ExtractFunction.cpp revision 44be25716628941b4cccccf56a28ee0ba2606850 
1//===- ExtractFunction.cpp - Extract a function from Program --------------===//
2//
3// This file implements a method that extracts a function from program, cleans
4// it up, and returns it as a new module.
5//
6//===----------------------------------------------------------------------===//
7
8#include "BugDriver.h"
9#include "llvm/Module.h"
10#include "llvm/PassManager.h"
11#include "llvm/Transforms/IPO.h"
12#include "llvm/Transforms/Scalar.h"
13#include "llvm/Transforms/Utils/Cloning.h"
14#include "llvm/Analysis/Verifier.h"
15#include "llvm/Type.h"
16#include "llvm/Constant.h"
17
18/// deleteInstructionFromProgram - This method clones the current Program and
19/// deletes the specified instruction from the cloned module.  It then runs a
20/// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
21/// depends on the value.  The modified module is then returned.
22///
23Module *BugDriver::deleteInstructionFromProgram(Instruction *I,
24                                                unsigned Simplification) const {
25  Module *Result = CloneModule(Program);
26
27  BasicBlock *PBB = I->getParent();
28  Function *PF = PBB->getParent();
29
30  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
31  std::advance(RFI, std::distance(Program->begin(), Module::iterator(PF)));
32
33  Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
34  std::advance(RBI, std::distance(PF->begin(), Function::iterator(PBB)));
35
36  BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
37  std::advance(RI, std::distance(PBB->begin(), BasicBlock::iterator(I)));
38  I = RI;                                 // Got the corresponding instruction!
39
40  // If this instruction produces a value, replace any users with null values
41  if (I->getType() != Type::VoidTy)
42    I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
43
44  // Remove the instruction from the program.
45  I->getParent()->getInstList().erase(I);
46
47  // Spiff up the output a little bit.
48  PassManager Passes;
49  if (Simplification > 2)
50    Passes.add(createAggressiveDCEPass());          // Remove dead code...
51  //Passes.add(createInstructionCombiningPass());
52  if (Simplification > 1)
53    Passes.add(createDeadCodeEliminationPass());
54  if (Simplification)
55    Passes.add(createCFGSimplificationPass());      // Delete dead control flow
56
57  Passes.add(createVerifierPass());
58  Passes.run(*Result);
59  return Result;
60}
61
62/// performFinalCleanups - This method clones the current Program and performs
63/// a series of cleanups intended to get rid of extra cruft on the module
64/// before handing it to the user...
65///
66Module *BugDriver::performFinalCleanups() const {
67  PassManager CleanupPasses;
68  CleanupPasses.add(createFunctionResolvingPass());
69  CleanupPasses.add(createGlobalDCEPass());
70  CleanupPasses.add(createVerifierPass());
71  Module *M = CloneModule(Program);
72  CleanupPasses.run(*M);
73  return M;
74}
75