr &MI = *MBBI++;
  57
  58       // If MI is a pseudo, expand it.
  59       if (MI.usesCustomInsertionHook()) {
  60         Changed = true;
  61         MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
  62         // The expansion may involve new basic blocks.
  63         if (NewMBB != MBB) {
  64           MBB = NewMBB;
  65           I = NewMBB->getIterator();
  66           MBBI = NewMBB->begin();
  67           MBBE = NewMBB->end();
  68         }
  69       }
  70     }
  71   }
  72
  73   return Changed;
  74 }