ExtractFunction.cpp revision 587a6ce4b99346b5e785d0a5c360c6c6687b036a 
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#include "Support/CommandLine.h"
18
19namespace {
20  cl::opt<bool>
21  NoADCE("disable-adce",
22         cl::desc("Do not use the -adce pass to reduce testcases"));
23  cl::opt<bool>
24  NoDCE ("disable-dce",
25         cl::desc("Do not use the -dce pass to reduce testcases"));
26  cl::opt<bool>
27  NoSCFG("disable-simplifycfg",
28         cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
29  cl::opt<bool>
30  NoFinalCleanup("disable-final-cleanup",
31                 cl::desc("Disable the final cleanup phase of narrowing"));
32}
33
34/// deleteInstructionFromProgram - This method clones the current Program and
35/// deletes the specified instruction from the cloned module.  It then runs a
36/// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
37/// depends on the value.  The modified module is then returned.
38///
39Module *BugDriver::deleteInstructionFromProgram(Instruction *I,
40                                                unsigned Simplification) const {
41  Module *Result = CloneModule(Program);
42
43  BasicBlock *PBB = I->getParent();
44  Function *PF = PBB->getParent();
45
46  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
47  std::advance(RFI, std::distance(Program->begin(), Module::iterator(PF)));
48
49  Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
50  std::advance(RBI, std::distance(PF->begin(), Function::iterator(PBB)));
51
52  BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
53  std::advance(RI, std::distance(PBB->begin(), BasicBlock::iterator(I)));
54  I = RI;                                 // Got the corresponding instruction!
55
56  // If this instruction produces a value, replace any users with null values
57  if (I->getType() != Type::VoidTy)
58    I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
59
60  // Remove the instruction from the program.
61  I->getParent()->getInstList().erase(I);
62
63  // Spiff up the output a little bit.
64  PassManager Passes;
65  if (Simplification > 2 && !NoADCE)
66    Passes.add(createAggressiveDCEPass());          // Remove dead code...
67  //Passes.add(createInstructionCombiningPass());
68  if (Simplification > 1 && !NoDCE)
69    Passes.add(createDeadCodeEliminationPass());
70  if (Simplification && !NoSCFG)
71    Passes.add(createCFGSimplificationPass());      // Delete dead control flow
72
73  Passes.add(createVerifierPass());
74  Passes.run(*Result);
75  return Result;
76}
77
78/// performFinalCleanups - This method clones the current Program and performs
79/// a series of cleanups intended to get rid of extra cruft on the module
80/// before handing it to the user...
81///
82Module *BugDriver::performFinalCleanups(Module *InM) const {
83  Module *M = InM ? InM : CloneModule(Program);
84
85  // Allow disabling these passes if they crash bugpoint.
86  //
87  // FIXME: This should eventually run these passes in a pass list to prevent
88  // them from being able to crash bugpoint at all!
89  //
90  if (NoFinalCleanup) return M;
91
92  // Make all functions external, so GlobalDCE doesn't delete them...
93  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
94    I->setLinkage(GlobalValue::ExternalLinkage);
95
96  PassManager CleanupPasses;
97  CleanupPasses.add(createFunctionResolvingPass());
98  CleanupPasses.add(createGlobalDCEPass());
99  CleanupPasses.add(createDeadTypeEliminationPass());
100  CleanupPasses.add(createDeadArgEliminationPass(InM == 0));
101  CleanupPasses.add(createVerifierPass());
102  CleanupPasses.run(*M);
103  return M;
104}
105