ExtractFunction.cpp revision d1a85a744cc1001c2b7fc37cf37aca266964f519 
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/Constant.h"
10#include "llvm/Module.h"
11#include "llvm/PassManager.h"
12#include "llvm/Pass.h"
13#include "llvm/Type.h"
14#include "llvm/Analysis/Verifier.h"
15#include "llvm/Transforms/IPO.h"
16#include "llvm/Transforms/Scalar.h"
17#include "llvm/Transforms/Utils/Cloning.h"
18#include "Support/CommandLine.h"
19
20bool DisableSimplifyCFG = false;
21
22namespace {
23  cl::opt<bool>
24  NoADCE("disable-adce",
25         cl::desc("Do not use the -adce pass to reduce testcases"));
26  cl::opt<bool>
27  NoDCE ("disable-dce",
28         cl::desc("Do not use the -dce pass to reduce testcases"));
29  cl::opt<bool, true>
30  NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
31         cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
32  cl::opt<bool>
33  NoFinalCleanup("disable-final-cleanup",
34                 cl::desc("Disable the final cleanup phase of narrowing"));
35}
36
37/// deleteInstructionFromProgram - This method clones the current Program and
38/// deletes the specified instruction from the cloned module.  It then runs a
39/// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
40/// depends on the value.  The modified module is then returned.
41///
42Module *BugDriver::deleteInstructionFromProgram(Instruction *I,
43                                                unsigned Simplification) const {
44  Module *Result = CloneModule(Program);
45
46  BasicBlock *PBB = I->getParent();
47  Function *PF = PBB->getParent();
48
49  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
50  std::advance(RFI, std::distance(Program->begin(), Module::iterator(PF)));
51
52  Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
53  std::advance(RBI, std::distance(PF->begin(), Function::iterator(PBB)));
54
55  BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
56  std::advance(RI, std::distance(PBB->begin(), BasicBlock::iterator(I)));
57  I = RI;                                 // Got the corresponding instruction!
58
59  // If this instruction produces a value, replace any users with null values
60  if (I->getType() != Type::VoidTy)
61    I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
62
63  // Remove the instruction from the program.
64  I->getParent()->getInstList().erase(I);
65
66  // Spiff up the output a little bit.
67  PassManager Passes;
68  if (Simplification > 2 && !NoADCE)
69    Passes.add(createAggressiveDCEPass());          // Remove dead code...
70  //Passes.add(createInstructionCombiningPass());
71  if (Simplification > 1 && !NoDCE)
72    Passes.add(createDeadCodeEliminationPass());
73  if (Simplification && !DisableSimplifyCFG)
74    Passes.add(createCFGSimplificationPass());      // Delete dead control flow
75
76  Passes.add(createVerifierPass());
77  Passes.run(*Result);
78  return Result;
79}
80
81/// performFinalCleanups - This method clones the current Program and performs
82/// a series of cleanups intended to get rid of extra cruft on the module
83/// before handing it to the user...
84///
85Module *BugDriver::performFinalCleanups(Module *InM) const {
86  Module *M = InM ? InM : CloneModule(Program);
87
88  // Allow disabling these passes if they crash bugpoint.
89  //
90  // FIXME: This should eventually run these passes in a pass list to prevent
91  // them from being able to crash bugpoint at all!
92  //
93  if (NoFinalCleanup) return M;
94
95  // Make all functions external, so GlobalDCE doesn't delete them...
96  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
97    I->setLinkage(GlobalValue::ExternalLinkage);
98
99  PassManager CleanupPasses;
100  CleanupPasses.add(createFunctionResolvingPass());
101  CleanupPasses.add(createGlobalDCEPass());
102  CleanupPasses.add(createDeadTypeEliminationPass());
103  CleanupPasses.add(createDeadArgEliminationPass(InM == 0));
104  CleanupPasses.add(createVerifierPass());
105  CleanupPasses.run(*M);
106  return M;
107}
108