ExpandISelPseudos.cpp revision e837dead3c8dc3445ef6a0e2322179c57e264a13 
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    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
45char ExpandISelPseudos::ID = 0;
46INITIALIZE_PASS(ExpandISelPseudos, "expand-isel-pseudos",
47                "Expand CodeGen Pseudo-instructions", false, false)
48
49FunctionPass *llvm::createExpandISelPseudosPass() {
50  return new ExpandISelPseudos();
51}
52
53bool 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}
83