ExpandISelPseudos.cpp revision 1dd8c8560d45d36a8e507cd014352f1d313f9f9e 
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"
24using namespace llvm;
25
26namespace {
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    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
36      MachineFunctionPass::getAnalysisUsage(AU);
37    }
38  };
39} // end anonymous namespace
40
41char ExpandISelPseudos::ID = 0;
42char &llvm::ExpandISelPseudosID = ExpandISelPseudos::ID;
43INITIALIZE_PASS(ExpandISelPseudos, "expand-isel-pseudos",
44                "Expand ISel Pseudo-instructions", false, false)
45
46bool ExpandISelPseudos::runOnMachineFunction(MachineFunction &MF) {
47  bool Changed = false;
48  const TargetLowering *TLI = MF.getTarget().getTargetLowering();
49
50  // Iterate through each instruction in the function, looking for pseudos.
51  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
52    MachineBasicBlock *MBB = I;
53    for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
54         MBBI != MBBE; ) {
55      MachineInstr *MI = MBBI++;
56
57      // If MI is a pseudo, expand it.
58      if (MI->usesCustomInsertionHook()) {
59        Changed = true;
60        MachineBasicBlock *NewMBB =
61          TLI->EmitInstrWithCustomInserter(MI, MBB);
62        // The expansion may involve new basic blocks.
63        if (NewMBB != MBB) {
64          MBB = NewMBB;
65          I = NewMBB;
66          MBBI = NewMBB->begin();
67          MBBE = NewMBB->end();
68        }
69      }
70    }
71  }
72
73  return Changed;
74}
75